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pobierz - Drewno

INSTYTUT TECHNOLOGII DREWNA
WOOD TECHNOLOGY INSTITUTE
DREWNO
PRACE NAUKOWE ● DONIESIENIA
KOMUNIKATY
WOOD
RESEARCH PAPERS ● REPORTS ● ANNOUNCEMENTS
Vol. 54
POZNAŃ 2011
Nr 185
Wydanie publikacji dofinansowane przez Ministerstwo Nauki i Szkolnictwa Wyższego
The journal is financially supported by Polish Ministry of Science and Higher Educations
Recenzenci (Reviewers): dr inż. Mariusz Jóźwiak, dr Grzegorz Kowaluk, dr Zofia Krzoska-Adamczak, mgr inż. Andrzej Noskowiak, mgr Magdalena Nowaczyk-Organista, dr
inż. Grzegorz Pajchrowski, prof. dr hab. Stanisław Proszyk, dr inż. Agata Stachowiak-Wencek, prof. nadzw. dr hab. Jadwiga Zabielska-Matejuk, prof. dr hab. Roman Zakrzewski
Publikacje indeksowane są w bazach danych (Publications are indexed in the databases): Science Citation Index Expanded – http://thomsonreuters.com, SCOPUS –
http://www.scopus.com, BazTech – http://baztech.icm.edu.pl, DREWINF – http://www.
itd.poznan.pl, The Central European Journal of Social Sciences and Humanities – http://
cejsh.icm.edu.pl
Artykuły polskojęzyczne zawierają streszczenia w języku angielskim, a obcojęzyczne –
w języku polskim. Spisy treści, streszczenia i pełne teksty artykułów są dostępne na stronie www.itd.poznan.pl/pl/drewno
Prace naukowe i doniesienia uzyskują 6 punktów według klasyfikacji MNiSW.
Polish language articles have summaries in English language, and foreign language articles have summaries in Polish language. Tables of contents, summaries, and full versions
of the articles are available at www.itd.poznan.pl/en/wood
Wydawca (Editorial Office): Instytut Technologii Drewna
ul. Winiarska 1, 60-654 Poznań, Polska (Poland)
Adres Redakcji (Publishers’ address): Instytut Technologii Drewna
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tel. +48/61 849 24 01, +48/61 849 24 61, fax +48/61 822 43 72,
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© Copyright by Instytut Technologii Drewna w Poznaniu
Poznań 2011
ISSN 1644-3985
Projekt okładki (Cover design): Piotr Gołębniak
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Skład komputerowy (Computer typesetting): BookArt Poznań
Druk (Print): Studio Poligrafia, ul. Bułgarska 10, 60-321 Poznań, tel. 61 867 53 72
Nakład (Edition): 520 egz.
SPIS TREŚCI – CONTENTS
Prace naukowe – Research papers
Boštjan Lesar, Andrijana Sever Škapin, Miha Humar: The influence of drying
on the sorption properties of polyethylene wax treated wood (Wpływ suszenia na właściwości sorpcyjne drewna impregnowanego woskiem polietylenowym) ......................................................................................................
5
Srečko Vratuša, Manja Kitek Kuzman, Vojko Kilar: Structural particulars of
glued laminated beams of variable height (Specyfika strukturalna klejonych
warstwowo belek o zmiennej wysokości) ......................................................
19
Jānis Iejavs, Uldis Spulle, Vilnis Jakovļevs: The comparison of properties of
three-layer cellular material and wood-based panels (Porównanie właściwości trzywarstwowego materiału komórkowego oraz płyt drewnopochodnych) .............................................................................................................
39
Agnieszka Jankowska, Magdalena Szczęsna: The study of colour changes of
chosen species of wood from Southeast Asia caused by transparent coatings
and exposure to sunlight (Badanie zmian barwy wybranych gatunków
drewna z Azji Południowo-Wschodniej spowodowanych transparentnymi
powłokami i oddziaływaniem światła słonecznego) .....................................
51
Jarosław Banecki: Comparative studies of furniture lacquer coatings’ resistance to linear scratching acc. to the method described in TS 15186:2005
(Badania porównawcze odporności meblowych pokryć lakierowych na zarysowanie prostoliniowe z zastosowaniem metody według TS 15186:2005)
61
Grzegorz Kowaluk, Magdalena Komorowicz, Magdalena Witczak, Dorota
Fuczek: Formaldehyde content in and VOC release from particleboards
made of fibrous chips (Zawartość formaldehydu i emisja VOC płyt wiórowych wytworzonych z wiórów włóknistych) .............................................
81
Doniesienia naukowe – Research reports
Magdalena Witczak, Małgorzata Walkowiak, Wojciech Cichy: Pre-treatment of biomass by torrefaction – preliminary studies (Toryfikacja jako
proces obróbki biomasy – badania wstępne) ..............................................
89
Marcin Oszust, Daniel Pieniak, Paweł Ogrodnik, Lesław Dec: Badanie spadku
wytrzymałości drewna świerkowego modyfikowanego termicznie w warunkach temperatur pożarowych (The investigation of immediate strength
loss of thermally modified spruce timber under fire temperatures) ............
97
Inokentijs Lipinskis, Uldis Spulle: Research on mechanical properties of birch
plywood with special veneer lay-up schemes (Badania właściwości mechanicznych wodoodpornej sklejki brzozowej o zróżnicowanym układzie
fornirów) ....................................................................................................... 109
Miloš Hitka, Mária Sirotiakovà: The impact of economic crisis on the change
in motivation of furniture company employees – case study (Wpływ kryzysu
gospodarczego na zmianę motywacji pracowników zatrudnionych w firmie
meblarskiej – studium przypadku) ............................................................... 119
Komunikaty – Announcements
Ewa Ratajczak: Osiągnięcia Instytutu Technologii Drewna w obszarze badań
czwartorzędowych soli amoniowych (The achievements of the Wood Technology Institute in the area of research on quaternary ammonium salts) .... 127
Dorota Fuczek, Magdalena Czajka: 7. Europejskie sympozjum płyt drewnopochodnych (The 7th European wood-based panel symposium) ................. 131
Grzegorz Kowaluk: The issues of wood processing on the 7th International
Science Conference “Chip and Chipless Woodworking Processes” (Problematyka przerobu drewna na 7. Międzynarodowej Konferencji Naukowej
„Chip and Chipless Woodworking Processes” .......................................... 135
Władysław Strykowski: Sprawozdanie z corocznej konferencji Europejskiego
Instytutu Leśnego (Report on the annual conference of the European Forest Institute) ................................................................................................. 137
Działalność naukowa profesora Ryszarda Babickiego ....................................... 139
Drewno. Pr. Nauk. Donies. Komunik. 2011, vol. 54, nr 185
PRACE NAUKOWE - RESEARCH PAPERS
Boštjan Lesar, Andrijana Sever Škapin, Miha Humar
THE INFLUENCE OF DRYING ON THE SORPTION
PROPERTIES OF POLYETHYLENE WAX TREATED
WOOD
The importance of the use of waxes in the wood industry has been increasing, particularly in Europe, since consumers, due to their increased environmental awareness, avoid using biocidally treated wood and wood from tropical forests. In this
research two water-repellent emulsions in various concentrations were used: polyethylene and oxidised polyethylene wax emulsion. The performance of wax treated
Norway spruce (Picea abies) and beech (Fagus sylvatica) wood was tested in two
sorption experiments: conditioning in high relative air humidity (vapour diffusion)
and non-continuous dipping (liquid flow). The sorption properties of oven and vacuum dried impregnated specimens were determined. During conditioning, wax
treated Norway spruce specimens, vacuum and oven dried, had the same moisture
content as control specimens; while treated vacuum dried beech had up to 25% lower moisture content than the parallel control specimens. An even higher difference
was evident in volume changes of vacuum and oven dried beech specimens during
the sorption test.
Keywords: beech, Norway spruce, polyethylene wax, sorption, wood preservation,
water repellents1
Introduction
Wood is the most important biopolymer in the world. It is also the most important natural material used for construction applications. As a natural material, it is
exposed to weathering and biotic decay. In order to use wood in outdoor applicaBoštjan Lesar, University of Ljubljana, Slovenia
Andrijana Sever Škapin, Slovenian National Building and Civil Engineering Institute,
Ljubljana, Slovenia
Miha Humar, University of Ljubljana, Slovenia
6
tions, it has to be protected somehow. In the past, most preservative solutions had
biocidal properties and therefore inhibited pest growth [Richardson 1993]. Future solutions improving durability of wood preservatives are designed differently.
They change the structure of wood so that wood pests do not recognise it as a food
source [Tjeerdsma et al. 1998]; alternatively, wood moisture content is kept at such
a low level that decay processes are no longer possible [Goethals, Stevens 1994].
The treatment of wood with water repellents can affect the long-term properties
of this material. Impregnation of wood with resins, waxes, silicones, coatings and
other water-repellent formulations greatly reduces the rate of water flow in the capillaries and significantly increases dimensional stability of specimens exposed to
wet conditions [Berninghausen et al. 2006; Kurt et al. 2008]. The most important
applications of waxes in the wood industry are therefore found in particleboard
production. Paraffin emulsions are introduced into particleboards in order to reduce water uptake and improve dimensional stability [Amthor 1972]. However,
there are reports that paraffin treatment can also reduce the water capillary uptake
in wood [Scholz et al. 2009]. Furthermore, wax treated wood demonstrates increased compression strength and hardness [Rapp et al. 2005]. In addition, wax and
oil emulsion additives are incorporated into aqueous wood preservatives to reduce
checking and improve the appearance of treated wood used outdoors [Evans et al.
2009]. However, paraffin, montan wax or synthetic waxes do not react with wood.
They either form thin films on the surface of wood or on the surface of cell walls,
or they fill the cell lumina with waxes and thus limit water penetration into wood.
Since they are insoluble in water, they do not leach from wood [Berninghausen
et al. 2006].
The importance of the use of waxes in the wood protection industry has been
increasing, particularly in Europe, since consumers, due to their increased environmental awareness, avoid biocidally treated wood and wood from non-sustainable tropical forests. The industry is therefore interested in development of alternatives, such as treatment with waxes. There are at least two commercially used
wax treatments of wood (Dauerholz in Germany and Natwood in Austria). Nowadays, synthetic waxes, which are used in various coatings, have been becoming
more and more important in the wood industry. They have some advantages over
natural waxes: they are cheaper and their properties (melting point) can be set
during production [Wolfmeier 2003]. Among the most promising waxes for potential applications in the field of wood protection are polyethylene waxes, which
considerably slow down fungal degradation of impregnated Norway spruce or
beech wood [Lesar, Humar 2010]. They also can be used as water repellents, since they decrease water uptake up to 5 times in a short submersion test. However,
it was indicated in previous preliminary research that heating or curing wax treated wood affected the wood sorption properties. The present research was conducted in order to elucidate the effect of heating of wax emulsion treated wood
above the melting point on the sorption properties of the treated wood.
The influence of drying on the sorption properties of polyethylene wax treated wood
7
Material and methods
Samples (2.0 cm × 2.0 cm × 5 cm) made of Norway spruce (Picea abies) and beech (Fagus sylvatica) were vacuum/pressure impregnated with various preservative solutions according to the full cell process (20 min -0.9 bar vacuum, 1.5 hour
pressure 8 bar, 10 min -0.8 bar vacuum). All specimens had end-sealed (Epoxy
coating, EPOLOR, Color) axial surfaces before impregnation. However, sealing
needed to be reapplied after the treatment, since some cracks formed. After impregnation, the retention of the preservative solution was determined gravimetrically.
The preservative solutions used consisted of aqueous emulsion of polyethylene
(WE1) and aqueous emulsion of oxidised polyethylene (WE6) wax. Wax emulsions were purchased from BASF (Germany). The concentrations (dry content) of
the wax emulsions are given in table 1. Wax emulsions of two different concentrations were used for impregnation: WE1-A and WE6-A emulsions contained 25%
of the original emulsions; while WE1-B and WE6-B emulsions contained 50% of
the original emulsions. Control specimens were left un-impregnated and also had
end-sealed axial surfaces. After three weeks of conditioning at room temperature, half of the impregnated and half of the un-impregnated specimens were oven
dried for 21 hours at 103 ± 2 °C and 3 hours above the melting point of the waxes
used (140 ± 2°C) [Anonymous 2004a; Anonymous 2004b]. Specimens were cured for 3 hours, which ensured that even the centre of the specimens was heated
above 135°C for one hour, as determined by a temperature sensor (EL-USB-TC
Lascar Electronics, United Kingdom). The other half of the specimens were vacuum dried (-0.75 bar) at 60°C in a vacuum chamber (Kambič, Slovenia) for 24
hours. The samples were then conditioned in room conditions (21°C and 65%
RH) for two weeks.
Table 1. Dry content of waxes used and their retention in Norway spruce and beech
wood after vacuum pressure impregnation
Tabela 1. Sucha masa zastosowanych wosków i ich retencja w drewnie świerka pospolitego
i buka po impregnacji próżniowej
Emulsja woskowa
Wax emulsion
Stężenie (%)
Conc. (%)
Dry content %
WE1-A
WE1-B
WE6-A
WE6-B
25
50
25
50
8.2
16.5
8.3
17.8
WE1-A
WE1-B
WE6-A
WE6-B
25
50
25
50
8.2
16.5
8.3
17.8
Sucha masa %
Wood
Drewno
Spruce
Świerk
Beech
Buk
Retention kg/m3
Retencja kg/m3
197 (67)
138 (56)
189 (35)
135 (27)
689 (24)
641 (78)
683 (31)
679 (40)
8
In order to determine the sorption properties, two types of tests were performed: the vapour diffusion test and the liquid penetration test. In order to elucidate
vapour diffusion, half of the oven dried and half of the vacuum dried specimens
were transferred to a chamber with a relative air humidity (RH) of 87%. The
masses and dimensions of the specimens were monitored for 41 days according to
predetermined periods (fig. 1, 2).
Fig. 1. Moisture content during moisturising in 87 % humidity environment of polyethylene wax emulsion treated: (a) vacuum dried spruce, (b) spruce cured at 140 °C,
(c) vacuum dried beech, and (d) beech cured at 140°C
Rys. 1. Wilgotność podczas nawilżania przy 87% wilgotności otoczenia impregnowanego
emulsją wosku polietylenowego: (a) świerka suszonego próżniowo, (b) świerka utwardzanego w temp. 140 °C, (c) buka suszonego próżniowo i (d) buka utwardzanego w temp. 140°C
9
Fig. 2. SEM images of the surface of un-cured (a) and cured (b) WE6-B impregnated
Norway spruce specimens
Rys. 2. Obraz SEM powierzchni próbek świerka pospolitego impregnowanych WE6-B nieutwardzonych (a) i utwardzonych (b)
Fig. 3. Volume changes during moisturising in 87% humidity environment of polyethylene wax emulsion treated: (a) vacuum dried spruce, (b) spruce cured at 140 °C,
(c) vacuum dried beech, and (d) beech cured at 140°C
Rys. 3. Zmiany objętości podczas nawilżania przy 87% wilgotności otoczenia impregnowanego emulsją wosku polietylenowego: (a) świerka suszonego próżniowo, (b) świerka utwardzanego w temp. 140 °C, (c) buka suszonego próżniowo i (d) buka utwardzanego w temp. 140°C
10
Fig. 4. Moisture content of polyethylene wax emulsion treated: (a) vacuum dried
spruce, (b) spruce cured at 140 °C, (c) vacuum dried beech, and (d) beech cured at
140°C, before 10 minute non-continuous dipping in water
Rys. 4. Wilgotność impregnowanego emulsją wosku polietylenowego: (a) świerka suszonego próżniowo, (b) świerka utwardzanego w temp. 140 °C, (c) buka suszonego próżniowo
i (d) buka utwardzanego w temp. 140°C, przed 10-minutowym przerywanym zanurzaniem
w wodzie
11
Fig. 5. Moisture content of polyethylene wax emulsion treated: (a) vacuum dried
spruce, (b) spruce cured at 140 °C, (c) vacuum dried beech, and (d) beech cured at
140°C, after 10 minute non-continuous dipping in water
Rys. 5. Wilgotność impregnowanego emulsją wosku polietylenowego: (a) świerka suszonego
próżniowo, (b) świerka utwardzanego w temp. 140 °C, (c) buka suszonego próżniowo i (d)
buka utwardzanego w temp. 140°C, po 10-minutowym przerywanym zanurzaniu w wodzie
12
Fig. 6. Volume changes of polyethylene wax emulsion treated: (a) vacuum dried spruce, (b) spruce cured at 140 °C, (c) vacuum dried beech, and (d) beech cured at 140°C,
during non-continuous dipping in water
Rys. 6. Zmiany objętości impregnowanego emulsją wosku polietylenowego: (a) świerka suszonego próżniowo, (b) świerka utwardzanego w temp. 140 °C, (c) buka suszonego próżniowo i (d) buka utwardzanego w temp. 140°C, podczas przerywanego zanurzania w wodzie
In the second part of the experiment, the interest was in liquid penetration
and drying of impregnated wood. The other half of the specimens intended for
water uptake analysis were immersed in distilled water for 10 minutes on the 1st,
2nd, 3th, 4th, 7th, 9th, 10th, 11th, 14th,16th, 17th and 18th day. The masses and
dimensions of the specimens were monitored before and after immersion (fig. 3,
4, 5). Dimensions were measured with laser equipment (Department of Wood
Science and Technology, Slovenia). Both sorption experiments were performed
on ten identical specimens per emulsion/wood species/drying.
A SEM microscope (JEOL 5500 LV, Japan) was used for surface observation.
Wax impregnated and control specimens were coated with a highly conductive
13
film of gold (Sputter Coater SCD 005, Baltec, Germany). Specimens were scanned in high vacuum and an accelerating voltage of 20 kV was used.
Results and discussion
As a result of the impregnation process, Norway spruce specimens retained between 135 kg/m3 and 197 kg/m3 of the emulsions. In contrast, beech specimens
retained considerably higher amounts of the emulsions. In general, they retained
between 641 kg/m3 and 689 kg/m3 of wax emulsions (table 1). This result is reasonable as beech wood is significantly more permeable than spruce. It is clearly
evident that retention in Norway spruce wood was influenced by the emulsion
type and the dry content of the wax. The main reason for this is that the particles
in the emulsions are too big (100 nm) [Anonymous 2004a; Anonymous 2004b] to
penetrate the cell walls; they even form a barrier on the surface of the cell wall and
reduce the penetration of the solvent (water) into the cell walls.
However, the most important focus of the research was to elucidate how polyethylene wax emulsions influence the sorption properties of the impregnated
wood. The first set of sorption experiments was performed in a chamber with 87%
RH, in which impregnated specimens were conditioned. Half of the specimens
were oven dried (140 °C) and the other half were vacuum dried (60 °C). The
moisture content (MC) of various control specimens reached equilibrium moisture content (EMC) at approximately 15% after 17 days of conditioning (fig. 1a,
1b, 1c, 1d). Surprisingly, there were no significant differences in the process of
moisturising and the final MC after 41 days of conditioning of vacuum and oven
dried control and impregnated Norway spruce specimens (fig. 1a, 1b). It is presumed that the reason for this was the low retention of wax emulsions in spruce
wood [Lesar, Humar 2010; Lesar et al. 2010]. Furthermore, there were also almost
no differences in the MC of oven dried control and wax treated beech specimens
(fig. 1d). On the other hand, the most prominent vapour barrier was formed by
wax treated, vacuum dried beech. Those specimens demonstrated lower MC than
control specimens. The lowest final MC was determined for WE6-B impregnated,
vacuum dried beech specimens, whose MC was 25 % lower than the MC of control specimens (fig. 1c). Those results were not in line with the expectations. It had
been expected that vacuum dried control and wax treated specimens would have
a higher MC than the oven dried. The finding was in contradiction with two things.
Firstly, thermal decomposition of wood begins at temperatures above 100°C [LeVan 1989; Esteves, Pereira 2009], resulting in decomposition of hemicelluloses
[Fengeland, Wegener 1989; Orfao, Figueiredo 2001], which are the most hygroscopic wood component [Skaar 1972]. Thus ,in general heat treated wood has
a lower MC in the process of conditioning than non-heated wood. Secondly, curing above the melting point led to the formation of a compact film of wax on the
14
wood surface, as can be clearly seen in fig. 2. Therefore, there must have been
some voids in that wax film which facilitated diffusion of water vapour. However,
it must be taken into account that wax itself is not hydroscopic, since the moisture
content of the wax at 98% relative air humidity varied between 1.1% and 1.3%,
so the sorption properties of wood must be the factor that determines the sorption
properties of the wax-wood complex.
The differences in volume changes of wax treated and control specimens were
very noticeable. Fig. 3 presents volume changes that occurred during exposure
of control and wax treated specimens in a chamber with RH of 87%. The shape
of the volume change curve during moisturising is similar to the curve of moisture changes. The differences in volume changes of vacuum and oven dried
control and wax treated Norway spruce specimens were insignificant, with the
exception of vacuum dried WE6-A impregnated specimens, the swelling of which
was considerably more prominent than the swelling of control specimens (fig. 3a,
3b). In contrast, all wax treated beech specimens, regardless of the type of drying
applied, had up to 40% improved dimensional stability in comparison to control
specimens. Furthermore, a difference was observed in the dimension changes of
vacuum dried and oven dried specimens. Surprisingly, the volume changes of impregnated oven dried beech specimens were smaller than dimensional changes of
control specimens in terms of moisture content during the test (fig. 1d, 2d). These
results indicate that polyethylene wax was to some extent bound in the cell walls
of wood [Banks 1973], which prevented swelling of treated wood. The results
were in contradiction to those of Rowell and Banks [1985], who reported that
water repellents cannot, to any significant extent, interfere with the movement of
water into wood by vapour-phase or bound water mechanisms.
In the second set of sorption experiments, control and treated specimens were
being dipped in and taken out of distilled water for a period of 10 minutes in order
to simulate occasional wetting that occurs in service life. The moisture content of
vacuum dried control spruce specimens before immersion varied between 5.4%
and 8.5%. The MC of vacuum dried control beech specimens was between 4.8%
and 10.8% (fig. 4a, 4c). The MC of wood specimens before immersion depended mostly on the drying time between immersion events. The MC of oven dried
Norway spruce and beech control specimens before immersion increased from
1.0% to 7.0% (fig. 4a, 4b, 4c, 4d). Surprisingly, wax treated Norway spruce and
beech specimens demonstrated higher MC than control specimens. The type of
wax emulsions used for the impregnation of spruce did not have any significant
influence on the moisture content of the impregnated wood before immersion.
The shape of the curve of MC changes of treated vacuum dried beech specimens
before their impregnation with wax was similar to that of vacuum dried Norway
spruce specimens, but in general the MC of wax treated beech specimens was
higher (fig. 4a, 4c). In all cases oven dried control and wax treated specimens had
similar MC at the beginning of the immersion test.
15
After the immersion events, the MC of all specimens was similar to the reported in the previous chapter, although all values were considerably higher. The MC
of vacuum dried Norway spruce control specimens increased by approximately
5 percent on average after immersion. The moisture content of the specimens
increased during the tests. For example, the MC of vacuum dried beech control
specimens was 9.3% after the first immersion and increased up to 20.5% after
the last immersion. Surprisingly, impregnation of spruce wood with waxes did
not improve water repellence but, on the contrary, in certain cases even made the
wood hydrophilic. The MC of wax treated vacuum dried Norway spruce specimens was nearly 150% higher than that of control specimens. The influence of
wax treatment on water uptake during immersion was even more prominent in
the case of beech specimens (fig. 5a, 5c). The comparison of the oven dried and
vacuum dried wax treated beech specimens clearly indicates that polyethylene
waxes (WE1 and WE6 of both concentrations) had to be cured (heated) above the
wax melting point in order for the surfaces of the treated specimens to have become hydrophobic. It is presumed that the main reason for this was the morphology
of the wax surface on wood. In the case of vacuum dried specimens, there were
small cracks on the surfaces of polyethylene wax impregnated wood samples (fig.
2a). The cracks acted as capillaries, which took up water and reduced the contact
angles of the surfaces [de Meijer, Militz, 2000]. The contact angle of water on
vacuum dried WE6 treated wood was about 10°. This made penetration of water
into the wood considerably faster. However, after curing above the melting point
polyethylene wax formed a compact thin film which repelled water. This can be
clearly seen in the SEM figure (fig. 2b). However, it must be taken into account
that oven drying at 140°C has some effect on the material. The MCs of oven dried
Norway spruce and beech control specimens increased during the experiment and
were approximately 4 percent higher than before immersion. After the last immersion, the MC of spruce specimens was 12.5% and of beech specimens 12.0%.
This is reasonable, since heat treatment is a well-established technology for wood
modification [Esteves, Pereira 2009]. However, a combination of wax treatment
and oven drying was even more effective. WE1-A, WE1-B, WE6-A treated oven
dried Norway spruce specimens had lower MC than control specimens (WE6-A
up to 15%) (fig. 5b). WE6-B treated specimens had the lowest MC among oven
dried beech specimens; MC was on average 18% lower than that determined for
parallel control specimens (fig. 5d). The weak hydrophobic efficacy of polyethylene waxes did not reduce the shrinking or swelling of wood. The differences
between vacuum dried control and wax treated spruce and beech specimens were
insignificant (fig. 5a, 5b, 5c, 5d).
From the results presented in this research, it can be seen that vacuum drying
of wax treated wood was not so effective a hydrophobic treatment as oven drying
of wax treated wood. As already mentioned, the main reason for the higher MC
of vacuum dried specimens was the small cracks visible on the surface of WE6
16
and WE1 treated wood. The small cracks on the surface of vacuum dried treated
wood formed capillaries which increased water flow [de Meijer, Militz 2000]. It is
also known that some liquid water flow may occur in water repellent treated specimens due to the phenomenon of preferential wetting of wood surfaces by water
[Banks 1973]. A reduction in the MC of polyethylene wax treated Norway spruce
and beech specimens was only achieved with oven drying at temperatures above
the melting points of waxes. After drying the wax treated wood above the melting
point, polyethylene (WE1) and oxidised polyethylene (WE6) wax formed a film
which prevented fast water penetration into the treated wood and also facilitated
fast drying of that material after dipping (fig. 2b). The lower moisture content of
oven dried wax treated Norway spruce and beech specimens during dipping in
water did not result in improved dimensional stability. Rowell and Banks [1985]
reported that water repellent treated wood exposed to liquid water for a prolonged
period, not only would swell to the same extent as similar untreated wood but also
accumulate free water in the cell luminas and therefore eventually attain a MC in
excess of fibre saturation. This is in line with the findings presented hereinbefore.
Conclusions
The sorption properties of polyethylene (WE1) and oxidised polyethylene wax
(WE6) were influenced by its retention. Lower retention of the wax by Norway
spruce compared to beech specimens led to smaller differences between the MC
of treated and control specimens during conditioning in humid air and moisturising during non-continuous dipping in water. During conditioning in humid air,
a positive effect of wax treatment was observed only on vacuum dried treated
beech specimens. Improved dimensional stability was found only in the case of
oven dried beech. In order to achieve slower water penetration into wax treated
wood during dipping in water, the wax treated material had to be oven dried above
the melting point of the wax used. Furthermore, the results clearly indicate that
polyethylene wax treatment slowed down drying of oven dried Norway spruce
and beech specimens.
Acknowledgments
The authors would like to thank the Slovenian Research Agency for financial support under projects L4-0820-0481 and P4-0015-0481. The technical support of
Matej Grilc is also gratefully acknowledged.
17
References
Amthor J. [1972]: Paraffin dispersions for waterproofing of particle board. Holz als Roh-und
Werkst. [30]-11: 422-425
Anonymus [2004a]: Poligen WE1, Technical information. www.basf.de, (5.12. 2008)
Anonymus [2004b]: Poligen WE6, Technical information. www.basf.de, (5.12. 2008)
Banks W.B. [1973]: Water uptake by Scots Pine Sapwood, and its Restriction by the Use of
Water Repellents. Wood Science and Technology 7:271-284
Berninghausen C.G., Rapp A.O., Welzbacher C.R. [2006]: Impregnating agent, process for
impregnating of dried and profiled wood, and wood product impregnated therewith. Patent
EP1660285
Fengel D., Wegener G. [1989]: Wood, Chemistry, Ultrastructure, Reactions Walter de Gruyter,
Berlin, New York
de Meijer M., Militz H. [2000]: Moisture transport in coated wood. Part 1: Analysis of sorption rates and moisture content profiles in spruce during liquid water uptake. Holz als
Roh-und Werkst. 58:354-362
Esteves B.M., Pereira H. M. [2009]: Wood Modification by Heat Treatment: a Review. Bioresources 4:370-404
Evans P.D., Wingate-Hill R., Cunningham R.B. [2009]: Wax and oil emulsion additives:
How effective are they at improving the performance of preservative-treated wood? Forest
Products Journal 59: 66-70
Kurt R., Krause A., Militz H., Mai C. [2008]: Hydroxymethylated resorcinol (HMR) priming agent for improved bondability of wax-treated wood. Holz als Roh-und Werkst.
[66]5:333-338
Lesar B., Humar M. [2010]: Use of wax emulsions for improvement of wood durability and
sorption properties. European Journal of Wood and Wood Products. DOI 10.1007/s00107010-0425-y
Lesar B., Straže A., Humar M. [2010]: Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion. Journal of Applied Polymer Science
(in press)
LeVan S.L. [1989]: Thermal degradation. In Concise Encyclopedia of Wood & Wood-Based
Materials Ed. S. A.P. Pergamon Press. New York: 271-273
Orfao J.J.M., Figueiredo J.L. [2001]: A simplified method for determination of lignocellulosic materials pyrolysis kinetics from isothermal thermogravimetric experiments. Thermochimica Acta 380:67-78
Rapp A.O., Beringhausen C., Bollmus S., Brischke C., Frick T., Haas T., Sailer M., Welzbacher C.R. [2005]: Hydrophobierung von Holz-Erfahrungen nach 7 Jahren Freilandtest. In: 24th Holzschutztagung der DGFH, Leipzig: 157-170
Richardson B.A. [1993]: Wood Preservation. Second edition. E & FN Spon, London, Glasgow
Rowell R.M., Banks W.B. [1985]: Water Repellency and Dimensional Stability of Wood. Gen.
Tech. Rep. FPL Forest products Laboratory
Scholz G., Krause A., Militz H. [2009]: Capillary Water Uptake and Mechanical Properties of
Wax Soaked Scots Pine.in: 4th European Conference on Wood Modification, Stockholm:
209-212
Skaar C. [1972]: Water in wood. Syracuse University Press, New York
Tjeerdsma B.F., Boonstra M., Militz H. [1998]: Thermal modification of non-durable wood
species 2. Improved wood properties of thermally treated wood. The International Research Group on Wood Preservation. Document. IRG/WP 98-40124
WolfmeierU., Waxes V. [2003]: Ullman’s encyclopedia of industrial chemistry. Vol. 39, 3.
Edition (Ed.), Bhonet M. Wiley-VCH. Weinheim: 136-141
18
WPŁYW SUSZENIA NA WŁAŚCIWOŚCI SORPCYJNE DREWNA
IMPREGNOWANEGO WOSKIEM POLIETYLENOWYM
Streszczenie
Znaczenie zastosowania wosków w przemyśle drzewnym rośnie, zwłaszcza w Europie,
co spowodowane jest wzrostem świadomości ekologicznej, niechęcią konsumentów
do używania drewna poddanego obróbce biocydami oraz drewna z lasów tropikalnych.
W badaniach wykorzystano dwie emulsje wodoodporne o różnych stężeniach: polietylenową emulsję woskową i jej utlenioną wersję. Właściwości impregnowanego woskiem
drewna świerka pospolitego (Picea abies) i drewna buka (Fagus sylvatica) zostały przebadane w trakcie badań sorpcji: klimatyzowania w warunkach wysokiej wilgotności
względnej powietrza (dyfuzja pary) i przerywanego zanurzania (przepływ cieczy). Określono właściwości sorpcyjne impregnowanych próbek suszonych w suszarce i próżniowo.
Podczas klimatyzowania próbki świerka pospolitego impregnowanego woskiem, suszone
w suszarce i próżniowo, wykazały tę samą wilgotność, co próbki kontrolne. Impregnowane, wysuszone próżniowo drewno buka osiągnęło wilgotność do 25% niższą
niż próbki kontrolne. Jeszcze większa różnica była widoczna w trakcie badania sorpcji
w zakresie zmian objętości próbek buka suszonych w suszarce i próżniowo.
Słowa kluczowe: buk, świerk pospolity, wosk polietylenowy, sorpcja, ochrona drewna, środki wodoodporne
Srečko Vratuša, Manja Kitek Kuzman, Vojko Kilar
STRUCTURAL PARTICULARS OF GLUED LAMINATED
BEAMS OF VARIABLE HEIGHT1
The first part of the paper presents the main structural characteristics of laminated timber and describes some Eurocode 5 code requirements which can be more
elaborate than for solid timber. The second part of the paper presents a parametric
comparison of two most typical forms of double beams of variable height with levelled or saddled lower edge. The stress conditions were compared for a number of
differently-shaped double-tapered and pitched cambered beams. The results obtained for a refined mesh of finite elements in the SAP2000 computer program were
compared with the results obtained by simplified formulae given in Eurocode 5.
It was demonstrated that, in general, a correctly modelled finite element model
could account for all structural particulars of beams of variable height; while the
main advantage of the finite element approach seems to be the freedom of forms,
shapes, and material characteristics used in the mathematical model.
Keywords: glued laminated timber, double-tapered beams, pitched cambered beams, apex area, radial stress, stress perpendicular to the grain
Introduction
Modern glued laminated structural timber is a product of the most advanced
technologies which include the most recent findings on materials, design and the
theory of structures. Glued laminated timber is manufactured by gluing together
individual pieces of dimension timber under controlled conditions, forming an
interesting, attractive and versatile architectural and structural building material.
Because it is a manufactured product, it is possible to order glulam parts for a wide
variety of applications and/or configurations. Naturally, occurring defects such as
knots, wanes, and checks in larger-sized timber can be controlled or eliminated in
glulam by using laminations that contain only acceptable flaws. The reasons for
Srečko Vratuša, University of Ljubljana, Slovenia
Manja Kitek Kuzman, University of Ljubljana, Slovenia
Vojko Kilar, University of Ljubljana, Slovenia
20
the relatively small use of laminated timber structures in modern architecture and
building practice are hidden not only among structural or architectural drawbacks,
but sometimes also in human nature which still regards wood as temporary, flammable and unworthy of respect structural material [Stungo 2001; Kitek Kuzman
2008; Ratajczak et al. 2006, 2009].
One of the first reported tests of glulam beams of variable height was performed back in mid 1970s. For example, in [Gopu, Goodman 1975] as well as in
[Gutkowski et al. 1982] the results of the first full-scale tests on (double-) tapered
and curved glulam beams were reported; while in [Möhler 1976; Gopu, Goodman
1977; Möhler, Blumer 1978] the first design recommendations and simplified formulae for (double-) tapered and curved glulam beams were proposed. It was soon
realised that for beams with pronounced slopes, the radial stress capacities might
be problematic for practical design of pitched and tapered glued laminated beams
[Gutkowski, Devey, 1984; Buckner, Gupu 1988; Götz 1996; Žagar 2002]. For
a more rational design the use of additional radial reinforcement was first proposed by [Vincent, Gopu 1985] as well as by [Vonroth, Lober 1987]. The possibilities of using an alternative radial reinforcement also were addressed in more recent publications. For instance, the possibilities of using composite materials and
carbon fibre reinforced polymers strips as reinforcement of glued laminated wood
beams were for example examined by [Kasal, Heiduschke 2004] and [Johnsson
et al. 2007] as well as by [Jasieńko et al. 2010]. The use of self-tapping screws to
increase the load carrying capacity of curved beams was investigated by [Jonsson
2005]. One of the first contributions to finite elements analysis of double-tapered
glulam beams can be found in [Kechter, Gutkowski 1984]; while the first computational determination of the radial reinforcement of pitch cambered beams can
be found in [Vonroth, Lober 1987]. A comprehensive bibliographical review of
the finite element methods (FEMs) applied in the analysis of wood products and
structures can be also found in recent paper by [Mackerle 2005].
In the modern sustainability oriented architectural practice the use of various
forms of beams and frames of variable height made of glued laminated wood has
been becoming more and more popular [CNDB 2002; BCIT 2006; APA 2009].
The simplified formulae included in the codes can be used only for simply supported beams with pre-determined shapes. In all other cases the FEM models are widely used by structural engineers; while a number of modern computer programs
facilitate more accurate modelling, analysis and more economical use of materials.
The aim of this paper is to present the appropriateness of modern general
purpose structural analysis FEM computer program (e.g. SAP2000 2008) for the
analysis of glulam beams of variable height. In the first part of the paper some
structural properties of glued laminated timber are briefly presented. In the second
part a parametric study of a series of double beams of variable height with levelled
or saddled lower edge was performed. The main aspects observed were stresses in
the apex area as well as maximal bending stress and its location. The results obta-
Structural particulars of glued laminated beams of variable height
21
ined for a very refined mesh of finite elements in the SAP2000 structural analysis
program were compared with the formulae for simple beams given in EN 1995-11:2004 (Eurocode 5). It was demonstrated that, in general, a cautiously modelled
finite element model, with appropriate grid density and orientation of local axes
in the direction of grains, using the appropriate wood orthotropic material, can account for all structural particulars of beams of variable height. However, the main
advantage of the finite element approach still is the general freedom of forms,
shapes, various grain orientations, and different material characteristics used in
the mathematical model.
Standards and codes for glued laminated timber
The procedures for design, fabrication, quality control and construction of glued laminated beams were standardised and included in the Eurocode standards.
This paper is limited only to technical regulation related to the design of glued
laminated beams. Glued laminated wood facilitates the use of structural beams of
different shapes and forms. Curved members of virtually any practical radius are
possible to obtain simply by forming individual pieces into desired shape prior to
gluing them. Glulam members are available in much longer lengths and sizes than
standard sawn timber. Beside straight beams of constant height, Eurocode 5 (Part
1-1) also includes beams of variable height in three different typical shapes:
a) Single or double-Tapered beams – fig. 1a,
b) Curved beams – fig. 1b,
c) Pitched cambered beams (Saddled beams) – fig. 1c.
Fig. 1. Typical glued laminated beams: (a) double-tapered beam; (b) curved beam
and (c) pitched cambered beam
Rys. 1. Typowe belki z drewna klejonego warstwowo: (a) belka dwutrapezowa; (b) belka
zakrzywiona; (c) belka zakrzywiona o zmiennym przekroju
EN 14080 standard (Timber structures – Glued laminated timber – Requirements) contains various structural requirements for glued timber in detail. For
example, it prescribes the maximum allowable thickness of laminations regarding
22
the humidity of the environment and the radius of curvature for curved elements.
Especially important is EN 1194 standard (Timber structures – Glued laminated
timber – Strength classes and determination of characteristic values). For instance, an attempt at determination of the quality of grown in Poland pine timber has
recently been made by [Noskowiak et al. 2010].
Fig. 2 and 3 present the various strengths for solid timber class C24 (selected
for comparison) and homogenous glued laminated timber classes GL (last 2 digits
denote bending strength in MPa). The values of modulus of elasticity E along
the grain and perpendicular to the grain are presented as well. It can be seen that
bending strengths for solid timber C24 and glulam GL24 are equal, but all other
strengths are greater for glulam timber. The only exception is tension perpendicular to the grain which is equally small for all classes.
Fig. 2. Bending, tensile and compression strengths and modulus of elasticity for solid
timber C24 and glulam timber
Rys. 2. Wytrzymałość na zginanie, rozciąganie i ściskanie oraz moduł elastyczności dla drewna litego C24 i drewna glulam
Fig. 3. Axial (perpendicular to the grain) and shearing strengths, modulus of elasticity for solid timber C24 and glulam timber
Rys. 3. Wytrzymałość osiowa (prostopadła do przebiegu włókien) i na ścinanie oraz moduł
elastyczności dla drewna litego C24 i drewna glulam
23
In the limit state method, the structure or its component (element, cross section) is considered appropriate for use until it exceeds the limit state when the
strength or usability criteria are no longer fulfilled. The expressions that define
different limit criteria include separate partial safety factors for actions and for
the material. The condition for a limit state design of a structure, which requires
that the design value of the effect of actions (Ed) on a component is smaller than
or equal to its design value of the corresponding resistance (Rd), can be written as:
Ed ≤ Rd = R(Xd ad...) or Ed/Rd ≤ 1
(1)
where: Xd is a design value of the material property,
ad is a design value of geometrical data.
Since Eurocode 5 assumes a linear relation between stresses and deformations, the expression (1) can be further simplified and only the maximum values of
design stress caused by actions (σd) is compared with the design values of material
strength (fd). Design values (Xd) are obtained from the characteristic values (Xk)
as follows:
Xd = kmod⋅Xk/γm
(2)
where: kmod is a modification factor taking into account the effect of the duration
of load and moisture content,
γm is a partial factor for the material property.
All these code requirements also were included in our analysis of selected
beams of variable height.
Material and methods
General
The calculation of stresses for elements made of glued laminated timber is usually more complicated than for the elements made of other materials [Götz 1996;
Žagar 2002]. The main reason for it is the variable geometry of the cross sections,
inclinations of element edge regarding the grain direction in laminations and the
curvature of the element axis. For double-tapered beams with varying cross-section, curved and pitched-cambered beams, special stress conditions in the apex
area should be taken into account (fig. 4a, 4b). In addition to normal bending
stresses σm, transversal-radial stresses σt,90, acting in the direction perpendicular to
the longitudinal direction of beams, should also be expected. These radial stresses
are in many cases the crucial parameter that determines the size of the beam in the
apex area, because the design strength in the direction perpendicular to the grain
is much smaller as the strength in the direction of the grain (fig. 2, 3).
24
Fig. 4a. Part of the pitched cambered (saddled) beam – tensile radial stresses in the
apex area in SAP2000
Rys. 4a. Część belki zakrzywionej o zmiennym przekroju (siodłowej) – naprężenia rozciągające poprzeczne w strefie kalenicy – program SAP2000
Fig. 4b. Special stress conditions in the apex area of a pitched-cambered beam. (σm –
bending stresses, σt,90 – radial stresses; tension perpendicular to the grain direction)
Rys. 4b. Specjalne warunki naprężeń w strefie kalenicy belki zakrzywionej o zmiennym przekroju (σm – naprężenia zginające, σt,90 – naprężenia poprzeczne; rozciąganie prostopadłe do
przebiegu włókien)
Various researchers, especially Möhler [1976], Gopu and Goodman [1977],
and Möhler and Blumer [1978], had done elaborate analyses of such beams and
studied the effects of the above-mentioned parameters on the beam stress conditions. They had also proposed some expressions which facilitate a simplified
analytical calculation of such beams, which were later included in many national
codes and standards (also in Eurocode 5 – see Chapter 4.2). In codes, these specific stress conditions are usually considered by different correction factors for the
calculation of bending and radial stresses. The most accurate analyses were done
by solving the differential equation of a wall made of orthotropic material. Several experimental research studies confirmed the results [Gopu, Goodman 1975;
Gutkowski et al. 1982]. Today it is possible to assess more complicated stress
25
conditions of such beams, also by using a finite element computer program (e.g.
SAP2000 or other). In this case, the mathematical model should be prepared with
care in order to take into account adequate numerical accuracy as well as different
material properties in different directions corresponding to actual grain directions
in glulam elements.
Parametric study
This paper presents a comparative analysis of two most typical shape representatives of beams of variable height, i.e. double-tapered beams and pitched-cambered
beams (also called saddled beams). It is assumed that the beams are supported
only by vertical reactions and that the overturning or buckling out of their plane
is prevented [Eilering, Halbensleben 2007]. The geometry data was derived from
a straight beam made of GL28h with a constant rectangular cross section designed
for a given span (16 m) and assumed design uniform load (21 kN/m). According
to Eurocode 5, the height of such a beam according to bending criteria should be
exactly h = 100 cm, if beam’s width is fixed to b = 20 cm. The frontal area of such
a beam amounts to 16 m2 and the volume to 3.20 m3. Seven variants of double-tapered and seven variants of saddled beams (all with 2c = 0.25 and L = 4 m, see
fig. 6b) considered in the study had the same volume as the original straight beam.
For this reason, their basic geometry data (hap, αap and rin – see fig. 6a) was modified individually for each case as shown in table 1. To ease the comparisons, the
individual beams were labelled with one letter (T for tapered and S for saddled)
and the roof slope in percent (= 100⋅tan αap). Because the same wood volume was
used to produce the beams, the slopes of saddled beams were higher as the slopes
of tapered beams. All modified geometry parameters are presented in table 1.
Table 1. Modified geometry data for considered beams
Tabela 1. Zmodyfikowane dane geometryczne dla rozważanych belek
Double-Tapered beams
Pitched cambered beams (Saddled beams)
Belki dwutrapezowe
SLOPE
[%]
Nachylenie
[%]
T-0
T-2.5
T-5.0
T-7.5
T-10.0
T-12.5
T-15.0
Belki zakrzywione o zmiennym przekroju (siodłowe)
hap [cm]
αap [°]
100
110
120
130
140
150
160
0.00
1.43
2.86
4.29
5.71
7.13
8.53
SLOPE [%]
Nachylenie
[%]
hap [cm]
αap [°]
rin [cm]
S-12.5
S-15.0
S-18.75
S-25.0
114.2
117.3
122.2
130.8
S-37.5
149.8
S-50.0
S-62.5
171.0
194.1
7.13
8.53
10.62
14.04
20.56
26.57
32.01
1732
1457
1182
910
643
513
438
26
Mathematical modelling
The glued laminated beams were modelled as orthotropic 4-node final elements
with appropriate orientation of material characteristics in different directions.
Each (symmetric) beam half was divided into 25 elements in height and 100
elements in length (all together 5,000 elements were used for each beam). The
size of each element was roughly 4 by 8 cm with an approximate size ratio 1:2.
The elements used were not equal due to variable geometry, but their local material axes were always oriented in the direction of grain of the actual material in
a glulam member (Direction 1 – parallel to the grain, Direction 2 – perpendicular
to the grain). The glulam was modelled as orthotropic material of different characteristics in two different directions. The modulus of elasticity E amounted to 1260
kN/cm2 for Direction 1 and to 42 kN/cm2 for Direction 2. The corresponding shear
modulus amounted to 78 kN/cm2 for all directions. In tapered beams, Direction
1 was always parallel to global X direction and the modelling was not problematic.
More demanding was the modelling of pitched cambered beam, where Direction
1 local axis was always perpendicular to the radius of curvature of each element.
In this case, there was a need to use cylindrical coordinates to ease the modelling
of the finite elements mesh. The mesh of finite elements used together with the
direction of the local axes for analysed shape variants are presented in fig. 5.
Fig. 5. Orientation of local axes of finite elements in the direction of the grain
in actual glulam member and the finite elements mesh in SAP2000
Rys. 5. Kierunek ustawienia lokalnych osi elementów skończonych zgodny z kierunkiem
przebiegu włókien w prawdziwej części belki glulam oraz siatka elementów skończonych
w programie SAP2000
27
Additionally, such a finite element approach facilitates combination of different wood qualities (e.g. higher wood quality on lower and upper sides of the
beam), as well as the inclusion of various grain orientations, material characteristics, and forms and shapes in the mathematical model.
Results
Stresses in the apex area
Computer analysis of glued laminated beams facilitates calculation of the complete stress distribution for any cross section. This is an advantage over the simplified expressions from the standards, which facilitate only stress calculations
at a certain point where the maximum values are expected. fig. 6 shows selected
results for analysed double-tapered beams (left) and saddled beams (right). Fig.
6a and 6b show the geometry of the analysed beams. The following four figures
show the design bending stresses. Fig. 6c and 6d show the contour lines of the
same bending stresses and fig. 6e and 6f the distribution of normalised bending
stresses over the height of the beams in the apex area. The last four figures show
the design transverse-radial stresses. Fig. 6g and 6h show the contour lines of the
same radial stresses and fig. 6i and 6j the distribution of normalised radial stresses
over the height of the beams in the apex area. Because the beam heights change,
they are presented as relative values in the way that the “zero” coordinate means
the lower edge and 1.0 coordinate the upper edge of the beam. Also, the design
values of stresses were normalised corresponding to their design value of strength,
which is also shown as reference value among the results in fig. 6. The positive
values mean tension and the negative values compression. The design bending
stresses (σm,d) are normalised with design bending strength (fm,d). According to
Eurocode 5, this value is obtained for a reference height amounting to 60 cm for
glued laminated beams. For lower beams the bending strength is slightly higher
(maximum up to 10%). Another important factor that should be considered is the
strength reduction due to bending of the laminates during production. For these
elements reduction of bending strength depends on the ratio between the radius
of curvature and the thickness of laminates. However, these modification factors
did not apply to the selected geometry of beams, and design bending strength for
material GL28 (short-term load duration class, service class 2 (kmod=0.90) and
material safety factor γm=1.25) amounted to fm,d = 2.016 kN/cm2.
Also the design transverse-radial stresses (σt,90,d) were normalised to their
design strength according to Eurocode 5. The initial design tensile strength for
the direction perpendicular to the direction of fibres for selected material GL28h
(kmod=0.90 in γm=1,25) amounted to ft,90,d = 0.032 kN/cm2. This value should be
28
increased due to the effect of stress distribution in the apex area (dashed part of
the beam in fig. 6a). The amplification factor (kdis) amounted to 1.4 for double-tapered and curved beams and to 1.7 for saddled beams. However, the design
tensile strength should be reduced due to the effect of the size (volume) of the
apex area V (Vmax = 2⋅Vb/3, where Vb is total volume of the beam and V0 = 0.01
m3 is the reference volume value). The final value of design tensile strength can
be expressed as:
(3)
The results in the apex area show the characteristic stress distribution for
normal bending and transversal radial stresses, which are consistent with the research results obtained by various authors [Möhler, Blumer 1978; Žagar 2002].
Also, the obtained stress anomaly on the bottom edge in fig. 6j is known from
the method of finite elements (MKE). The correct value is zero, because there is
no load on the lower beam edge. It can be seen from the distribution of stresses
that the numerical results are limited toward the correct zero value on the lower
beam edge.
It can be seen in fig. 6e and 6f that the bending stresses in the apex zone are
not exceeded for any analysed beam variant. With the increase in beam slope, the
bending stresses decrease, but the radial stresses rapidly exceed the design tensile
strength (fig. 6i, 6j). The increase in the apex height, which is the consequence of
changed geometry, only slightly reduces the maximal radial stress. The increase in
radial stresses is not dangerous for doubled tapered beams in the analysed range,
but it seems to be critical for all pitched cambered beams with slopes higher than
approximately 10%. In the cases where the slope exceeds 50%, the actual radial
stress is already almost five times greater than the allowable design strength. The
main problem is that the design tensile strength in the direction perpendicular to
fibre direction is low. In the discussed case, the only solution is to increase dimensions of the beam in the apex area. Therefore, it can be concluded that for a given
span and load, the increase in saddled beam slope or the increase in beam curvature requires an additional increase in beam volume, which is actually unfavourable
from the structural and economic points of view.
Another solution exists for the beams characterised by high transversal-radial
stresses. Special reinforcing devices can be used which prevent splitting of lamellas in radial directions. These can be made of wood, metal [Vonroth, Lober 1987]
or even of fibre reinforced plastic [Kasal, Heiduschke 2004]. Wooden reinforcing
devices are usually made of harder wood plates which can be glued on both sides
of the beam [Jonsson 2005]. Additionally, nails can be used in order to increase
pressure during the gluing process. The metal devices are usually internal steel
screws for wood or ribbed steel bars. Epoxy resin should be poured in pre-drilled
holes before mounting transversal screws.
29
Fig. 6. (a) Double-Tapered beams and (b) Pitched cambered beams (Saddled beams);
(c, d) Contours of the normal – bending stresses; (e, f) Distribution of the normal –
bending stresses over the height of the beam in the apex area; (g, h) Contours of the
transversal – radial stresses; (i, j) Distribution of the transversal – radial stresses
over the height of the beam in the apex area
Rys. 6. (a) Belki dwutrapezowe i (b) belki zakrzywione o zmiennym przekroju (siodłowe);
(c, d) Kontury prostopadłej – naprężenia zginające; (e, f) Rozkład prostopadłej – naprężenia
zginające na wysokości belki w strefie kalenicy; (g, h) Kontury linii poprzecznej – naprężenia poprzeczne; (i, j) Rozkład linii poprzecznej – naprężenia poprzeczne na wysokości belki
w strefie kalenicy
30
Comparison with Eurocode 5
The simplified formulae in Eurocode 5 for calculation of maximal design bending
stresses are based on the assumption of linear correlation between deformations
and stresses. The more complicated stress conditions in the beams with different
shapes are taken into account with correction factors that are used to multiply the
previously-obtained bending stresses. For all types of considered beams an increase of bending stresses in the apex area should be considered. In the apex area,
transverse-radial stresses are usually the most critical. In the simplified calculation approach, they are determined as a percentage of normal stresses depending
on the inclination of the upper edges of the beam and/or on the curvature of the
lamellas. The radial stresses are then compared with design tensile strength in the
direction perpendicular to the wood fibres, corrected with two factors that include
the effect of stress distribution and actual volume of the apex area [Larsen 2001].
Therefore, the actual stress condition is obtained using different correction factors
(ks on the load side and kf on the capacity side). The stress condition for bending
and for radial stresses can be symbolically expressed as:
(4)
The equations for correction factors for different shapes of beams of variable height are given in Eurocode 5 (Chapter 6.4). The applied expressions and their 3D
graphical representations are briefly summarised in Appendix 1.
The comparison between the values obtained by SAP program and the values
obtained by Eurocode 5 using the simplified expressions and correction factors
described above, are presented in fig. 7. It can be seen that the correlation is fairly
good and that the simplified procedure from the Eurocode is on the safe side.
Fig. 7. The comparison of normalised stresses (left bar chart: normal bending stresses; right bar chart: radial stresses) obtained for the apex area of the analysed pitched cambered beams using SAP2000 and Eurocode 5
Rys. 7. Porównanie znormalizowanych naprężeń (lewy wykres: normalne naprężenia zginające; wykres prawy: naprężenia poprzeczne) otrzymane dla strefy kalenicy analizowanych
belek zakrzywionych o zmiennym przekroju przy zastosowaniu programu SAP2000 i kodeksu Eurocode 5
31
Beside the stress conditions in the apex area, another important beam design
parameter is the maximal bending stress which does not necessarily occur in the
apex area, but rather at the location where the ratio between internal bending moment and beam inertia moment reaches its maximal value. According to elastic
beam bending theory (EBT) the design bending stresses σm,d (x) can be simply
determined as the quotient of design bending moment Md (x) and section modulus
W(x) of the rectangular cross section with variable beam height h(x). In double
tapered beams and in straight parts of saddled beams the height change is linear
and it depends on angles αap and d, as well as the height at the support hs. However, in the apex area of saddled beams the height of the beam does not change
linearly anymore and additionally it depends on the length of the curved apex area
c, which, together with angle d, determines the radius of curvature of the lower
beam edge in this area. The h(x) can be most rationally expressed if the coordinate
system’s origin is placed in the middle of the beam. The expressions obtained for
saddled beams are as follows:
- in the apex area where the change of beam height is nonlinear (x < c):
(5a)
- in the “near support” area where the change of beam height is linear
(c ≤ x ≤ L/2):
(5b)
Fig. 8 presents obtained normalised values of bending stresses obtained using
“Elastic Bending Theory (EBT)”. Only one (right) half of the beam is presented.
Note that x/L=0 stands for the middle beam span and x/L=0.5 for the end of the
beam near the support.
Fig. 8. Normalised bending stresses in double tapered (left) and saddled (right) beams
Rys. 8. Znormalizowane naprężenia zginające w belkach dwutrapezowych (z lewej) i w belkach siodłowych (z prawej)
32
It can be seen that the position of maximal stress varies significantly with the
beam slope. When the beam slope is small, the maximal stress can be expected
closer to the mid span and when the slope is more significant, the maximal stress
occurs closer to the support. This holds true for both types of examined beams.
Only for smaller slopes of examined saddled beams the maximum stress have
actually occurred in the curved apex area (x/L < 0.125 or x < c = 2 m – to the left
from the red vertical line in fig. 8).
For saddled beams a comparison of results obtained by EBT theory and program SAP was made as well. In fig. 9 the coordinates of maximal stress and obtained maximal values for different saddled beams are compared. In most cases the
agreement is satisfying. In some cases the position of maximal stress in SAP is
difficult to obtain, because very similar values appear in different finite elements.
However, the maximal values never differ for more than 10%. In the cases with
very high slopes, the simple linear beam theory might have reached its limits. The
whole procedure of calculating maximal stresses using Equations 5a and 5b and
their coordinates for EBT is rather complicated and was processed in Mathematica [Wolfram 2003].
Fig. 9. The comparison of the position of maximal stress in (left) and normalised
values of maximal bending stresses (right) for analysed pitched cambered beams
obtained using SAP2000 and the Elastic Bending Theory (EBT)
Rys. 9. Porównanie umiejscowienia maksymalnego naprężenia w analizowanych belkach
zakrzywionych o zmiennym przekroju (z lewej) i charakteryzujących je znormalizowanych
wartości maksymalnych naprężeń zginających (z prawej) otrzymanych przy zastosowaniu
programu SAP2000 oraz Teorii Zginania Plastycznego (EBT)
In this case the use of SAP demonstrates some significant advantages over
EBT, because it facilitates calculation of the complete stress distribution for any
cross section. However, in this case the maximum stress is obtained for individual
finite elements instead of being obtained for a specific cross section. This is an
advantage over the simplified expressions from the standards which only facilitate
stress calculation at certain points where the maximum values are expected.
33
Discussion and conclusions
This paper demonstrates that structural characteristics and code required methods
for analysis of glued laminated beams are much more elaborate than in the case of
solid timber. The most important difference consists in better controlled mechanical characteristics defined for the reference glulam element height and depending
on numerous parameters such as material quality, loading duration, moisture, usability class, residual stresses, as well as on the element size, the radius of curvature
and the thickness of lamellas.
Even more elaborate is the behaviour of glued laminated beams of variable
height. In many cases, the radial stresses constitute the crucial parameter that determines dimensions of such beams in the apex area, because the design strength
of wood in the direction perpendicular to the grain is always much smaller than
the strength in the direction of the grain. In this analysis, a series of beams of different heights and curvatures was selected and the results obtained by SAP program
and simplified formulae from Eurocode 5 were compared. Beside normal bending
stresses σm, and radial stresses σt,90, in the apex area, maximal bending stresses
and their locations were observed as well. The comparison of the results indicates
that the correlation is fairly good for all examined cases.
From the results obtained for the beams of the same volumes, but of different shapes, it can be concluded that while the slope of the beams increases, the
bending stresses decrease and the radial stresses increase. The increase in radial
stresses was never critical for any of the analysed double-tapered beams (slope
£ 15%); however, for the pitched cambered beams the situation in the apex area
became critical for all slopes greater than approximately 10%. The radial stresses
in those cases considerably exceeded the design tensile strength perpendicular to
fibre direction. The increase in the apex height, which is the consequence of the
changed geometry, only slightly reduces the maximal radial stress. Therefore, for
pitched cambered beams with the slope greater than 10%, the only solution is
to increase the dimensions of the beam in the apex area or to accommodate the
undesirable radial stresses with additional anchors or other measures. The situation could also be improved by adding a tensile element connecting the supports,
which would minimise horizontal displacement and reduce radial stresses in the
apex area. In general, it can be concluded that for a given span and load, the increase in the beam slope is favourable only for tapered beams. For pitched cambered
beams, the increase in the beam slope and curvature over certain value requires an
additional increase in the beam volume, which is actually unfavourable from the
structural and economic points of view.
It was also confirmed that correctly and cautiously prepared finite element
model can describe all particular stress conditions which are important for practical design of glulam beams of variable height. The finite element analysis facilitates calculation of the complete stress distribution for any cross section and any
34
form of a beam or similar frame type structure. Additionally, such a finite element
approach facilitates combination of different wood qualities (e.g. higher wood quality on the lower and upper sides of the beam), as well as the inclusion of various
grain orientations, material characteristics and shapes in the mathematical model.
This is an advantage over the simplified expressions from the standards, which
facilitate only stress calculation at certain points where the maximum values are
expected. To obtain the correct results, however, the mathematical model and finite element mesh should be prepared with great care and adequate precision in
order to take into account satisfying numerical accuracy as well as realistic orthotropic material characteristics in different directions corresponding to the actual
grain directions in tapered pitched cambered or curved glulam members.
References
APA (The Engineered Wood Association) [2009]: http://www.apawood.org/
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CNDB (Centre National pour Developpment du Bois) [2002]: Recherche – production Lamellé Collé. Paris, France
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of glued-laminated timber with intermediate lateral supports. Bautechnic 84 [6]: 397-402
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glulam beams. Journal of the Structural Division – ASCE 108 [10]: 2131-2148
Gutkowski R.M., Dewey G.R. [1984]: Design stress capacities of tapered glulam members.
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Kasal B., Heiduschke A. [2004]: Radial reinforcement of curved glue laminated wood beams
with composite materials. Forest Products Journal 54 [1]: 74-79
Kechter G.E., Gutkowski R.M. [1984]: Double-tapered glulam beams - finite-element analysis. Journal of Structural Engineering 110 [5]: 978-991
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v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Ljubljana
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Larsen H.J. [2001]: Properties affecting reliability design of timber structures. Cost E24 Seminar on Reliability of timber structures, Coimbra: 1-26
Mackerle J. [2005]: Finite element analysis in wood research: a bibliography. Wood Science
and Technology 39: 579-600
Möhler K. [1976]: Zur Berechnung von Brettschichtholz-Konstruktionen. Bauen mit Holz
3: 104-108
Möhler K., Blumer H. [1978]: Brettschichtträger veränderlicher Höhe. Bauen mit Holz
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Noskowiak A., Pajchrowski G., Szumiński G. [2010]: Strength of Polish grown pine (Pinus
sylvestris L.) timber. An attempt of determination of quality of timber for structural use.
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790
Ratajczak E., Szostak A., Bidzińska G. [2006]: Budownictwo podstawowym użytkownikiem materiałów i wyrobów drzewnych. Drewno – Wood 175: 5-24
Ratajczak E. [2009]: Foresight w drzewnictwie - scenariusze rozwoju badań naukowych
w Polsce do 2020 roku. Drewno – Wood 182: 143-145
SAP2000 [2008]: Integrated software for structural analysis and design. User’s manual, version 12. Computers and Structures, Inc. Berkeley
Stungo N. [2001]: Wood: New Directions in Design and Architecture. Chronicle Books, San
Francisco
Vincent T.A., Gopu V.K.A. [1985]: Rational design of radial reinforcement in pitch-cambered
glulam beams. Forest Products Journal 35 [1]: 61-67
Vonroth W., Lober R. [1987]: Computational determination of the radial reinforcement
of symmetrical pitch cambered glulam beams according to Vincent Gopu, regarding DIN1052. Holz als Roh-und Werkstoff 45 [6]: 251-254
Wolfram S. [2003]: The Mathematica Book, Fifth Edition. Wolfram Media, Inc.
Žagar Z. [2002]: Drvene konstrukcije I, II. Pretei, Zagreb
List of standards
PN-EN 1194 [1999] Timber structures – Glued laminated timber – Strength classes and determination of characteristic values. CEN, Brussels
PN-EN 14080 [2005] Timber structures – Glued laminated timber – Requirements. CEN,
Brussels
PN-EN 1995-1-1 [2004] (Eurocode 5) Design of timber structures – Part 1-1: General rules
and rules for buildings. CEN, Brussels
Appendix 1
For beams of variable height, Eurocode 5 requires the fulfilment of the stress condition which can be symbolically expressed as:
(6)
36
where: coefficient ks summarises the product of correction factors on the demand
side,
coefficient kf summarises the product of other correction coefficients,
which should be applied on the capacity side.
Bending stresses
For double-tapered and pitched cambered beams considered in this analysis, the demand side correction coefficient ks equals coefficient kl in Eurocode 5,
which can be calculated as:
(7)
where: h is the maximal height of the beam in the apex area (h º hap),
a is the beam slope,
r = rin + 0.5 hap.
For double-tapered beams, the h/r ratio equals zero and k =k1. The relation
between a, h/r and coefficient k is presented in fig. 10.
Fig. 10. Relation between a, h/r and coefficient k
Rys. 10. Zależność pomiędzy a, h/r i współczynnikiem k
37
The capacity side correction coefficient kf includes the reduction of bending
strength due to beam curvature (factor kr) and the correction due to the element
size (factor kh):
(8)
(9)
where: rin is the internal curvature radius of the lower beam edge,
‘t’ is the thickness of the laminates.
The correction factor kh should be used for all elements loaded with bending
or tension that are lower than 60 cm. In this case, the product of correction coefficients for the capacity side can be expressed as:
(10)
Radial stresses
For double-tapered and pitched cambered beams considered in this analysis, the
demand side correction coefficient ks equals coefficient kp in Eurocode 5 which
can be calculated as:
(11)
For double-tapered beams, the h/r ratio equals zero. The relation between a,
h/r and coefficient kp is presented in fig. 11.
Fig. 11. Relation between a, h/r and coefficient kp
Rys. 11. Zależność pomiędzy a, h/r i współczynnikiem kp
38
The capacity side correction coefficient kf in this case includes the reduction
due to the effect of the size (volume) of the apex area V (Vmax = 2⋅Vb/3, where Vb is
the total volume of the beam and V0 = 0.01 m3 is the reference volume value) and
the amplification factor (kdis = 1.4 for double-tapered and curved beams and 1.7
for saddled beams):
(12)
SPECYFIKA STRUKTURALNA KLEJONYCH WARSTWOWO
BELEK O ZMIENNEJ WYSOKOŚCI
Streszczenie
Nowoczesne klejone warstwowo drewno strukturalne jest produktem wykorzystującym najbardziej zaawansowane technologie, które czerpią z najnowszych odkryć dotyczących materiałów, projektowania i teorii struktur. Drewno klejone warstwowo jest
wytwarzane przez sklejenie poszczególnych elementów drewna wymiarowego w kontrolowanych warunkach, co skutkuje powstaniem interesującego, atrakcyjnego i uniwersalnego materiału budowlanego do zastosowań architektonicznych i strukturalnych.
Celem niniejszego opracowania jest sprawdzenie możliwośći stosowania nowoczesnych programów komputerowych FEM do analizy belek glulam o zmiennej wysokości. W pierwszej części artykułu zaprezentowano najważniejsze właściwości strukturalne drewna klejonego i opisano niektóre wymagania kodeksu Eurocode 5. W drugiej
części artykułu przedstawiono porównanie parametryczne dwóch najbardziej typowych
form belek podwójnych o zmiennej wysokości z wyrównaną lub siodłową krawędzią
dolną. Porównano warunki naprężeń belek dwutrapezowych i zakrzywionych o zmiennym przekroju i różnych kształtach. Obserwowano naprężenie w strefie kalenicy, jak
również maksymalne naprężenie zginające oraz jego lokalizacje. Wyniki uzyskane dla
oczyszczonej siatki elementów skończonych w programie komputerowym SAP2000
porównano z wynikami uzyskanymi przy zastosowaniu uproszczonych formuł podanych w kodeksie Eurocode 5. Udowodniono, że model dla elementów skończonych,
o odpowiedniej gęstości siatki współrzędnych i z lokalnymi osiami ustawionymi w kierunku przebiegu włókien, wykorzystujący odpowiedni materiał drzewny, może wskazywać
wszystkie szczegóły strukturalne belek o zmiennej wysokości. Jednakże, główną zaletą
podejścia opartego na wykorzystaniu elementów skończonych pozostaje ogólna swoboda
wyboru form, kształtów, różnych orientacji włókien i różnych specyfikacji materiałów
zastosowanych w modelu matematycznym.
Słowa kluczowe: drewno klejone warstwowo, belki dwutrapezowe, belki zakrzywione o zmiennym
przekroju, strefa kalenicy, naprężenie poprzeczne
Jānis Iejavs, Uldis Spulle, Vilnis Jakovļevs1
THE COMPARISON OF PROPERTIES OF THREE-LAYER
CELLULAR MATERIAL AND WOOD-BASED PANELS
In recent years a reduced weight cell panel, whose trade mark is Dendrolight, has
gained worldwide recognition thanks to the opening of an experimental factory in
Austria and the start-up of a new industrial factory in Latvia with manufacturing
capacity of 65 thousand m3 cell board material per year. Hitherto the internal layer
of cell panel of cellular wood material type has been produced mainly from softwoods like Norway spruce (Picea abies L.) or Scots pine (Pinus sylvestris L.) covered
with plywood, solid wood, particleboard or other material. The reduced weight
cell panel has many applications in the furniture industry, internal cladding, door
production, the transport manufacturing industry, and possibly in the construction
panel production. The essential goal of the research was to identify possible applications of aspen (Populus tremula L.) wood, which is a common broad-leaved tree
in Latvia, as an alternative material to Norway spruce in the production of reduced
weight cell panel. The aim of the initial research was to investigate some physical
and mechanical properties of aspen cell panel covered with aspen and plywood as
well as to compare these physical and mechanical properties with the properties of
wood-based panels.
The following raw materials were used: finger jointed aspen for internal layer;
finger jointed aspen and three-layer birch plywood for external layer; polyurethane and polyvinylacetate adhesives for internal and external layer gluing. Tests of
obtained aspen panel were carried out in accordance with current test standards
for testing of panel and timber properties. The following panel parameters were determined: moisture content, density, swelling in thickness after 24-hour immersion
in water, tensile strength, three-point bending strength and modulus of elasticity,
and four-point bending strength. A relevant conclusion: panels of cellular wood
material type produced from aspen wood have similar physical and mechanical
properties to such cell panels produced from spruce wood.
Keywords: cellular wood material, aspen, cell panel
Jānis Iejavs, Latvia University of Agriculture, Jelgava, Latvia
Uldis Spulle, Latvia University of Agriculture, Jelgava, Latvia
Vilnis Jakovļevs, Latvia University of Agriculture, Jelgava, Latvia
40
Jānis Iejavs, Uldis Spulle, Vilnis Jakovļevs
Introduction
Hitherto reduced weight cell panels have many non-structural applications. To
add another species to the group of applicable wood species, research on aspen
wood cell panel was carried out. The cell panel internal layer was made of grooved solid aspen wood and two external layers of 3 mm thin solid aspen wood
or of three-layer birch plywood. The structure of the cell panel is shown in fig. 1.
As regards the use, the essential requirements for non-structural cell panel are its
density, thickness swelling, strength, and stiffness properties. The essential goal
of the research was to identify possible applications of aspen (Populus tremula L.)
wood, which is a common broad-leaved tree in Latvia, as an alternative material
to Norway spruce (Picea abies L.) in the production of reduced weight cell panel.
Fig. 1. Structure of aspen cell panel
Rys. 1. Struktura osikowej płyty komórkowej
The aspen cell panels for experimental tests were manufactured in the production unit and laboratory of the Forest and Wood Product Research and Development Institute ltd.
Materials and methods
Raw material
To produce reduced weight aspen wood cell panels, industrially produced aspen
timber with the nominal dimensions of 30×90×1500 mm and volume of 1.5 m3
was obtained. Technical data of the finger jointed aspen wood was as follows: finger length – 10 mm, finger pitch – 3.8 mm, tip gap – 0.6 mm. The average moisture content of the boards was 10 %. Polyvinylacetate adhesive Rakoll PVAC 3 was
used for aspen finger jointing. The finger joints were visible on the flat side of the
board. The cell board slices were covered with material of two types: 3-layer birch
The comparison of properties of three-layer cellular material and wood-based panels
41
plywood of the thickness of 3 mm or a layer of aspen solid wood of the thickness
of 3 mm. Fig. 2 shows a schematic illustration of the manufacturing process of
reduced weight aspen panels in the laboratory.
Fig. 2. Schematic illustration of the manufacturing process of reduced weight aspen
panels
Rys. 2. Schematyczne przedstawienie procesu wywarzania osikowych płyt o obniżonej gęstości
Processing
Before further processing, all aspen boards were conditioned in the standard atmosphere (20±2oC; 65±5%) to reach a constant mass and an average moisture
content of 12%. The cross-section dimensions of 25×91.6 mm were obtained by
planing. After planing, double faced grooves were cut into the flat faces of boards
with the following dimensions of the grooves: depth 21 mm, pitch 6.2 mm, width
3 mm (fig. 3.).
42
Fig. 3. Aspen board with grooves
Rys. 3. Płyta osikowa ze żłobkowaniem
Gluing
Two types of non-structural one-component adhesives, i.e. polyurethane Dana
Pu 2116 (PU) and polyvinyl acetate Danafix 447 (PVA), were used in both face
gluing of grooved boards and slice covering with external layers. The average
amount of adhesive applied in face gluing of the boards was 176 gּm-2 for PVA
glue and 137 gּm-2 for PU adhesive. The average amount of adhesive applied in
slice covering with plywood and aspen was 226 gּm-2 for PVA adhesive and 228
gּm-2 for PU adhesive. Face gluing and slice covering was carried out under the
pressure of 0.2 MPa and at the pressing time of 60 minutes for PVA adhesive and
90 minutes for PU adhesive. After face gluing and conditioning, 34 mm thin cell
board slices were cut for internal layer manufacturing. Before covering all cell
slices were sanded to avoid local indentations. Fig. 4 shows the aspen cell slices
before covering them with plywood or aspen.
Fig. 4. Aspen cell slices for panel internal layer
Rys. 4. Warstwy komórkowe z osiki przeznaczone na warstwę wewnętrzną płyty
43
Panel type
Preparation of the specimens was carried out with the aim of determining their
physical and mechanical properties. Four types of aspen cell panels were produced: type 1 – face gluing and slice covering with PU adhesive, 3 mm thin aspen
wood in external layer; type 2 – face gluing and slice covering with PU adhesive,
3 mm birch plywood in external layer; type 3 – face gluing and slice covering with
PVA adhesive, 3 mm aspen wood in external layer; and type 4 – face gluing and
slice covering with PVA adhesive, 3 mm birch plywood in external layer. At least
10 specimens were tested for each type of panel and each property. In total 280
specimens were tested. Fig. 5 shows reduced weight aspen panels covered with
plywood and aspen wood.
Test methods
After conditioning and before testing, average moisture content was determined
according to LVS EN 322 standard for 20 specimens of each type of aspen panel.
The thickness of the specimen for moisture content test was the same as of the
panel, i.e. 40 mm. Other dimensions were according to the standard. An average
density of the 20 specimens of each panel was determined according to LVS EN
323 standard. For all four types of panels an average swelling in thickness after 24
hour immersion in water was determined for at least 10 specimens according to
LVS EN 317 standard. At least 10 specimens from each panel were used to estimate the gluing quality between the external layer and the cell material according
to LVS EN 319 standard. 3-point bending strength and modulus of elasticity were
evaluated for at least 15 specimens for each type of panel according to LVS EN
310 standard.
Fig. 5. Reduced weight aspen panels covered with aspen and plywood
Rys. 5. Płyty osikowe o obniżonej gęstości pokryte osiką i sklejką
The length of the specimen parallel to the grain of the external layer was 900
mm, thickness 40 mm and width 50 mm. 4-point bending strength according to
point 13 of LVS EN 408 standard was evaluated to compare it with the results of
3-point bending strength. In order to compare the mean values of physical and
44
mechanical properties, basic statistical data processing methods were applied to
determine average, standard deviation (s) and variation coefficient (v).
Results
The results of determination of aspen cell panel physical and mechanical properties are presented in table 1.
Table 1. Physical and mechanical properties of reduced weight aspen panels
Tabela 1. Właściwości fizyczne i mechaniczne płyt osikowych o obniżonej gęstości
Type of panel
Rodzaj płyty
External layer of
aspen +
PU adhesive
Type -1
Property
Właściwość
Zewnętrzna warstwa osika+
klej PU
Typ -1
Moisture content
External layer of
plywood +
PU adhesive
Type-2
Zewnętrzna warstwa sklejka+
klej PU
Typ -2
External layer
External layer of
of aspen +
plywood
PVA
+ PVA adhesive
adhesive
Type-4
Type-3
Zewnętrzna
warstwa osika+
klej PVA
Typ -3
Zewnętrzna warstwa sklejka+
klej PVA
Typ -4
10.4
(0.354; 3)
10.2
(0.376; 4)
11.4
(0.370; 3)
11.0
(0.395; 4)
332
(12.0; 4)
369
(12.5; 3)
317
(12.1; 4)
347
(13.2; 4)
Pęcznienie
1
(0.360; 39)
2
(0.264;16)
2
(0.685; 33)
2
(0.464; 27)
Wytrzymałość na
rozciąganie
0.458
(0.241; 54)
0.860
(0.356; 41)
0.783
(0.253; 32)
0.728
(0.198; 27)
16.2
(3.11; 19)
4270
(190; 4)
19.8
(3.14; 16)
3700
(517; 14)
18.5
(1.68; 9)
4080
(275; 7)
16.6
(2.45; 15)
3300
(129; 4)
12.1
(1.30; 11)
16.2
(1.59; 10)
15.8
(2.09; 13)
14.3
(1.71; 12)
Wilgotność
( s; v, %), %
Density
Gęstość
( s; v, %), kgּm
Swelling in thickness
-3
( s; v, %), %
Tension strength
( s; v, %), Nּmm-2
3-point bending
strength and modulus
of elasticity
Wytrzymałość na
zginanie
3-punktowe i moduł
sprężystości podłużnej
( s; v, %), Nּmm-2
4-point bending
strength
Wytrzymałość na
zginanie
4-punktowe
( s; v, %), Nּmm-2
45
The comparison of some aspen cell board properties with common wood-based panel properties are presented in fig. 6, 7 and 8. Density values are given
in fig. 6.
Fig. 6. Wood-based panel density
Rys. 6. Gęstość płyt drewnopochodnych
The average values of aspen cell panel properties were compared with the
properties of 40 mm thick spruce cell panel covered with 3 mm thin spruce solid
timber (Dendrolight S), 40 mm thick Swiss particleboard V20 (Particleboard),
and 27 mm thick Kronoply OSB 3 oriented strand board (OSB 3). Aspen cell
panels had higher density than spruce cell board, which it can be explained by the
initial difference in density of both species. But all four types of aspen cell panels
had considerably lower density than particleboard and oriented strand board.
The values of swellings in thickness after immersion in water for 24 h are
presented in fig. 7. No significant differences were found in thickness swelling.
After 24 hour immersion in water the thickness swelling was 2% or less for all
four types of panels and it was equal to the thickness swelling of spruce panels
covered with spruce. The acquired results were fivefold lover compared to particleboard and OSB 3. The density and thickness swelling parameters indicated that
cell panels could be used as structural material.
Internal bond properties are presented in fig. 8. It can be seen that tension
strength parallel to the plane of the panel of aspen cell panels was lower than the
spruce cell panel tension strength. But still the results were twofold higher if compared with the values for particleboard or structural oriented strand board.
46
Fig. 7. Wood-based panel swelling in thickness
Rys. 7. Pęcznienie płyt drewnopochodnych
According to this initial research on aspen cell panel, aspen wood can be used as
raw material for cell board production. Moreover, some aspen cell panel properties are comparable with or higher than those of frequently used structural wood-based panels.
Fig. 8 Wood-based panel tensile strength
Rys. 8. Wytrzymałość płyt drewnopochodnych na rozciąganie
47
Conclusions
1. The difference in moisture content after conditioning was 1% on average
when polyurethane adhesive DANA PU 2116 and polyvinyl acetate DANAFIX 447 adhesive were applied in the production of aspen cell board panels.
On comparing the influence of the external layer material on the moisture
content of the panels, the results did not show significant differences between
panels covered with birch plywood and aspen wood.
2. For both adhesives the highest density of the panels (358 kgּm-3 on average)
was achieved when birch plywood was used as the external layer material. Its
density was 19% higher than that of reduced weight spruce panels with spruce
external layer, but 20% lower than the average density of spruce solid timber.
The lowest density (332 kgּm-3) was achieved when aspen wood was used as
the external layer material for panels. Its density was 11% higher than that of
spruce panels, but 30% lower than the average for spruce solid timber.
3. No significant differences were found in thickness swelling. After 24 hour immersion in water it was 2% or less for all four types of panels and it was equal
to the thickness swelling of spruce panels covered with spruce.
4. The tensile strength perpendicular to the plane of the board was lower for
all four types of panels compared with spruce panels covered with spruce
(1.3 Nּmm-2), but for three types of panels (PU/P, PVA/A, and PVA/P) it was
higher compared with spruce panels covered with veneer (0.65 Nּmm-2).
5. The 3-point bending test showed that the highest bending strength and modulus of elasticity occurred for aspen cell panels glued with polyurethane adhesive. The highest bending strength was reached for plywood covered panels
(19.8 Nּmm-2), but the highest modulus of elasticity was obtained for aspen
wood covered panels (4270 Nּmm-2). Other types of aspen cell board were
characterised by significantly lower bending strength and modulus of elasticity.
6. For all four types of aspen panels the lowest 4-point bending strength was
found when compared with reduced weight spruce panels covered with spruce
wood (17.9 Nּmm-2), but all tests showed significantly higher bending strength
when compared to reduced weight spruce panels covered with veneer (5.41
Nּmm-2).
7. According to this research aspen wood can be used for efficient production of
reduced weight cell panels. Therefore, it is necessary to continue this research
in order to define possible applications of the new material, even its use as
a structural material.
48
References
Presentation. [2007]: Internet site Dendrolight. Available at: http://www.dendrolight.lv/data/
doc/12561048082289.pdf [Cited 3 Jan 2009]
Rijsdijk J.F., Laming P. B. [1994]: Physical and Related Properties of 145 Timbers. Kluwer
Academic Publishers, London
Technical data sheet. [2010]: Internet site: http://www.kronospan.ch/por/products/rohspan/
technische_daten [Cited 24 Sept. 2010]
Technical information. [2010]: Internet site Dendrolight – The Solid Wood Panel – light, strong and „green”. Available at: http://www.dendrolight.com/dendro/dendro.nsf/
sysPages/x44D9AAF6FE5F171CC12576C00048B026/$file/Technical%20Information-252002%202010.pdf [Cited 8 Sept. 2010]
List od standards
LVS EN 310 2001. Wood-based panels; determination of modulus of elasticity in bending and
of bending strength. Committee for Standardization, Brussels
LVS EN 317 2000. Particleboards and fiberboards - Determination of swelling in thickness
after immersion in water. Committee for Standardization, Brussels
LVS EN 319 2000. Particleboards and fiberboards - Determination of tensile strength perpendicular to the plane of the board. Committee for Standardization, Brussels
LVS EN 322 1993. Wood-based panels - Determination of moisture content. Committee for
Standardization, Brussels
LVS EN 323 2000. Wood-based panels - Determination of density. Committee for Standardization, Brussels
LVS EN 408 2003. Timber structures - Structural timber and glued laminated timber - Determination of some physical and mechanical properties. Committee for Standardization,
Brussels
PORÓWNANIE WŁAŚCIWOŚCI TRZYWARSTWOWEGO
MATERIAŁU KOMÓRKOWEGO ORAZ PŁYT
DREWNOPOCHODNYCH
Streszczenie
Płyty komórkowe o obniżonej gęstości mają szerokie zastosowanie w przemyśle meblarskim, wyposażeniu wnętrz, produkcji drzwi, środkach transportu. Mogą być również stosowane w wytwarzaniu płyt konstrukcyjnych. Założeniem badań było określenie
przydatności drewna topoli (Populus tremula), rozpowszechnionego na Łotwie, jako substytutu drewna świerku, w produkcji płyt o obniżonej gęstości. W badaniach wykorzystano: drewno topoli na warstwę środkową, trzywarstwową sklejkę brzozową na warstwy
zewnętrzne oraz kleje poliuretanowe i polioctanowinylowe. Zbadano następujące parametry wytworzonych płyt: gęstość, wilgotność, spęcznienie, wytrzymałość na rozciąganie,
49
wytrzymałość na zginanie i moduł sprężystości. W podsumowaniu stwierdzono, iż płyty
komórkowe wytworzone z drewna topoli charakteryzują się podobnymi właściwościami
fizycznymi i mechanicznymi jak płyty komórkowe wytworzone z drewna świerku.
Słowa kluczowe: drzewny materiał komórkowy, topola, płyta komórkowa
Agnieszka Jankowska, Magdalena Szczęsna1
THE STUDY OF COLOUR CHANGES OF CHOSEN
SPECIES OF WOOD FROM SOUTHEAST ASIA CAUSED
BY TRANSPARENT COATINGS AND EXPOSURE TO
SUNLIGHT
In recent years the interest in exotic wood species has been increasing, which was
caused by these species’ specific properties. The aesthetic effect of the material,
especially the colour, is the most important aspect. Unfortunately, wood is susceptible to strong discolouration caused by the coating process or exposure to sunlight. This paper describes the influence of these factors on the colour stability of
Asian teak, merbau and kempas wood species that are mainly used for flooring.
It was proved, using spherical spectrophotometer, that uncoated wood became darker when exposed to the action of varnishes and sunlight. Lacquering, waxing and
shellac lacquering of wood does not protect it against discolouration, but makes the
colour more even on the whole surface.
Keywords: exotic wood, Intsia bijuga (Colebr.) O. Ktze, Koompassia malaccensis
Maing. ex Benth., Tectona grandis L., changes of wood colour, wood
coatings
Introduction
The increasing popularity of exotic wood species has been visible in recent years
(an over twelvefold increase – Kozakiewicz 2006). Floors made of exotic wood
species change their colour due to external factors [Kozakiewicz 2005], especially
due to light and oxygen in the air. This poses serious problems, especially when
the floor is partially covered.
Colour is the reaction of sight to 400-700 nm light which enters the eye and is
projected onto the retina (visible light) [Mielicki 1997]. The colour of wood can
be changed using appropriate technical means such as application of a varnish coating or oil paints, which can completely cover the natural colour of wood, but at
Agnieszka Jankowska, Warsaw University of Life Sciences, Poland
Magdalena Szczęsna, Warsaw University of Life Sciences, Poland
52
Agnieszka Jankowska, Magdalena Szczęsna
the same time provide a protective coating designed to preserve the wood against
external factors. Transparent lacquering increases the natural colour intensiveness, but simultaneously accentuates all defects in pattern and colour.
Despite the exotic wood colour descriptions, the professional literature is limited to the data on colour change, but not obtained by organoleptic tests but using
colorimeter. The aim of this study was to determine the colour change of coated
merbau, kempas and teak wood resulting from exposure to sunlight.
The following three Asian wood species, popular in Poland and often used for
flooring, were selected for tests (nomenclature in accordance with PN-EN
13556:2005 standard): merbau (Intsia bijuga (Colebr.) O. Ktze.), kempas (Koompassia malaccensis Maing. ex Benth.), and teak (Tectona grandis L.). Their detailed descriptions and characteristics are provided by Kozakiewicz and Szkarłat
[2004], and Kozakiewicz [2006, 2008]. Before the tests, samples were planed and
sanded. The radial section of more uniform pattern was selected, rather than the
coarser, tangential section. Moisture content in wood ranged from 8% up to 12%.
Boards were cut into test samples of the following dimensions: 70×70×10 mm.
The samples were grouped (except group A – standard samples, and group B –
uncoated wood samples after solar radiation). In every group surface was finished
with various coatings produced by various manufacturers:
–– in group C with two-component water-based polyurethane lacquer,
–– in group D with one-component polyurethane lacquer,
–– in group E with nitrocellulose lacquer,
–– in group F with polyurethane lacquer,
–– in group G with shellac lacquer,
–– in group H with wax.
The materials were used in line with the producers’ suggestions. Then the
coated samples were placed in a room where they were exposed to direct sunlight
for one year (westward).
The analysis of colour change was based on the international CIE L*a*b*
model. Until the time of exposure to sunlight, the samples were kept in isolation
from it in order to preserve their natural colour. Measurements were taken before
coating, after coating and then after exposure to sunlight.
X-Rite SP-60 spherical spectrophotometer was used for the tests. Colour coordinates (in the space dye) described the colour difference. Colour differences were
calculated according to the following formula:
–– total colour difference:
(1)
The study of colour changes of chosen species of wood from southeast asia caused by transparent...
53
where: ∆L* - lightness difference,
∆a* - red colour difference (a>0),
∆b* - yellow colour difference (b>0).
–– saturation difference:
(2)
–– hue difference:
(3)
The average values were calculated from obtained data (5 measurements per
single sample). For lack of a wood discolouration standard this study is based
on PN-ISO 7724-1:2003, PN-ISO 7724-2:2003, PN-ISO 7724-3:2003 standards
concerning lacquer discolouration.
Results
Obtained results for merbau (Intsia bijuga (Colebr.) O. Ktze.), kempas (Koompassia malaccensis Maing. ex Benth.) and teak (Tectona grandis L.) wood are presented in table 1 and fig. 1-3. On the basis of the detailed analysis of gathered data it
may be concluded that coated exotic wood changes its colour, which is caused by
exposure to sunlight. Lightness values dropped in comparison to control samples
(group A), i.e. the wood became darker. The greatest lightness change of merbau
wood was observed in group E (samples coated with nitrocellulose lacquer), and
the lowest in group C (samples coated with two-component water-based polyurethane lacquer). In the case of kempas wood the greatest lightness change was
found in group G (shellac lacquer), and the smallest in group H containing samples coated with wax. The results of teak wood tests were as follows: the darkest
samples were in group F (polyurethane lacquer coating) and the least darkened in
group B (samples subjected to solar radiation, no painting and no paint coatings).
The analysis of the remaining two colour parameters showed that the saturation and hue of the exotic wood changed due to long exposure to sunlight. Colour
saturation (C*) of merbau and teak wood became stronger in all studied groups. In
the case of kempas wood chrome coating increased the paint systems of groups C,
D, E, and H, and decreased in groups B, F, and G (the samples’ surfaces became
pale).
It was observed that the average value of hue (H*) decreased for tested wood
species, which means that their colour changed. Based on this parameter it can be
determined (not organoleptic) that the similar to orange-red colour of the samples
of kempas wood and merbau wood became more similar to red-brown, while the
colour of kempas wood samples was darker.
54
Table 1. The comparison of the colour parameters of wood species from Southeast
Asia caused by varnishing coatings and exposure to sunlight
Tabela 1. Zestawienie parametrów barwy drewna pochodzącego z Azji Południowo-Wschodniej pod wpływem powłok lakierniczych i ekspozycji na działanie światła słonecznego
KEMPAS
(Koompassia malaccensis
Maing. ex Benth.)
MERBAU
(Intsia bijuga (Colebr.) O. Ktze.)
Wood
species
Gatunek
drewna
Group
Grupa
Colour parameters
Cecha barwy drewna
Lightness (L*)
Wartość jasności
L*min
uncoated
wood
drewno bez
powłoki
Saturation (C*)
Wartość chromy
Hue (H*)
Wartość odcienia
L*av./
C*av./
H*av./
L*max C*min
C*max H*min
H*max
śr
śr
śr
A 39.82 44.47 50.10 20.53 22.45 25.43 52.77 55.35 58.94
B 42.09 42.98 44.39 21.73 22.89 24.09 54.70 55.11 55.55
C 41.54
coated wood D 40.62
after exposure to sunlight E 40.09
drewno
F 41.20
43.02 44.89 24.74 26.44 27.52 53.42 54.93 56.25
41.77 42.70 23.15 24.86 26.23 52.45 53.30 54.37
40.38 40.85 24.66 25.11 25.90 48.82 49.19 49.82
41.88 42.58 23.68 24.06 24.58 48.71 49.36 50.18
z powłoką po
naświetlaniu G 41.11 41.70 42.50 25.95 27.65 29.01
49.83 50.59 51.51
H 41.39 42.53 44.22 25.67 26.44 28.35 49.35 50.38 51.33
uncoated
wood
drewno bez
powłoki
A 47.65 51.93 54.20 23.28 26.92 28.94 52.82 54.52 55.99
B 39.41 40.81 41.83 21.95 22.94 23.62 48.41 48.83 49.35
C 39.36
coated wood D 40.83
after exposure to sunlight E 42.10
drewno
F 37.83
41.02 41.77 25.85 27.62 28.73 44.83 47.12 47.90
42.14 43.05 25.33 27.45 29.35 47.14 48.69 48.71
43.28 45.04 27.89 28.78 30.62 48.69 50.00 52.04
38.83 39.99 22.33 23.96 24.92 40.21 41.28 42.07
z powłoką po
naświetlaniu G 36.36 36.84 37.72 23.24 24.84 26.40
41.72 42.73 44.23
H 44.36 44.77 45.65 26.82 27.86 28.58 50.28 50.81 51.74
TEAK
(Tectona grandis L.)
uncoated
wood
drewno bez
powłoki
A 45.57 54.37 60.89 23.18 26.71 31.50 63.11 67.52 69.32
B 52.92 53.48 53.51 33.82 34.14 34.86 64.46 64.66 64.89
C 50.32 51.31 53.20 30.72 31.23 31.78 62.56 63.72 65.13
coated wood D 52.49 53.93 55.25 29.07 30.94 31.81 64.82 66.02 67.30
after exposure to sunlight E 42.12 46.57 49.94 26.99 30.62 33.10 58.68 61.26 63.24
drewno
F 41.48 44.42 47.52 24.33 27.02 31.14 56.27 58.10 60.59
z powłoką po
naświetlaniu G 47.39 47.80 48.35 33.14 34.45 35.32
60.60 61.44 62.12
H 41.88 45.58 47.69 24.33 28.14 30.70 57.67 60.89 63.75
55
Fig. 1. The appearance of coated merbau wood samples (Intsia bijuga (Colebr.)
O. Ktze.) after exposure to sunlight
Rys. 1. Wygląd próbek drewna merbau (Intsia bijuga (Colebr.) O. Ktze.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
Fig. 2. The appearance of coated kempas wood samples (Koompassia malaccensis
Maing. ex Benth.) after exposure to sunlight
Rys. 2. Wygląd próbek drewna kempas (Koompassia malaccensis Maing. ex Benth.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
Fig. 3. The appearance of coated teak wood samples (Tectona grandis L.) after exposure to sunlight
Rys. 3. Wygląd próbek drewna tikowego (Tectona grandis L.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
56
The biggest differences in this parameter were observed for a merbau wood sample
from group C (two-component paint, water-based) and for kempas wood samples
from group F (polyurethane lacquer). In the case of teak wood, it was observed
that samples of a colour similar to yellow got a bit darker shade of yellow, and the
biggest difference in hue was recorded for samples from group E (nitrocellulose
lacquer).
For comparison of different coatings, a total colour difference criterion
(fig. 4-6) and colour stabilisation was set. The scope of wood colour changes was
set on the basis of a nine-step scale [Mielicki 1997] given in table 2.
Fig. 4. The comparison of total colour difference of coated merbau wood (Intsia bijuga (Colebr.) O. Ktze.) caused by exposure to sunlight
Rys. 4. Zestawienie całkowitej różnicy barwy drewna merbau (Intsia bijuga (Colebr.)
O. Ktze.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
Fig. 5. The comparison of total colour difference of coated kempas wood (Koompassia
malaccensis Maing. ex Benth.) caused by exposure to sunlight
Rys. 5. Zestawienie całkowitej różnicy barwy drewna kempas (Koompassia malaccensis Maing. ex Benth.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
57
Fig. 6. The comparison of total colour difference of coated teak wood (Tectona grandis L.) caused by exposure to sunlight
Rys. 6. Zestawienie całkowitej różnicy barwy drewna tikowego (Tectona grandis L.) pokrytego powłokami po ekspozycji na działanie światła słonecznego
Table 2. Colour stability [Mielicki 1997]
Tabela 2. Stopnie trwałości barwy [Mielicki 1997]
Colour difference
Różnica barwy
∆E
Colour stability
Stopień trwałości
barwy
0±
0.2
0.8 ±
0.2
1.7 ±
0.3
2.5 ±
0.35
3.4 ±
0.4
4.8 ±
0.5
6.8 ±
0.6
9.6 ±
0.7
13.6 ±
1.0
5
4-5
4
3-4
3
2-3
2
1-2
1
On the basis of the classification presented in table 2, it can be said that there
was no correlation between tested wood species (the colour of each species covered with the same painting and varnish coatings reacted differently to exposure
to natural sunlight). In the case of merbau wood the highest degree of colour
stability was found in the group of samples subjected to solar radiation, but not
coated with lacquer painting and coatings (group B). The most durable colour of
kempas wood samples was found in the group of wax-coated samples (group H),
and in the case of teak wood it was observed in the group of samples coated with
one-component polyurethane varnish (group D).
Conclusions
The tests run on three popular wood species from Southeast Asia, i.e. merbau,
kempas and teak wood, consisting in the evaluation of colour changes of wood
caused by different transparent coatings and exposure to sunlight, allow the following conclusions:
1. transparent coatings (varnishes, wax, and shellac) and exposure to sunlight
caused changes in colours of wood surface,
58
2. changes in colour were different in the three tested kinds of wood; the scope
of changes depended on the finishing coating applied,
3. covering of the wood samples’ surface with varnishes, waxes, and shellac,
and then subjecting them to sunlight resulted in darker colour of the samples,
4. generally application of varnish, wax and shellac did not protect wood from
changes of colour; however it made the colour more even on the entire wood
surface.
References
Kozakiewicz P., Szkarłat D. [2004]: Tik (Tectona grandis Linn. f) – drewno egzotyczne
z południowo-wschodniej Azji. Przemysł Drzewny 2: 27-30
Kozakiewicz P. [2006]: Merbau (Intsia sp.) – drewno egzotyczne z Azji i Oceanii. Przemysł
Drzewny 9: 21-24
Kozakiewicz P. [2006]: Kempas (Koompassia malaccensis Maing) – drewno egzotyczne
z południowowschodniej Azji. Przemysł Drzewny 4: 33-36
Mielicki J. [1997]: Zarys wiadomości o barwie. Wyd. Fundacja Rozwoju Polskiej Kolorystyki, Łódź
List of standards
PN-EN 13556:2005 Drewno okrągłe i tarcica. Terminologia stosowana w handlu drewnem
w Europie
PN-ISO 7724-1:2003 Farby i lakiery – Kolorymetria – Część 1: Podstawy
PN-ISO 7724-2:2003 Farby i lakiery – Kolorymetria – Część 2: Pomiar barwy
PN-ISO 7724-3:2003 Farby i lakiery – Kolorymetria – Część 3: Obliczanie różnic barwy
BADANIE ZMIAN BARWY WYBRANYCH GATUNKÓW
DREWNA Z AZJI POŁUDNIOWO-WSCHODNIEJ
SPOWODOWANYCH TRANSPARENTNYMI POWŁOKAMI
I ODDZIAŁYWANIEM ŚWIATŁA SŁONECZNEGO
Streszczenie
W ostatnich latach widoczna jest rosnąca popularność drewna egzotycznego na rynku
europejskim. Podłogi wykonane z drewna egzotycznego zmieniają swoją barwę pod
wpływem czynników zewnętrznych. W opisach barwy drewna egzotycznego w literaturze fachowej brak danych, pozyskanych nie organoleptycznie, lecz za pomocą kolorymetrów fizycznych. Celem niniejszej pracy było zbadanie, przy użyciu spektrofotometru
sferycznego, zmian barwy wybranych gatunków drewna z Azji Południowo-Wschodniej
(tik, merbau, kempas) z naniesionymi transparentnymi powłokami pod wpływem działa-
59
nia światła słonecznego. Analizę zmiany barwy wykonano na podstawie matematycznego
modelu przestrzeni barw CIE L*a*b*, opracowanego przez Międzynarodową Komisję
Oświetleniową, uwzględniającego zalecenia zawarte w normie PN-ISO 7724-3:2003.
Wyniki przeprowadzonych badań pozwalają stwierdzić, że transparentne powłoki
(lakiery, wosk, politura) i ekspozycja na działanie światła słonecznego powodują zmiany barwy drewna. Zmiany barwne mają zróżnicowany charakter dla badanych gatunków
drewna, a wielkość zmian jest zależna od zastosowanego środka uszlachetniającego.
Większą zmienność barwy wykazuje drewno, które zostało pokryte powłokami niż drewno niczym niezabezpieczone. Lakierowanie, woskowanie i politurowanie drewna generalnie nie zabezpiecza go przed zmianami barwy, jednak wyrównuje jego kolorystykę (barwa
drewna jest wyrównana na całej powierzchni).
Słowa kluczowe: drewno egzotyczne, Intsia bijuga (Colebr.) O. Ktze, Koompassia malaccensis
Maing. ex Benth., Tectona grandis L., zmiany barwy drewna
Jarosław Banecki1
COMPARATIVE STUDIES OF FURNITURE LACQUER
COATINGS’ RESISTANCE TO LINEAR SCRATCHING ACC.
TO THE METHOD DESCRIBED IN TS 15186:2005
The article presents results of comparative studies of the resistance of lacquered
furniture surfaces to linear scratching. The studies were performed in cooperation
with industrial laboratories and using a new method for evaluation of this functional property of the surface. The effect of the studies performed was the assessment
of reproducibility and repeatability of the test final results for tested set of furniture
surfaces. The results of the studies also served to assess the differentiation of furniture surfaces in terms of their resistance to scratching.
Keywords: furniture surface, surface resistance to linear scratching, reproducibility of the scratch test final result, repeatability of the scratch test final
result, differentiation of furniture surfaces
Introduction
Resistance to scratching is a functional property of furniture surfaces that is important in both furniture production processes and furniture service life. This
property together with other essential features of furniture surface coatings, such
as abrasibility and impact value, decides the coating mechanical resistance, especially by reflecting its hardness. Hence, the resistance to scratching is also called
the scratch hardness. The wood-based substrate also influences furniture surface
resistance to scratching, but this influence is significant only when the coating
applied on this substrate is thin, i.e. of the thickness of less than 50 μm, and
the substrate is characterised by considerable heterogeneity. Testing of coating’s
resistance to scratching is a subject considered in theoretical approach concerning complex phenomena connected with the appearance of scratches on coatings
made of various lacquer products [Shen 2006a, b], as well as in practical approach
concerning usefulness and credibility of defined methods for testing this surface
property [Emmler, Nothelfer-Richter 2005; Krzoska-Adamczak 2001].
Jarosław Banecki, Wood Technology Institute, Poznan, Poland
62
Jarosław Banecki
For many years the Clemen method, described in PN-65/C-81527, was the
procedure used for testing resistance of furniture surfaces to scratching. In that
method a steel graver with the sintered carbide tip of defined geometry serves as
the scratching tool. That method was intended for testing lacquer coatings cured
on standardised steel plates. Therefore, if used for testing coatings produced on
porous wood or wood-based substrates, the impossibility of unambiguous determination of minimum tip load, which causes appearance of a continuous visible
scratch without damaging the substrate's structure, often was pointed out. Another method for assessment of coating resistance to scratching that was used in
Poland was the procedure according to PN-88/F-06100-11 which employed sapphire gramophone needle as the scratching tool. That method was used to evaluate hardness of coatings on furniture surfaces by determining the tip load causing
appearance of a scratch of the width of 50 μm [Paprzycki, Serafinowska 1990].
Another way of evaluation of lacquer coating resistance to scratching is the method described in BN-78/6110-03 which employs a set of graphite pencils by “Koh
and Noor” in which there are pencils of 17 standardised graphite hardness values.
Nominally this procedure is used for determination of so-called pencil hardness of
lacquer coatings cured on a steel or glass plate. The scratch test according to Taber
is an example of another, less known, method for determination of lacquer coating resistance to scratching. This test is used in comparative studies of functional
resistance of coatings produced from various products [Lange et al. 1997; Poitoux
2006]. A separate group consists of workshop methods that are applied in current
rough assessment of coating resistance to scratching. Amongst these methods is
the procedure using 318 DBGM tool according to Erichsen or so-called “coin
test” performed using, for instance, the Hamberger Planer device (coin). These
test methods are not standardised.
In the last few decades tests of furniture surface resistance to scratching,
depending on the type of tested furniture finish and specification of requirements [Krzoska-Adamczak 1996,1999], have been carried out according to
methods described in the following standards: EN 438-2:1991, EN 438-2:2005,
ISO 1518:1992, and SIS 839117:1973 [Krzoska-Adamczak 2001]. Except for
the procedure according to EN 438-2:2005, the principles of methods described
in the other above-mentioned standards are similar, i.e. all the methods look
for the least load of the tip of defined geometry which will produce on tested
furniture surface a visible or measurable trace of a scratch of defined continuity or width. The diversification of basic elements of the above-mentioned test
methods caused a lack of possibility of unambiguous comparison of the final
results of tests for resistance to scratching carried out using these methods. This
fact was an important reason for taking up methodological research on development of a new method for assessment of surface resistance to scratching which
would encompass a wider range of furniture finishes. An original method of
testing furniture surface resistance to scratching was developed under the Euro-
Comparative studies of furniture lacquer coatings’ resistance to linear scratching ...
63
pean research project entitled “Test methods on wear resistance and long-term
stability of furniture surfaces” (FUNFACE) [Banecki et al. 2004; Emmler et
al. 2004, 2005; Krzoska-Adamczak, Nowaczyk 2004a]. The said test procedure
was validated by carrying out two series of inter-laboratory comparative tests
in co-operation with the research laboratories which participated in FUNFACE
project. The conclusions from those comparisons were used to appropriately
modify the preliminary version of the method, and then to draw up a draft of a
technical standard containing the modified test procedure [Krzoska-Adamczak,
Nowaczyk 2004b].
The developed test method was granted the status of technical requirements
and is described in technical standard TS 15186:2005 as method A. The method
is characterised by such things as: optimised geometry of the scratching diamond
tip, new definition of the scratch trace which is independent of the type of furniture surface finish (all finishes except for laminate coatings), and an objective
way of the scratch assessment based on the scratch width measurement. The results of successive comparative studies of the developed method and procedures
according to EN 438-2:1991 and SIS 839117:1973, carried out in two series of
tests on 11 different furniture surfaces in the laboratory of the Wood Technology
Institute (ITD) in Poznan, allowed a statement that test procedures according
to TS 15186 (method A) and SIS 839117 to a large extent differentiate furniture surfaces finished with various materials (clear lacquers, enamels, foils, short
cycle laminates) [Banecki, Krzoska-Adamczak 2007]; however, the procedures
demonstrate a bit worse repeatability of the test final result (90%) compared with
the method according to EN 438-2:1991 (100%). Moreover, a strong linear correlation between method A described in TS 15186 and the procedure set forth
in SIS 839117 was proved. The results of the analyses allowed a conclusion
that method A described in TS 15186 can replace the procedure according to
SIS 839117:1973. As a result of successive standardisation activities carried out
in the framework of CEN/TC207/WG7, method A described in the above-mentioned technical standard, after taking into account only some minor corrections,
was included in a draft of EN 15186:2010. Currently, this draft is being at the
stage of public survey.
Within the framework of the programme of inter-laboratory comparative studies, the method for determination of surface resistance to scratching according to
TS 15186 was presented to selected producers of lacquer products and furniture
operating in Poland. Additionally, the reproducibility and repeatability of the final
assessments of resistance to scratching, obtained for six different furniture surfaces in two test sessions, at each participating labolatory (5 entities) were evaluated.
The article presents the results of those studies.
The aims of the studies were:
–– to determine reproducibility and repeatability of the results of tests of furniture surface resistance to linear scratching carried out in industrial laboratories
64
Jarosław Banecki
and in the ITD laboratory using test method A described in technical standard
TS 15186,
–– to determine the ability of the test method applied to differentiate furniture
surfaces.
The programme of the studies comprised:
–– preparation of samples of board furniture elements (6 types) of surfaces finished in various ways, i.e.:
–– with lacquer coating made of pigmented solvent-based 2K products, also
of high solids type, and of UV-cured products,
–– with lacquer coating made of thermosetting powder paint,
–– with tinted lacquer coating made of transparent 1K waterborne product,
–– thickness measurements of lacquer coatings on the samples prepared for tests,
–– acquaintance of selected industrial laboratories with the new test method during the informational and training meeting, organised by the ITD in Poznan,
whose agenda contained such items as:
–– presenting description of the test method to the participants; the description was prepared in the ITD based on TS 15186 (method A),
–– carrying out by the qualified staff of the ITD laboratory demonstrative
tests of resistance to scratching using the said test procedure,
–– common assessment of resistance to scratching of furniture surfaces subjected to demonstrative scratch tests,
–– carrying out inter-laboratory tests by the participants, i.e. four industrial laboratories and the ITD laboratory were to carry out two series of tests of resistance to scratching of each of 6 furniture surfaces using the above-mentioned
test method,
–– performing an analysis of the test results as regards selected features of the
test method applied (reproducibility and repeatability of the test final results
furniture surfaces differentiation).
Test materials
Board furniture elements of surfaces finished in various ways, 6 different types
of surface finish, were used in studies. Those elements were: MDFs of different
thicknesses, HDF, wet-pressed fibreboard, and particleboard covered with beech
veneer; the boards were finished with pigmented or clear lacquer coatings. The
board furniture elements used in comparative studies were produced in industrial
conditions. Characteristics of the substrate material and its surface finish for every
board furniture element is given in table 1.
65
Table 1. Characteristics of furniture panels applied in comparative studies
Tabela 1.Charakterystyka płytowych elementów meblowych zastosowanych w badaniach porównawczych
Code of furniture surface
Kod
powierzchni
meblowej
PM – 1
PM – 2
PM – 3
PM – 4
PM – 5
PM – 6
1)
1)
Substrate material
Materiał podłożowy
MDF (18 mm)
Płyta MDF o grubości 18 mm
Wet-pressed fibreboard (3 mm)
Mokro formowana
płyta pilśniowa o
grubości 3 mm
MDF (16 mm)
Type of surface finish
Typ wykończenia powierzchni
Average
thickness of
lacquer coating1) [μm]
Średnia grubość pokrycia
lakierowego1)
[μm]
3-layer coating made of solvent-based
pigmented 2K PUR lacquers of High Solids
type (HS)
Pokrycie lakierowe 3 – warstwowe wytworzone z rozpuszczalnikowych poliuretanowych
wyrobów kryjących (2K) typu high solids
Pigmented lacquer coating made of UVcured products of HS type
Pokrycie lakierowe wytworzone z emalii typu
high solids utwardzonej promieniowaniem UV
3-layer coating made of solvent-based pigmented 2K Ac lacquer in base and top layers
Płyta MDF o grubo- Pokrycie lakierowe 3 – warstwowe wytworzości 16 mm
ne z akrylowej rozpuszczalnikowej emalii (2K)
w warstwach podkładowej i nawierzchniowych
HDF (3 mm)
Płyta HDF o grubości 3 mm
MDF (19 mm)
Płyta MDF o grubości 19 mm
Particleboard
(18 mm) covered
with beech veneer
(0.5 mm) on both
sides
71
21
230
5-layer coating made of UV-cured Ac putties, base Ac lacquers and top Ac enamel
Pokrycie lakierowe 5 – warstwowe wytworzone z użyciem szpachlówek akrylowych, wyrobów podkładowych i nawierzchniowej emalii
akrylowej utwardzonych promieniowaniem UV
Structured coating made of low bake thermosetting powder paint
Powłoka strukturyzowana wytworzona z użyciem niskotemperaturowej termoutwardzalnej
farby proszkowej
3-layer coating made of water-based stain
and waterborne 1K Ac transparent lacquer
in base and top layer
Pokrycie lakierowe 3 – warstwowe wytworzoPłyta wiórowa o
ne z użyciem bejcy wodnej, warstwy podkładogrubości 18 mm
wej i warstwy nawierzchniowej z akrylowego
oklejona dwustronnie
wyrobu wodorozcieńczalnego (1K)
fornirem bukowym
(0,5 mm)
Presented values were calculated on the basis of results of thickness measurements
Podane wartości obliczono na podstawie wyników 10 jednostkowych pomiarów grubości
39
286
91
66
Jarosław Banecki
Samples of board furniture elements intended for comparative studies were
prepared in the ITD in Poznan. Preparation of the samples included:
–– cutting to size of test samples of the dimensions of (10×10×thickness) cm,
–– marking cut-to-size samples with a description code containing information
on: participant of studies, furniture surface, test series, and test sample number,
–– seasoning and conditioning of test samples in the period of 4 weeks preceding performance of scratching resistance tests in a given laboratory; samples
were conditioned for 7 days in a Thermocold KK-08 climatic chamber under
normal conditions: temperature of 23±2ºC and relative humidity of 50±5%,
–– after the 3-week period of seasoning and the 7-day conditioning, sets of test samples were put into plastic packaging (polyethylene foil) protecting the samples’
surfaces from possible scratching during transport to target industrial laboratory.
The thickness of lacquer coatings of furniture elements for testing was measured by the ultrasonic method. The thickness measurement was done using
a QuintSonic PRO ultrasonic thickness gauge by Elektro-Physik GmbH. The final
result of measurements for a given surface finish variant was the arithmetic mean
value from ten thickness measurements taken at randomly selected points of tested furniture surfaces (table 1).
Test methods
To acquaint industrial laboratories with the test method intended for use in comparative studies, the following forms of transfer were applied:
–– passing on the information on the developed test procedure in the form of
Power Point presentation together with commentary during the informational
and training meeting organised in the ITD,
–– demonstration of making a linear scratch on a furniture surface and taking measurements of the widths of scratches produced on the demonstrative surface,
–– demonstration of apparatuses used in the ITD laboratory for making surface
scratch and taking measurements of the width of scratches produced on the
surface.
The following industrial partners participated in the inter-laboratory comparative studies: Becker Acroma Polska Sp. z o.o., Czerska Fabryka Mebli KLOSE
Sp. z o.o., Fabryka Mebli BALMA S.A., and Fabryka Mebli FORTE S.A. Division in Suwałki. The fifth participant of the studies was the Wood Technology
Institute (ITD) in Poznan. Individual laboratories taking part in the studies were
randomly marked with the codes: LAB1 – LAB5.
Tests of resistance of described furniture surfaces to linear scratching were
performed by each of the above-mentioned participant at the time suitable for them
within the period from August to November 2008. All participants of comparative
studies carried out 2 series of surface scratching resistance tests of each of the
67
6 furniture surfaces using method A described in TS 15186. A departure from that
methodical description, which occurred during execution of tests in all participating laboratories, was taking measurements of the width of scratches produced on
the tested surfaces only by 2 observers using the same optical measuring device.
The scratch width measurement was taken in its middle part.
To carry out the scratch tests and assess scratches produced on tested furniture
surfaces, particular laboratories applied the following testing and measuring apparatuses as well as auxiliary materials:
–– device for surface linear scratching – Scratch Hardness Tester model 239/II
by Erichsen GmbH & Co KG – equipped with electric drive allowing tip's
movement with the velocity of 20 ± 10 mm/s in the range of its load 1÷20 N,
–– diamond scratching tip of cone geometry: radius of tip's rounded part
R = 0.30±0.01 mm, cone angle α = 60±1˚,
–– measuring stereoscopic microscope – MOTIC model SMZ-140/143 – of the
magnification range of 10÷40´, equipped with digital camera MOTICAM
2000, co-operating with the computer programme Motic Images Plus in the
scope of its measuring function, allowing scratch width measurement with the
uncertainty of ± 0.01 mm,
–– workshop measuring microscope by PZO of the magnification of 20´ allowing
scratch width measurement with the uncertainty of ± 0.01 mm,
–– graphite of HB hardness and water-soluble ink (black) as materials for contrasting the route of scratch edges on tested furniture surfaces.
The reproducibility of the test final result in laboratories participating in the
comparison was assessed for a given test object, i.e. for a defined furniture surface and within a given test series, using the value of variation coefficient of
scratch test final result. Taking into account values of variation coefficient of
scratch test final result calculated for individual furniture surfaces, mean values
of that coefficient were determined for each of two test series. Those values
characterised average level of variability of the final results in 5 laboratories
participating in the comparison, corresponding with the set of furniture surfaces
used in the tests.
The following criterion was adopted for the need of assessment of repeatability of the final result of test of furniture surface resistance to scratching:
“The final result of scratch resistance test is considered repeatable for a given
furniture surface if final results of its resistance obtained in the same laboratory in two consecutive test series do not differ between one another by more
than 1 N” [Banecki, Krzoska-Adamczak 2007; Krzoska-Adamczak, Nowaczyk
2004b]. Applying the hereinbefore described repeatability criterion to each laboratory participating in the comparison, the percentage share of furniture surfaces
for which the criterion was fulfilled was determined. The calculated percentage share was considered the measure of repeatability of the test final result in
a given laboratory for the set of furniture surfaces used.
68
Jarosław Banecki
For the assessment of differentiation of furniture surfaces by the test method
applied, it was assumed in the carried out tests that the measure of that differentiation was the parameter defined by equation (1):
(1)
where: D – degree of furniture surfaces differentiation as regards their resistance
to scratching determined by using the test method applied, %,
Max ÷ maximum resistance to scratching which was observed amongst
furniture surfaces subjected to tests, N,
Min. ÷ minimum resistance to scratching which was observed amongst
furniture surfaces subjected to tests, N,
ΔL – difference between maximum and minimum load of the scratching
tip applied in the test method used – it was the interval of the tip loads in
the method applied, N.
The value of the degree of furniture surfaces differentiation as regards their
resistance to scratching was determined for every laboratory participating in the
comparison, separately for the first (I) and the second (II) test series. The divergence in values of that parameter amongst individual laboratories were evaluated
by determination of the value of variation coefficient of the degree of surfaces
differentiation in test series I and test series II.
Discussion of test results
Fig. 1-6 present values of final results of resistance to scratching of furniture surfaces PM-1 to PM-6, respectively, in relation to the participant of comparative
studies and the test series. The values of those results indicate high resistance to
scratching of furniture surfaces PM-3 and PM-1 finished with lacquer coatings
of chemo-hardened solvent-based products based on acrylic or urethane binders.
Furniture surface PM-5, finished with structured coating of thermosetting powder
paint, demonstrated comparable resistance to scratching. In the case of those three
furniture surfaces, the influence of the substrate material on their scratch resistance was insignificant due to the thicknesses of respective lacquer coatings (over 50
μm – table 1) and the fact that the substrate in all above-mentioned furniture surfaces was made of MDF, i.e. of a material of high homogeneity of surface and stable
hardness. A different situation occurred in the case of furniture surfaces PM-2
and PM-4 finished with lacquer coatings of UV-cured acrylic products. Due to
low thickness of those lacquer coatings (less than 50 μm), it should be recognised
that the type of the substrate material had a bearing on scratch resistance of those
furniture surfaces. Average values of final results of scratch resistance calculated
for those furniture surfaces indicate clear difference in their resistance values , i.e.
69
7.0 N for surface PM-2 (fig. 2) and 11.0 N for surface PM4 (fig. 4). The observed
difference in scratch resistance values for both considered furniture surfaces may
result from differentiation of hardness values of wet-pressed fibreboard and HDF,
which were the substrates for those surfaces, and it may be an effect of the difference in average thicknesses of both lacquer coatings (table 1).
Fig. 1. Final assessment of PM-1 surface resistance to scratching depending on the
participant of comparative tests and the test series
Rys.1. Końcowy wynik badania odporności na zarysowanie powierzchni meblowej PM-1
w zależności od wykonawcy badania i serii badawczej
70
Jarosław Banecki
The last of tested furniture surfaces marked with the code PM-6 demonstrated
the lowest scratch resistance at the level of 6.0 N (fig. 6). This test result probably
reflects low hardness of the lacquer coating produced from waterborne product
dried in the air in relation to much harder substrate which was beech veneer. Nevertheless, it should be noticed that average thickness of the lacquer coating on
71
furniture surface PM-6, which was about 90 μm, limited the influence of the substrate material on the coating’s scratch resistance.
Based on the values of scratch resistance final results, presented in fig. 1-6,
the analysis of their variability was carried out amongst laboratories participating
72
Jarosław Banecki
in the comparative studies of a given furniture surface. Fig. 7 illustrates results
of that analysis carried out for particular tested surfaces within each of the two
test series separately. The values of variability coefficient of the final result of
scratch resistance suggest that reproducibility of the final result of the test carried
out using method A according to TS 15186 was not satisfactory for furniture
surfaces PM-2 and PM-4 within both test series no. I and test series no. II. The
variability of final results obtained by individual participants of the comparative
studies for furniture surfaces PM-1 and PM-5 was at the level close to 9% (in
test series no. I) and to 10% (in test series no. II). Therefore, reproducibility of
the test final result for those objects was clearly better than in the case of surfaces PM-2 and PM-4. The final results determined for furniture surfaces PM-3
and PM-6 were characterised by relatively lowest variability, which indicates the
best reproducibility of the test final result obtained for those surfaces. It should
be noticed that furniture surface PM-3 demonstrated high reproducibility of the
scratch resistance final result in individual laboratories, especially in test series
no. II (fig. 7).
Fig. 7. Variability of final results of surface resistance to scratching among the laboratories participating in comparative tests, depending on the furniture surface
examined and the test series
Rys.7. Zmienność końcowych ocen odporności na zarysowanie w laboratoriach uczestniczących w badaniu porównawczym, w zależności od badanej powierzchni meblowej oraz serii
badawczej
Averaging the values of variability coefficient of scratch resistance final result
for all tested furniture surfaces, separately within each of the test series, allows a
statement that in both test series the average level of variability of final results in
5 laboratories participating in the comparison was around 10% (νav.=9.2% for test
series no. I and νav.=10.8% for test series no. II), see fig. 7.
73
Table 2 presents comparison of scratch resistance final results determined for
particular furniture surfaces within the two consecutive test series in each of the
laboratories participating in the comparative studies. Taking advantage of the values of final results given in this table, it was verified whether defined repeatability
criterion was fulfilled for the individual objects of comparative tests. Based on the
results of the verification, it may be said that only for two of six tested furniture
surfaces, i.e. for surfaces PM-4 and PM-6, the assumed repeatability criterion was
met irrespective of test performer.
Table 2 also gives calculated percentage shares of furniture surfaces for which
the observed convergence of scratch resistance final results was consistent with
defined repeatability criterion within each of the laboratories participating in the
studies. In the case of three participants of the comparative tests, i.e. LAB1, LAB2,
and LAB5, such a convergence of final results was observed for four of six tested
surfaces; whilst in the other two laboratories, i.e. LAB3 and LAB4, fulfilment of
assumed repeatability criterion was observed for all tested surfaces which meant
100% repeatability of scratch resistance final results (fig. 8). Taking into consideration percentage shares of furniture surfaces for which the defined criterion was
fulfilled, calculated for individual comparative studies participants, average repeatability of the test final result was determined for all 5 laboratories taking part in
the comparison. The calculated average value was 80% (fig. 8). This value was by
around 10% lower compared to repeatability of scratch resistance final results determined by using the same test method, but for a set of 11 various furniture surfaces tested exclusively in the ITD laboratory [Banecki, Krzoska-Adamczak 2007].
Fig. 8. Repeatability of the final result of surface resistance to scratching
Rys.8. Powtarzalność końcowego wyniku badania odporności powierzchni na zarysowanie
PM – 1
PM – 2
PM – 3
PM – 4
PM – 5
PM – 6
Code of furniture
surface tested
Spełnianie kryterium
powtarzalności 1)
Repeatability criterion fulfilment 1)
11.0
7.0
14.0
10.0
13.0
6.0
10.0
5.0
14.0
10.0
11.0
5.0
powtarzalności 1)
66.7
+
–
+
+
–
+
13.0
8.0
14.0
11.0
15.0
7.0
12.0
7.0
15.0
11.0
15.0
7.0
100.0
+
+
+
+
+
+
powtarzalności 1)
12.0
7.0
16.0
11.0
13.0
6.0
12.0
7.0
15.0
11.0
14.0
6.0
Test
Test
series I series II
I seria II seria
100.0
+
+
+
+
+
+
10.0
8.0
13.0
9.0
15.0
6.0
12.0
8.0
15.0
9.0
14.0
6.0
Test
Test
series I series II
I seria II seria
LAB 5
66.7
–
+
–
+
+
+
2)
1)
Powtarzalność końcowego wyniku badania obliczono jako udział procentowy badanych powierzchni meblowych, dla których w I i II serii badawczej
stwierdzono zbieżność końcowych ocen odporności na zarysowanie zgodną ze zdefiniowanym kryterium powtarzalności.
Znak “+” oznacza, że zdefiniowane kryterium powtarzalności końcowego wyniku badania zostało spełnione, natomiast znak “–” wskazuje, że to
kryterium nie zostało spełnione.
Final result repeatability was calculated as the ratio of quantity of furniture surfaces which fulfil defined repeatability criterion to total quantity of
furniture surfaces subjected to scratch tests, expressed in percentage.
66.7
–
–
+
+
+
+
Test
Test
series I series II
I seria II seria
2)
14.0
8.0
15.0
14.0
13.0
6.0
Test
Test
series I series II
I seria II seria
LAB 2
powtarzalności 1)
Mark “+” means that defined final result repeatability criterion was fulfilled; whereas mark “–” indicates that this criterion was not fulfilled.
12.0
6.0
16.0
13.0
12.0
6.0
Test
Test
series I series II
I seria II seria
LAB 1
Final result of surface resistance to scratching [N]
Końcowa ocena odporności na zarysowanie [N]
LAB 3
LAB 4
1)
Repeatability2)
[%]
powtarzalności 1)
Tabela 2. Ocena powtarzalności końcowego wyniku badania odporności na zarysowanie w dwu seriach badawczych w zależności od wykonawcy badania porównawczego
Table 2. Evaluation of scratch tests final results repeatability within two test series depending on the participant of comparative studies
Kod badanej
powierzchni meblowej
Powtarzalność2) [%]
74
Jarosław Banecki
75
Differentiation of tested furniture surfaces is illustrated in fig. 9 by the width
of the dispersion interval of final results of scratch resistance of those surfaces.
Data presented in fig. 9 allows a statement that the average width of the dispersion
interval of final results calculated for all comparative studies participants was 9
N in test series no. I and 8.8 N in test series no. II. Therefore, it may be accepted
that at the level of the average values, the differentiation of tested surfaces was
very similar in test series no. I and no. II. Taking into account unit values, it should be noticed that in the case of laboratories LAB1 and LAB4 the width of the
dispersion interval of final results in test series no. I exceeded the average value
and reached 10 N; whereas in test series no. II the width of that interval was at
the level of the average value (9 N). In the case of laboratory LAB3 the widths
of dispersion of final results were the same in both test series and distinctly less
than the average value. Similarly as in the case of labolatory LAB3, final results
obtained by laboratory LAB5 also were evenly dispersed in both test series, but
the width of their dispersion corresponded with the average value (fig. 9).
Fig. 9. Dispersion intervals of final results of scratch resistance of furniture surfaces
examined depending on the participating laboratory and the test series
Rys.9. Przedziały rozproszenia wartości końcowych ocen odporności na zarysowanie zbadanych powierzchni meblowych w zależności od wykonawcy badania i serii badawczej
Table 3 presents values of the furniture surface differentiation degree while
using method A according to TS 15186. The values were calculated based on the
widths of dispersion intervals of scratch resistance final results. Depending on the
test performer, calculated values fluctuated between 42% and about 53% in test
series no. I and between 42% and 47% in test series no. II. In table 3 variability
of the furniture surface differentiation degree among laboratories participating in
the comparison was evaluated. The values of variability coefficient given in table
3 suggest that variability of the surface differentiation degree within the set of fur-
76
Jarosław Banecki
niture surfaces used in studies in 5 different laboratories was at a level lower than
10%, which allows a statement that the parameter demonstrated low variability,
taking into account the scale of comparative studies carried out (i.e. the number of
participants and the number of objects tested).
Table 3. Differentiation of furniture surfaces tested depending on the participant of
comparative studies and variability of furniture surface differentiation degree for all
participating laboratories
Tabela 3. Różnicowanie badanych powierzchni meblowych w zależności od wykonawcy badania porównawczego oraz zmienność wartości stopnia zróżnicowania powierzchni meblowych w laboratoriach uczestniczących w porównaniu
LAB 5
Seria
badawcza
Furniture surface differentiation degree 1) [%]
Stopień różnicowania powierzchni meblowych 1) [%]
Variability coefficient [%]
LAB 4
Współczynnik zmienności [%]
LAB 3
Standard deviation [%]
LAB 2
Odchylenie standardowe [%]
LAB 1
Average value [%]
Test series
Średnia arytmetyczna [%]
Comparative studies participant’s code
Kod wykonawcy badania porównawczego
Test series
no. I
52.6
42.1
42.1
52.6
47.4
47.4
4.7
9.9
Test series
no. II
47.4
47.4
42.1
47.4
47.4
46.3
2.1
4.6
I seria
II seria
1)
Expresses the ability to differentiate tested furniture surfaces as regards linear scratch resistance
1) determined by method A acc. to TS 15186. This parameter was calculated according to formula
(1).
Wyraża zdolność do różnicowania powierzchni meblowych ze względu na ich odporność na
zarysowanie prostoliniowe określoną przy użyciu metody A wg TS 15186. Wskaźnik ten obliczono
stosując równanie (1).
Conclusions
Based on the results of studies conducted and analyses done, the following conclusions may be formulated:
1. Reproducibility of test final result, expressed by the value of variability coefficient of scratch resistance final result determined by method A according to
TS 15186, is diverse depending on the tested furniture surface and assumes
values from 2.7% (the highest reproducibility for surface marked with the
code PM-3) to 15.6% (the lowest reproducibility for surface marked with the
code PM2).
77
2. For most of tested furniture surfaces reproducibility of test final result is higher in the first test series (I) than in the second test series (II), and differences
in the values of final result variability coefficient between the two test series
range from 1.3% to 5.5%, depending on the tested surface.
3. In 4 industrial laboratories and in the ITD laboratory the average variability
coefficient of scratch resistance final results determined by the above-mentioned test method for the furniture surface set used was at the level of 9.2% in
test series no. I and 10.8% in test series no. II.
4. Repeatability of test final result, expressed by the percentage share of furniture surfaces fulfilling defined repeatability criterion, was at the level of 66.7%
or 100%, depending on the comparative studies participant.
5. In 4 industrial laboratories and in the ITD laboratory the average repeatability
of the final result of scratch test, carried out using the above-mentioned test
method, for six tested furniture surfaces was at the level of 80%.
6. Differentiation of furniture surfaces tested using the above-mentioned test
method, expressed by the value of furniture surface differentiation degree,
fluctuates between 42% and around 53% in test series no. I and between 42%
and 47% in test series no. II, depending on the comparative test performer.
7. In 4 industrial laboratories and in the ITD laboratory variability coefficient of
differentiation degree of the six lacquered furniture surfaces was at the level
of 9.9% in comparative test series no. I and 4.6% in comparative test series
no. II.
References
Banecki J., Krzoska-Adamczak Z., Nowaczyk M. [2004]: New test method for evaluation
of furniture surface resistance to scratching. Congress papers, 4th International Woodcoatings Congress, paper no. 20, Hague
Banecki J., Krzoska-Adamczak Z. [2007]: Comparative studies of chosen test methods
applied for evaluation of furniture surface resistance to scratching. Drewno-Wood [50]
177:119 - 138
Emmler R., Perez R., Caon C., Roux M.L., Bogelund J., Calver S., Van de Velde B.,
Adamczak Z. [2004]: Developments of test methods on wear resistance and long-term
stability for furniture surfaces. Congress papers, 4th International Woodcoatings Congress, paper no. 19, Hague
Emmler R., Nothelfer-Richter R. [2005]: Scratch-proofing. European Coatings Journal [1-2]:
36 - 40
Emmler R., Perez R., Caon C., Roux M.L., Bogelund J., Calver S., Van de Velde B.,
Adamczak Z. [2005]: Testing furniture surfaces. Standard methods for wear resistance
and long-term stability. European Coatings Journal [9]: 30 – 33
Krzoska-Adamczak Z. [1996]: Wymagania i metody oceny jakości powierzchni mebli
w porównaniu z normami niektórych krajów europejskich. Nowe technologie, obrabiarki, urządzenia, materiały i akcesoria dla meblarstwa. Materiały szkoleniowo-promocyjne
78
Jarosław Banecki
z seminarium dla głównych technologów i kierowników laboratoriów fabryk mebli. Zakopane 6-14.10.1995. Wydawnictwo ITD Poznań: 15 – 21
Krzoska-Adamczak Z. [1999]: Metody badań i kryteria oceny jakości powierzchni mebli
w porównaniu z obowiązującymi w krajach Unii Europejskiej. Nowe technologie, obrabiarki, urządzenia, materiały i akcesoria dla meblarstwa. Materiały szkoleniowo-promocyjne z seminarium dla głównych technologów i kierowników laboratoriów fabryk mebli.
Zakopane 22-29.09.1998. Wydawnictwo ITD Poznań: 59 – 64
Krzoska-Adamczak Z. [2001]: Jak bada się powłoki lakierowe na drewnie ? Lakiernictwo
Przemysłowe [10], 2: 16 – 19
Krzoska-Adamczak Z., Nowaczyk M. [2004a]: Methodical investigations for evaluation of
furniture surface resistance to scratching – Part 1. Drewno-Wood [47] 171: 5 – 30
Krzoska-Adamczak Z., Nowaczyk M. [2004b]: Methodical investigations of evaluation of
furniture surface resistance to scratching – repeatability and reproducibility of the test
method – Part 2. Drewno-Wood [47] 172: 5 – 20
Lange J., Luisier A., Hult A. [1997]: Influence of cross link density glass transition temperature and addition of pigment and wax on the scratch resistance of an epoxy coating.
Journal of Coatings Technology [69] 872: 77-82
Paprzycki O., Serafinowska L. [1990]: Oznaczanie odporności mebli na zarysowanie. Przem.
Drzew. [41] 11:1-3
Poitoux M. [2006]: How to improve the performances of coatings by using UV technology ?
Conference papers, 7th International Conference on “Advances in Coatings Technology”,
paper no. 28, Warsaw
Shen W. [2006a]: Characterization of mar/scratch resistance of polymeric coatings. Part I. J.
Coatings Technol. [3] 3:54 – 59
Shen W. [2006b]: Characterization of mar/scratch resistance of polymeric coatings. Part II. J.
Coatings Technol. [3] 4:44 - 51
List of standards
BN-78/6110-03 Wyroby lakierowe – Pomiar twardości powłok metodą ołówkową
EN 438-2:1991 Decorative high-pressure laminates (HPL) – Sheets based on thermosetting
resins – Part 2: Determination of properties
EN 438-2:2005 High-pressure decorative laminates (HPL) – Sheets based on thermosetting
resins (Usually called laminates) – Part 2: Determination of properties
ISO 1518:1992 Paints and varnishes – Scratch test
PN-65/C-81527 Wyroby lakierowe – Próba odporności powłok na zarysowanie
PN-88/F-06100-11 Meble – Metody badań właściwości powłok lakierowych i laminowych –
Oznaczanie twardości
prEN 15186:2010 Furniture – Assessment of the surface resistance to scratching (draft)
SIS 839117:1973 Furniture and fittings for housing – Determination of surface resistance to
scratches
TS 15186:2005 Furniture – Assessment of the surface resistance to scratching
79
BADANIA PORÓWNAWCZE ODPORNOŚCI MEBLOWYCH
POKRYĆ LAKIEROWYCH NA ZARYSOWANIE
PROSTOLINIOWE Z ZASTOSOWANIEM METODY
WEDŁUG TS 15186:2005
Streszczenie
Praca stanowiła kontynuację wcześniejszych badań, których efektem było opracowanie
oryginalnej metody oceny odporności powierzchni mebli na zarysowanie, a następnie
określenie jej podstawowych cech i zbadanie korelacji w ramach badań porównawczych
z metodami dotychczas stosowanymi do oznaczania odporności powierzchni na zarysowanie. Kolejnym etapem były międzylaboratoryjne badania porównawcze z udziałem
laboratoriów przemysłowych w zakresie oceny odporności na zarysowanie prostoliniowe wybranych lakierowanych powierzchni meblowych z wykorzystaniem metody A według TS 15186. Wybrane rezultaty tego etapu pracy posłużyły dalszej walidacji tej metody badawczej.
Celem pracy było określenie odtwarzalności i powtarzalności wyników badań odporności powierzchni meblowych na zarysowanie prostoliniowe, wykonanych w warunkach
laboratoriów przemysłowych i laboratorium ITD z zastosowaniem metody badawczej
A opisanej w standardzie technicznym TS 15186, a także określenie zdolności zastosowanej metody do różnicowania powierzchni meblowych wykończonych różnymi wyrobami
lakierowymi.
Program pracy obejmował między innymi: zaznajomienie wybranych laboratoriów przemysłowych z nową metodą badawczą, wykonanie przez uczestników badań porównawczych dwu serii badań odporności na zarysowanie każdej z sześciu lakierowanych powierzchni meblowych, przeprowadzenie analizy wyników badań ze względu na wybrane
cechy zastosowanej metody badawczej (odtwarzalność, powtarzalność końcowego wyniku badania, różnicowalność powierzchni meblowych). Przedmiotami badań były płytowe
elementy meblowe o powierzchniach uszlachetnionych pokryciami wytworzonymi z pigmentowanych lub przezroczystych wyrobów lakierowych.
W wyniku przeprowadzonych badań porównawczych stwierdzono, że odtwarzalność
końcowego wyniku badania, wyrażana za pomocą wartości współczynnika zmienności
końcowej oceny odporności na zarysowanie, jest zróżnicowana w zależności od badanej
powierzchni meblowej. Średni współczynnik zmienności końcowych ocen odporności na
zarysowanie, określonych przy użyciu powyższej metody we wszystkich 5 laboratoriach
uczestniczących w porównaniu, kształtuje się na poziomie około 9% w I serii badawczej,
oraz około 11% w II serii badań. Powtarzalność końcowego wyniku badania, wyrażana
procentowym udziałem powierzchni meblowych, dla których zostało spełnione zdefiniowane kryterium powtarzalności, w zależności od wykonawcy badania porównawczego
kształtuje się na poziomie około 67% lub 100%. Natomiast, średnia powtarzalność końcowego wyniku badania kształtuje się na poziomie 80%. Zdolność do różnicowania badanych powierzchni meblowych, wyrażana wartością stopnia różnicowania powierzchni
meblowych, waha się od 42% do około 53% w I serii badań oraz od 42% do 47% w II serii badawczej, zależnie od wykonawcy badania porównawczego. Oszacowana zmienność
80
Jarosław Banecki
stopnia różnicowania sześciu różnych lakierowanych powierzchni meblowych, badanych
w 5 laboratoriach uczestniczących w porównaniu, kształtuje się na poziomie poniżej 10%
zarówno w I, jak i II serii badań porównawczych.
Słowa kluczowe: powierzchnia meblowa, odporność powierzchni na zarysowanie prostoliniowe,
odtwarzalność końcowego wyniku badania, powtarzalność końcowego wyniku
badania, różnicowanie powierzchni meblowych.
Grzegorz Kowaluk, Magdalena Komorowicz, Magdalena Witczak,
Dorota Fuczek1
FORMALDEHYDE CONTENT IN AND VOC RELEASE
FROM PARTICLEBOARDS MADE OF FIBROUS CHIPS
The aim of this research was to investigate formaldehyde content in and volatile
organic compounds release from particleboards produced from fibrous chips. The
object of the tests were panels produced from fibrous chips of black locust Robinia
Pseudoacacia L. and willow Salix Viminalis L., as well as from typical industrial
particles. The results show that formaldehyde content in the panels produced from
willow fibrous chips is similar to the content in the panels made of industrial particles. The concentration of total volatile organic compounds measured after 4 weeks
of storage is significantly lower than the required by the existing regulations.
Keywords: formaldehyde, VOC, HCHO, fibrous chips, particleboard, willow,
black locust
Introduction
The possibility of furniture panel production from willow and black locust fibrous
chips was confirmed by mechanical strength tests and machining experiments
[Kowaluk 2009; Kowaluk et al. 2010]. To produce a complete characteristic of
the new, designed material the information about its hygienic properties, such as
formaldehyde content and concentration of volatile organic compounds, is needed. An exceedance of safe levels of concentration of some chemical compounds,
including formaldehyde, hexanal and other VOC, can be dangerous to human
health. The issue is especially important when particles are bound using ureaformaldehyde resin. A systematic reduction of the perforator value during the last
Grzegorz Kowaluk, Wood Technology Institute, Poznan, Poland
Magdalena Komorowicz, Wood Technology Institute, Poznan, Poland
Magdalena Witczak, Wood Technology Institute, Poznan, Poland
Dorota Fuczek, Wood Technology Institute, Poznan, Poland
82
Grzegorz Kowaluk, Magdalena Komorowicz, Magdalena Witczak, Dorota Fuczek
5 decades [Roffael 2006] can be an effect of the attention given to hygienic indoor
environment. It is a common knowledge [Yrieix et al. 2010] that in Europe people
spend almost 90% of their time inside buildings. It can substantiate the validity
of research on formaldehyde content in and VOC release from the investigated
panels which can be used as indoor equipment in the future.
The aim of this research was to investigate formaldehyde content in and
volatile organic compounds release from particleboards produced from fibrous
chips. The tested objects were panels made of fibrous chips of black locust Robinia Pseudoacacia L. and willow Salix Viminalis L. For comparison panels from
typical industrial particles were produced at the laboratory scale as well.
Particleboards
The investigated 3-layer panels were produced at the laboratory scale from fibrous
chips obtained from 2 years old offshoots of black locust Robinia Pseudoacacia
L. and 2 years old offshoots of willow Salix Viminalis L., as well as from industrial
softwood particles. The main production parameters were: density (assumed) 600
and 660 kg/m3, core layer particles’ mesh size between 2 and 8 mm, thickness
16 mm, face layers share 32 %, urea-formaldehyde resin Silekol W-1C, resination
in the core 8 % and in the face layers 12 %, pressing time coefficient 10 s/mm.
Finally, 6 types of the panels were produced: 2 panels of different density from industrial particles (ip600 and ip660), 2 panels of different density from black locust
(r600 and r660) and 2 panels of different density from willow (w600 and w660).
Fig. 1. Bending strength and modulus of elasticity of investigated panels
Rys. 1. Wytrzymałość na zginanie oraz moduł sprężystości badanych płyt
Formaldehyde content in and voc release from particleboards made of fibrous chips
83
The tests of the produced panels showed that density variations between the assumed and the real values were less than 5 %. The mechanical parameters of the
panels are presented in fig. 1. The panels were calibrated on the industrial grinding
machine to achieve equal panel thickness as well as better surface roughness.
A layer of the thickness of about 0.3 mm was removed from each side of a calibrated panel. After grinding, particleboards were conditioned to the equilibrium
moisture content at a temperature of 20ºC and relative humidity of 65 %.
The innovation in this study is the new type of the particles used to produce
furniture particleboards. As it can be seen in fig. 2, fibrous chips are totally different from industrial chips. Fibrous chips are longer and have many free fibres
at the ends as well as on the whole body. They are springier. The average bulk density of fibrous chips for core layer was about 20-30 kg/m3; while typical industrial
core layer chips have bulk density about 150 kg/m3.
Fig. 2. The differences between the form of fibrous chips (a) and the form of typical
industrial particles (b)
Rys. 2. Różnice pomiędzy postacią wiórów włóknistych (a) i postacią typowych wiórów
przemysłowych (b)
Formaldehyde content measurement
The formaldehyde content measurement was conducted according to PN-EN
120:1994 standard. Two parallel tests of one type of the panel were carried out.
The results of the tests represent formaldehyde content in panels of moisture content converted into 6.5%. All panels produced at the laboratory scale were tested
for formaldehyde content.
84
Volatile organic compounds (VOC) measurement
Qualitative analysis and quantitative determination of VOC was carried out
on GC/MS TRACE 2000 Thermoquest/Finnigan apparatus, equipped with a mass
detector Finnigan Trace MS and a capillary column RTX-VMS 30m × 0.25mm
× 1.4 µm, using thermal desorption technique according to PN-EN ISO 160009:2006. Samples of the panels were prepared according to PN-EN ISO 1600011:2006 and samples of emitted gas for analyses were taken in line with PN-EN
ISO 16017-1:2006 regulations. The following parameters of the chamber were
used: temperature 23±2ºC, air relative humidity 50±5 %, air exchange rate 1 per
hour, chamber loading rate 1 m2/m3, chamber capacity 0.025 m3. The following
samples were taken for VOC tests: r660, w660 and industrial 3-layer particleboard with the density of 645 kg/m3. The VOC emission test was conducted four
weeks after the production date, including conditioning time.
Results and discussion
Formaldehyde content
The results of the measurement of formaldehyde content in investigated panels
are presented in fig. 3. As it can be seen, panels produced from black locust fibrous
chips were characterised by the highest formaldehyde content. The panel of lower
density had slightly higher formaldehyde content.
Fig. 3. Formaldehyde content in investigated panels
Rys. 3. Zawartość formaldehydu w badanych płytach
This remark is true also for panels produced from willow fibrous chips. However,
taking into account the notice from PN-EN 120:1994 standard stating that 20 %
85
differences in formaldehyde content between two parallel tests of the same panel
can be acceptable, the presented differences in formaldehyde content between
panels of different densities are of no practical significance.
The average formaldehyde content was comparable in the case of panels produced from industrial particles (ip600 and ip 660) and from willow fibrous chips
(w600 and w660).
In the light of the study of Weigl et al. [2009], where softwood had higher
wood-borne formaldehyde content, it seems interesting that higher formaldehyde
content was found in panels produced from willow and black locust, i.e. from
hardwood species.
Volatile organic compounds (VOC)
From the point of view of particleboard end-user it is worth mentioning that the
emission of VOC from tested panels made of fibrous chips, as well as from the
industrial panel, was significantly low (table 1). This observation was made based
on the comparison of the further presented results of VOC measurements with the
research of Dziewanowska-Pudliszak and Gaca [2004] where industrial 3-layer
and 16 mm thick particleboards were tested. The above-mentioned researchers
obtained the following results of tests for total VOC (TVOC): 2269 mg/m3 after
5h, 1279 mg/m3 after 24h, and 921 mg/m3 after 48h. One of the reasons for such
a low emission can be the 4 week long storage time of tested panels. Such a storage time before tests gives more useful information about the VOC emission level. The research of Kowaluk et al. [2010], which were conducted on particleboard
samples conditioned unwrapped for 4 weeks, proved that panels made of maritime
pine and glued with urea formaldehyde (UF) resin contained significant concentrations of α-pinene and hexanal (50.3 mg/m3 and 65.5 mg/m3, respectively, after
3 day emission test in a chamber). In panels produced from willow fibrous chips the
concentration of hexanal was almost twice as high as the Yrieix’s result (121 mg/
m3), but the amount of α-pinene was half the Yrieix’s result (25 mg/m3) after 2 day
emission test in the chamber (table 1). The concentration of the above-mentioned
compounds for the panel made of black locust fibrous chips equalled 1 or less
than 1. The variation of the concentrations of α-pinene and hexanal for industrial
panels was high, but after 2 day emission test in the chamber the amount of the
above-mentioned compounds was lower than for the panels tested by Yrieix et
al. [2010]. The low emission of phenolic compounds from black locust panel can
be confirmed by the conclusions of Dünisch et al. [2010] stating that the juvenile
wood of black locust has low content of such a component. In that research the
amount of VOC sum (TVOC) was also 218.1 mg/m3. In the light of this result,
panels produced from willow were characterised by TVOC of about 431 mg/m3,
panels from black locust by TVOC of 50 mg/m3, and industrial panel by TVOC
of 117 mg/m3. The above-mentioned values do not exceed the TVOC limits
86
proposed by the Committee for Health-related Evaluation of Building Products
[AgBB 2008].
Table 1. The concentration of chemical compounds in the chamber air for tested
panels
Tabela 1. Stężenie związków chemicznych w powietrzu komory dla badanych płyt
Concentration in the chamber air [mg/m3]
Stężenie w powietrzu komory [mg/m3]
Exposure time [h]
Chemical compound
Czas ekspozycji [h]
Związek chemiczny
48
industrial
w660
r660
acetone/aceton
<1
acetic acid/kwas octowy
77
pentanal/pentanal
11
23
5
8
6
5
19
6
przemysłowa
toluene/toluen
5
pentanol/pentanol
25
hexanal/heksanal
121
ethylbenzene/etylobenzen
15
4
25
<1
1
<1
<1
<1
12
1
8
o-xylene/o-ksylen
14
1
7
<1
6
15
2
m- and p-xylene/
m- i p-ksylen
α-pinene/α-pinen
25
heptanal/heptanal
17
3-carene/3-karen
5
benzaldehyde/benzaldehyd
15
octanal/oktanal
26
6
1
<1
<1
<1
<1
7
4
6
<1
<1
<1
117
2-ethyl-1-hexanol/
2-etylo-1-heksanol
phenol/fenol
12
acetophenone/acetofenon
12
decanal/dekanal
32
<1
<1
8
431
50
SUM = TOTAL VOC
SUMA = TVOC
87
Conclusions
Presented results are promising as regards the production of particleboards from
tested raw materials and particles (fibrous chips). The following conclusions
can be drawn from this study:
–– formaldehyde content in panels produced from fibrous chips of Robinia Pseudoacacia L. was higher than in panels produced from fibrous chips of Salix
Viminalis L.,
–– after 4 weeks of storage the concentration of volatile organic compounds, measured in the 48 h of exposure time, was the highest for panels produced from
Salix Viminalis L. fibrous chips and the lowest for panels from Robinia Pseudoacacia L. fibrous chips,
–– compared with other laboratory tests [Dziewanowska-Pudliszak and Gaca
2004, Roffael 2006], VOC concentration for panels produced from fibrous
chips was significantly lower than for industrial particleboards.
Acknowledgements
This paper received financial support of the Polish Ministry of Science and Higher
Education under grant number N309 1068 33.
References
AgBB [2008]: Health-Related Evaluation Procedure for Volatile Organic Compounds Emissions (VOC and SVOC) from Building Products. <http://www.umweltbundesamt.de/produkte-e/bauprodukte/archive/AgBB-Evaluation-Scheme2008.pdf>
Dünisch O., Richter H.-G., Koch G. [2010]: Wood properties of juvenile and mature heartwood in Robinia pseudoacacia L. Wood Sci. Technol. 2010 [44]:301–313
Dziewanowska-Pudliszak A., Gaca P. [2004]: How many organic compounds does the furniture emit? Gazeta Drzewna 11[73]: 15, 16 (in polish)
Kowaluk G. [2009]: Influence of the method of milling on the geometry of fibrous chips and
bending strength of produced particleboards. Proc. 3rd Int. Sc. Conf. Woodworking Techniques. Zalesina: 323-331
Kowaluk G., Zbiec M., Beer P. [2010]: The quality of milling of the particleboards produced
from fibrous chips. Ann. WULS-SGGW, For. and Wood Technol. 71
Roffael E. [2006]: Volatile organic compounds and formaldehyde in nature, wood and wood
based panels. Holz als Roh- und Werkstoff [64]: 144–149
Schäfer M., Roffael E. [2000]: On the formaldehyde release of wood. Holz als Roh- und
Werkstoff [58]: 259-264
Weigl M., Wimmer R., Sykacek E.; Steinwender M. [2009]: Wood-born formaldehyde varying with species, wood grade, and cambial age. Forest Product Journal [59] 1/2: 88-92
Yrieix Ch., Dulaurent A., Laffargue C., Maupetit F., Pacary T., Uhde E. [2010]: Characterization of VOC and formaldehyde emissions from a wood based panel: Results from
an inter-laboratory comparison. Chemosphere [79]: 414–419
88
List of standards
ISO 16000-6:2004 Indoor air – Part 6: Determination of volatile organic compounds in indoor
and test chamber air by active sampling on Tenax TA sorbent, thermal desorption and gas
chromatography using MS/FID
PN-EN 120:1994 Wood based panels. Determination of formaldehyde content. Extraction method called the perforator method
PN-EN ISO 16000-9:2006 Indoor air – Part 9: Determination of the emission of volatile organic compounds from building products and furnishing - Emission test chamber method
PN-EN ISO 16000-11:2006 Indoor air – Part 11: Determination of the emission of volatile
organic compounds from building products and furnishing - Sampling, storage of samples
and preparation of test specimens
PN-EN ISO 16017-1:2006 Indoor. Ambient and workplace air - Sampling and analysis of volatile organic compounds by sorbent tube/thermal desorption/ capillary gas chromatography - Part 1: pumped sampling
ZAWARTOŚĆ FORMALDEHYDU I EMISJA VOC
PŁYT WIÓROWYCH WYTWORZONYCH Z WIÓRÓW
WŁÓKNISTYCH
Streszczenie
Celem badań było określenie zawartości formaldehydu w płytach wiórowych wytworzonych z wiórów włóknistych i emisji lotnych związków organicznych z tych płyt. Do
badań użyto wiórów włóknistych z dwuletnich odrostów korzeniowych robinii (Robinia Pseudoacacia L.) oraz wierzby (Salix Viminalis L.), jak również typowych wiórów
przemysłowych. Badania wykazały, iż zawartość formaldehydu w płytach wytworzonych
z wierzby jest zbliżona do zawartości formaldehydu w płytach z wiórów przemysłowych.
Stężenie lotnych związków organicznych, mierzone po 4 tygodniach przechowywania
płyt, jest istotnie mniejsze niż obowiązujące ograniczenia.
Słowa kluczowe: formaldehyd, VOC, HCHO, wióry włókniste, płyta wiórowa, wierzba, robinia
DONIESIENIA NAUKOWE - RESEARCH PAPERS
Magdalena Witczak, Małgorzata Walkowiak, Wojciech Cichy1
PRE-TREATMENT OF BIOMASS BY TORREFACTION –
PRELIMINARY STUDIES
Torrefaction is a mild pre-treatment of biomass at the temperatures range from
200°C to 300°C. This report presents preliminary studies of torrefaction process
for different types of raw material. A torrefied product has a brown/black colour,
reduced moisture content, and increased heating value (HHV and LHV). It has favourable properties for application as a fuel for gasification and combustion.
Keywords: torrefaction, biomass pre-treatment, TOP process, TOP pellets
Introduction
Biomass is an important renewable energy source. International obligations of
Poland and the energy sector concerning the production of renewable energy result in a situation where biomass could be burnt in co-firing process as a biofuel
[Rozporządzenie…2008; Obwieszczenie…2009].
Biomass as a biofuel has such advantages as renewability in a short period of
time (it is dependent on plant species growing from few months to ten years) and
relatively high energy potential. The high heating value of biomass (15-24MJ/kg)
is comparable with the worst types of coal.
The disadvantages of biomass, like its high moisture content and hygroscopic
nature, make this material requiring drying and storage in special conditions and
in small particles after harvesting. The raw biomass has a lower heating value
(few MJ/kg). Moreover, plant biomass has very diverse properties (different amounts of elements like chlorine, sodium, and potassium). All described features of
Magdalena Witczak, Wood Technology Institute, Poznan, Poland
Małgorzata Walkowiak, Wood Technology Institute, Poznan, Poland
Wojciech Cichy, Wood Technology Institute, Poznan, Poland
90
Magdalena Witczak, Małgorzata Walkowiak, Wojciech Cichy
biomass cause that harvesting, transport, storage and preparation of this material
for combustion become troublesome and uneconomic.
Modification with the object ameliorates many or all deficiencies of biomass.
Thermal modification of wood improves hydrophobic properties, increases its natural resistance and extends durability. This form of thermal processing of plant
biomass is a preparation process for combustion known as torrefaction.
In the literature torrefaction is defined as mild or slow pyrolysis, high-temperature drying, roasting, wood cooking and wood browning. The name of torrefaction is adopted from roasting of coffee beans, which is performed at lower temperature and using air. Nevertheless, an important mechanical effect of torrefaction
on biomass is supposed to be similar to its effect on coffee beans which is their
resulting brittle structure.
In the 1930’s the principles of torrefaction were first reported in relation to
woody biomass. The process was carried out as a part of the biomass application to produce a gasifier fuel [Bergman 2005]. In 1980 Bourgois and Guyonnet
described torrefied wood as an efficient biofuel for combustion and gasification
[Lipinsky, Arcate, Reed 2002]. The combustion process of torrefied wood and torrefied biomass was studied by researchers since the 1990’s [Bergman et al. 2005;
Yan-jun et al. 2002; Ahajji et al. 2009].
Torrefaction is a thermo-chemical process at a temperature of 200-300oC. It
is carried out under atmospheric conditions and in the absence of oxygen (for
example nitrogen [Prins, 2005]. The main product is solid state substance which
is often called a torrefied biomass or char. The efficiency of mass and energy in
torrefaction process depends on the temperature, time, and type of biomass. In
addition, the process is characterised by low particle heating rates (<50oC/min)
and the time of the process is about an hour.
Fig. 1 provides a typical mass and energy balance of torrefaction [Bergmann et
al. 2005]. In the process 70% of the mass is retained as a solid product containing
90% of the initial energy content. The high value of energy in torrefied product
influences the improvement of fuel properties. This is in contrast to pyrolysis process which is characterised by an energy yield of 55-65% in advanced concepts.
Fig. 1. Typical mass and energy balance of the torrefaction process (M – mass, E –
energy) [Bergmann et al. 2005]
Rys. 1. Typowy rozkład masy i energii w procesie toryfikacji (M – masa, E – energia) [Bergman i in. 2005]
Pre-treatment of biomass by torrefaction – preliminary studies
91
The main product of torrefaction is a fragile and breakable material of brown,
dark-brown or black colour. Torrefied biomass is no more of hygroscopic nature
and its grindability is improved significantly. In addition, it has high biological
resistance and interesting properties as a biofuel [Bergmann et al. 2005b]. These
features make torrefied biomass very attractive for combustion and gasification
applications.
TOP process
The solution to the problems with treatment of biomass was the implementation
of pelletisation process. Compared to untreated biomass pellets are small combustion units and bring cost savings in handling and transportation. Pellets are less
vulnerable to biological degradation, for they are dry, so the periods of storage can
be longer. Pelletisation process consists of drying, size reduction, steam preconditioning, and densification. Nowadays pellets compete with coal in the Northern
Europe. Research is still being continued to improve the pellets properties. Producers mainly upgrade pellets’ durability and biological degradation. The uniformity
of pellets is difficult to establish, as the sources of quality variations are numerous.
There are large differences between softwood, hardwood or straw. Bergman described the combination of torrefaction and pelletisation as the TOP process. The
TOP process consists of the following stages: drying, torrefaction, size reduction,
densification, and cooling (fig. 2).
A. Pelletisation/Peletyzacja
B. Torrefaction/Toryfikacja
C. TOP process (torrefaction and pelletisation)/Proces TOP (toryfikacja i peletyzacja)
Fig. 2. Stages of pelletisation process, torrefaction process and TOP process [Bergman et al. 2005]
Rys. 2. Etapy procesu peletyzacji, procesu toryfikacji i procesu TOP [Bergman i in. 2005]
Table 1 provides an overview of the properties of TOP pellets in comparison
with wood, torrefied biomass and conventional wood pellets. The bulk densities
92
for TOP pellets vary in the range of 750 to 850 kg/m3 and heating value (LHV) is
contained in the range of 20-22 MJ/kg. The energy density of TOP pellets (14-18.5
GJ/m3) is better compared to sub-bituminous coal, which has a typical value of 1617 GJ/m3; while conventional wood pellets have the value of 7.8-10.5 GJ/m3. TOP
pellets produced from different types of biomass (sawdust, willow, straw, larch,
miscanthus) are similar in terms of physical properties. In the mechanical and humidity tests TOP pellets demonstrate higher durability than conventional pellets.
Table 1. Properties of wood, torrefied biomass, wood pellets and TOP pellets [Bergman et al. 2005]
Tabela 1. Właściwości drewna surowego, biomasy toryfikowanej, peletów drzewnych i peletów TOP [Bergman i in. 2005]
Properties
Unit
Wood
Torrefied
biomass
Właściwości
Jednostka
Drewno
Biomasa
toryfikowana
Moisture content
wt.%
%wag
35
MJ/kg
Wilgotność
Wood pellets
Pelety drzewne
TOP pellets
Pelety TOP
min
max
min
max
3
10
7
5
1
10.5
19.9
15.6
16.2
19.9
21.6
MJ/kg
17.7
20.4
17.7
17.7
20.4
22.7
kg/m3
550
230
500
650
750
850
-
moderate
high
Heating value (LHV)
Wartość opałowa
as received
stan roboczy
dry
stan suchy
Mass density (bulk)
Gęstość nasypowa
Pellet strength
Wytrzymałość peletów
Dust formation
Formowanie się pyłu
Hygroscopic nature
Higroskopijność
Biological degradation
Degradacja biologiczna
Handling properties
Cechy manipulacyjne
-
-
good
dobra
limited
very good
bardzo dobra
limited
średnie
wysokie
ograniczone
ograniczone
water
uptake
hydrophobic
hydrofobowe
swelling/
water uptake
pęcznienie/
absorpcja wody
poor swelling/
water uptake
słabe pęcznienie/
absorpcja wody
possible
impossible
possible
impossible
absorpcja
wody
możliwa
normal
normalne
niemożliwa
normal
normalne
możliwa
good
dobre
niemożliwa
good
dobre
Torrefaction of biomass is a new technology of producing solid biofuels with
high yield of process (92%) in comparison with pelletisation (84%) and pyrolysis
(64%) processes.
Uslu, Faaij and Bergman studied technical and economic performance of torrefaction, pyrolysis and pelletisation processes. Table 2 shows that the efficiency
93
of torrefaction process, TOP process and pelletisation process was high compared
to pyrolysis technology.
Table 2. Techno-economic comparison of torrefaction, TOP process, pelletisation and
pyrolysis [Uslu, Faaij, Bergman 2008]
Tabela 2. Techniczno-ekonomiczne porównanie procesu toryfikacji, procesu TOP, peletyzacji
i pirolizy [Uslu, Faaij, Bergman 2008]
Unit
Jednostka
Process efficiency
*
Wydajność procesu*
Energy content (LHVdry)
Zawartość energii (wartość
opałowa)
Mass density (bulk)
Gęstość nasypowa
Energy density
Gęstość energetyczna
Production costs
Koszty produkcji
Pyrolysis
Toryfikacja
Proces TOP
Peletyzacja
%
92
90.8
84 - 87
66 - 70
MJ/kg
20.4
20.3 - 22.7
17.7
17
kg/m3
230
750 - 850
500 - 650
1200
GJ/m3
4.6
14.9 - 18.4
7.8 - 10.5
20 - 30
0.17
0.19
0.15
0.19 - 0.42
58
50
54
75 - 104
Specific capital investments M €/MWth
Nakłady kapitałowe
Torrefaction TOP process Pelletisation
mln €/MWth
€/ton
€/tona
Piroliza
* This is the overall efficiency of the technology including utility fuels.
* Jest to całkowita wydajność technologii z uwzględnieniem paliw użytkowych.
This study indicates that torrefaction and TOP process are more advantageous
than pelletisation. Pyrolysis, as an alternative, has drawbacks in terms of process
efficiency and economy if compared to the other technologies.
Experimental
In preliminary studies different types of materials were used: deciduous (beech
and willow), coniferous (pine), annual plants (miscanthus, straw), and wood material (plywood). The starting point of the research was determination of mass
reduction of dry basis. This parameter should be close to 30% [Bergman 2005]. In
the model material (miscanthus) mass reduction was 30% when torrefaction was
carried out in nitrogen atmosphere at 240°C for 30 minutes with particle heating
rates 22oC/min. These conditions were used for torrefaction of all types of materials. Table 4 shows values of mass reduction, where the maximum was reached
for miscanthus 31.93% and the minimum for pine 16.17%.
94
Table 4. Value of mass reduction [wt.% db]
Tabela 4. Wartość ubytku masy [% wags.m.]
Sample
Mass reduction [wt.%db]
beech/buk
willow/wierzba
pine/sosna
miscanthus
straw/słoma
plywood/sklejka
23.70
19.80
16.17
31.93
26.48
17.47
Ubytek masy [%wags.m.]
Próbka
db: dry basis;
s.m.: sucha masa
Before and after torrefaction parameters of raw materials and torrefied materials such as: moisture content, ash content, ultimate analysis, higher heating
value (HHV) and lower heating value (LHV), were determined (table 5).
Table 5. Characteristic of raw and torrefied materials properties
Tabela 5. Charakterystyka właściwości materiałów wyjściowych i toryfikowanych
Moisture
content
Sample
Próbka
Ash content
Wilgotność
Zawartość
popiołu
wt.%
% wag
wt.%db
%wags.m.
7.23
0.47
6.79
Ultimate analysis*
[wt.%db]
Higher
Lower heating
value
heating value
Analiza elementarna Wyższa wartość Niższa wartość
opałowa
[%wags.m.]
opałowa
N
MJ/kgdb
MJ/kgs.m.
MJ/kgdaf
MJ/kgs.b.p.
47.78 5.89
0.06
19.71
18.43
1.41
48.21 5.98
0.50
19.50
18.19
7.70
0.42
48.76 6.06
0.03
20.27
19.06
7.60
0.34
47.46 6.08
3.80
19.57
18.25
9.02
4.29
45.04 5.90
0.44
18.99
17.70
8.63
3.40
47.05 6.01
0.56
19.07
17.76
3.74
0.57
53.35 5.64
0.07
19.96
18.73
C
H
Raw material:
Materiał wyjściowy:
beech
buk
willow
wierzba
pine
sosna
plywood
sklejka
miscanthus
straw
słoma
Torrefied
material:
Materiał
toryfikowany:
beech
buk
95
Table 5. Continued
Tabela 5. Ciąg dalszy
willow
wierzba
pine
sosna
plywood
sklejka
miscanthus
straw
słoma
0.91
1.57
51.60 5.63
1.26
20.49
19.26
1.85
0.37
50.66 5.57
0.03
20.67
19.35
1.80
0.41
51.92 5.75
2.00
18.56
17.31
1.68
6.51
53.23 5.23
0.60
21.04
19.90
2.37
4.65
52.56 5.37
0.50
20.37
19.20
db: dry basis; s.m.: sucha masa
daf: dry and ash free basis; s.b.p.: stan suchy bezpopiołowy
*
sulphur content <0.01%db; *zawartość siarki <0,01% s.m.
Conclusions
The research confirmed the data in the literature [Prins et al. 2006, Arias et al.
2008] saying that lower calorific value (dry and ash free basis) is higher for torrefied biomass than for raw biomass. The moisture content of the torrefied material
is much lower compared to the content of moisture in the raw material. The content of carbon in the solid torrefied material increases and the content of hydrogen decreases increasing the higher calorific value of the torrefied biomass. The
exception is plywood whose calorific value is higher in raw material. The authors
presume that this is caused by the resin contained in plywood. It is necessary to
carry out further experiments of torrefaction changing the process parameters and
to compare raw and torrefied material properties.
References
Ahajji A., Diouf P.N., Aloui F., Elbakali I., Perrin D., Merlin A., George B. [2009]: Influence
of heat treatment on antioxidant properties and colour stability of beech and spruce wood
and their extractives. Wood Sci. Technol. [43]: 69-83
Arias B., Pevida C., Fermoso J., Plaza M.G., Rubiera F., Pis J.J. [2008]: Influence of
torrefaction on the gindability and reactivity of woody biomass. Fuel Processing Technology [89]: 169-175
Bergmann P.C.A. [2005]: Combined torrefaction and pelletisation. The TOP process. Report
no. ECN-C-05-073, Petten
Bergmann P.C.A., Boersma A.R., Kiel J.H.A., Prins M.J., Ptasinski K.J., Janssen F.J.J.G.
[2005a]: Torrefaction for entrained-flow gasification of biomass. Report no. ECN-C-05-067,
Petten
Bergmann P.C.A., Kiel J.H.A. [2005b]: Torrefaction for biomass upgrading. Report no.
ECN-RX-05-180, Petten
96
Lipinsky E.S., Arcate J.R., Reed T.B. [2002]: Enhanced wood fuels via torrefaction. Fuel
Chemistry Division Preprints 47[1]: 408
Obwieszczenie Ministra Gospodarki z dnia 21 grudnia 2009 r. w sprawie polityki energetycznej państwa do 2030 r., M.P.2010.2.11
Prins M.J. [2005]: PhD thesis: Thermodynamic analysis of biomass gasification and
torrefaction. University of Eindhoven
Prins M.J., Ptasinski K.J., Janssen F.J.J.G. [2006]: Torrefaction of wood. Part 2. Analysis of
products. J. Anal. Appl. Pyrolysis [77]: 35-40
Rozporządzenie Ministra Gospodarki z dnia 14 sierpnia 2008 r. w sprawie szczegółowego
zakresu obowiązków uzyskania i przedstawienia do umorzenia świadectw pochodzenia, uiszczenia opłaty zastępczej, zakupu energii elektrycznej i ciepła wytworzonych w
odnawialnych źródłach energii oraz obowiązku potwierdzania danych dotyczących ilości
energii elektrycznej wytworzonej w odnawialnym źródle energii. Dz.U.2008.156.969; zm.
Dz.U.2010.34.182
Uslu A., Faaij A.P.C., Bergman P.C.A. [2008]: Pre-treatment technologies, and their effect on
international bioenergy supply chain logistic. Techno-economic evaluation of torrefaction,
fast pyrolysis and pelletisation. Energy [33]: 1206-1223
XIE Yan-jun, LIU Yi-xing, SUN Yao-xing [2002]: Heat-treated wood and its development
in Europe. Journal of Forestry Research 13[3]: 224-230
TORYFIKACJA JAKO PROCES OBRÓBKI BIOMASY –
BADANIA WSTĘPNE
Streszczenie
Przedstawiono wyniki uzyskane w trakcie wstępnych badań procesu toryfikacji wybranych
materiałów lignocelulozowych. Otrzymane produkty toryfikowane charakteryzowały się
brązowo-czarną barwą, niską wilgotnością oraz podwyższoną wartością ciepła spalania i wartością opałową, co wpływało korzystnie na poprawę właściwości paliwowych
badanych próbek biomasy.
Toryfikacja jest procesem łagodnej obróbki wstępnej biomasy, zachodzącym w temperaturze 200-300°C pod ciśnieniem atmosferycznym w atmosferze gazu obojętnego.
Wydajność masy i energii procesu toryfikacji jest zależna od temperatury, czasu oraz typu
biomasy poddawanej toryfikacji. Prędkość wzrostu temperatury procesu, według danych
literaturowych, nie przekracza 50°C na minutę, a czas jego trwania oscyluje najczęściej
w granicach jednej godziny. W trakcie toryfikacji następuje częściowa dekompozycja
biomasy z wydzieleniem produktów lotnych. Pożądany produkt toryfikacji jest ciałem
stałym, określanym jako biomasa toryfikowana. Uzyskane wyniki pozwalają na planowanie dalszych prac badawczych w tym zakresie.
Słowa kluczowe: toryfikacja, obróbka wstępna biomasy, TOP proces, pelety TOP
Marcin Oszust, Daniel Pieniak, Paweł Ogrodnik, Lesław Dec1
BADANIE SPADKU WYTRZYMAŁOŚCI DREWNA
ŚWIERKOWEGO MODYFIKOWANEGO TERMICZNIE
W WARUNKACH TEMPERATUR POŻAROWYCH
Modyfikowanie termiczne drewna jest jedną z nowych technologii mających na celu
poprawę jego właściwości. Drewno modyfikowane termicznie (TT) charakteryzuje
się innymi parametrami użytkowo-estetycznymi niż drewno naturalne niemodyfikowane (NTT).
Celem badań była ocena wpływu temperatur występujących w środowisku pożaru
na zmiany wytrzymałości drewna świerkowego modyfikowanego termicznie. Badania zostały wykonane na specjalnie zaprojektowanym stanowisku badawczym
z możliwością oddziaływania wysokich temperatur. Określono wartości wytrzymałości przy rozciąganiu, ściskaniu oraz zginaniu w temperaturach normalnych
i pożarowych. Zaprezentowano analizę porównawczą spadku wytrzymałości drewna świerkowego TT i drewna świerkowego NTT. Wykazano istotny wpływ temperatur pożarowych na spadek wytrzymałości badanego drewna, postępujący w kolejnych przedziałach temperatur.
Słowa kluczowe: temperatury pożarowe, drewno modyfikowane termicznie,
drewno niemodyfikowane termicznie, drewno świerkowe,
wytrzymałość.
Wstęp
Drewno jest jednym z podstawowych materiałów stosowanych w konstrukcjach
inżynierskich. Na poziomie mikrostrukturalnym drewno jest niehomogenicznym
kompozytem komórkowym, kompozycją celulozy, hemicelulozy, ligniny i innych
mniej znaczących składników [Younsi i in. 2010]. Celuloza stanowi największą
część objętości drewna, składa się ona z długich łańcuchów węglowych, które są
najistotniejsze dla wytrzymałości drewna. Hemiceluloza składa się z rozgałęzioMarcin Oszust, Szkoła Główna Służby Pożarniczej, Warszawa, Polska
Daniel Pieniak, Szkoła Główna Służby Pożarniczej, Warszawa, Polska
Paweł Ogrodnik, Szkoła Główna Służby Pożarniczej, Warszawa, Polska
Lesław Dec, Szkoła Główna Służby Pożarniczej, Warszawa, Polska
98
Marcin Oszust, Daniel Pieniak, Paweł Ogrodnik, Lesław Dec
nych polimerów amorficznych, wypełnia ona obszar pomiędzy celulozą i ligniną
w strukturze drewna. Lignina jest polimerem amorficznym odpowiedzialnym za
kohezję struktury drewna, jest ona czynnikiem „sklejającym” strukturę [Manriquez, Moraes 2010].
Drewno poddane termicznej modyfikacji jest coraz powszechniej wykorzystywane w Polsce. Modyfikacja termiczna drewna poprawia niektóre jego właściwości i walory estetyczne. Większość dostępnego na rynku drewna modyfikowanego termicznie to gatunki drewna krajowego liściastego i iglastego w tym
świerkowego. Drewno termicznie modyfikowane jest ciekawą alternatywą dla gatunków drewna egzotycznego. Modyfikacja struktury drewna wpływa na poprawę
jego niektórych właściwości fizyko-mechanicznych, w szczególności stabilności
wymiarowej, odporność biologiczną (głównie poprzez zwiększenie odporności na
szkodliwe oddziaływanie grzybów) oraz higroskopijność jego struktury [Mazela
i in. 2004; Kartal i in. 2008]. Modyfikacja termiczna poprzez zmniejszenie higroskopijności struktury ma również znaczenie dla poziomu pochłanianej przez
drewno wilgotności [Obataya i in. 2000]. Poprawa tej właściwości następuje w
wyniku zmian składu chemicznego drewna, głównie w wyniku degradacji hemicelulozy [Gunduz, Aydemir, Karakas 2009]. Proces termicznej modyfikacji
drewna prowadzi się zazwyczaj w zakresie temperatur od 160 do 280ºC [Fengel,
Wegener 1989]. Czas ekspozycji drewna zależy m.in. od wielkości elementów
poddawanych modyfikacji termicznej oraz ich wilgotności i wynosi od 15 minut do 24 godzin. Wiadomo, że termiczna modyfikacja drewna prowadzona w
niektórych przypadkach oraz przy pewnych określonych temperaturach i czasach
ekspozycji może powodować spadek wytrzymałości doraźnej drewna.
Drewno jest materiałem palnym, podlegającym termicznej degradacji.
W warunkach pożaru konstrukcja drewniana jest jednocześnie poddana oddziaływaniu wymuszeń w formie sił oraz oddziaływaniom termicznym. Jednoczesne
oddziaływanie tych dwóch czynników wpływa na rozkład naprężeń w strukturze
drewna oraz ogranicza nośność konstrukcji. Wysokie temperatury pożaru powodują dekohezję struktury, a zauważalna redukcja wytrzymałości drewna następuje
w temperaturach większych od 65ºC [Bednarek, Kaliszuk-Wietecka 2004; Bednarek, Ogrodnik, Pieniak 2010]. Na poziomie strukturalnym degradacja wysuszonej
celulozy następuje w temperaturze około 300ºC, jednakże degradacja hemicelulozy następuje już w zakresie temperatur od 150 do 200ºC. Dekompozycja ligniny, stanowiącej o spoistości struktury drewna następuje w zakresie temperatur
pomiędzy 220 a 250ºC [Kamdem, Pizzi, Jermannaud 2002]. Ustalono również,
że dehydratacja ligniny następuje w temperaturze 200ºC.
Celem badań jest określenie wytrzymałości drewna świerkowego modyfikowanego i niemodyfikowanego termicznie w symulowanych warunkach termicznych pożaru, w zakresie poniżej temperatury zapłonu drewna, przy jednoczesnej
realizacji obciążenia statycznego.
Badanie spadku wytrzymałości drewna świerkowego modyfikowanego termicznie ...
99
Materiał i metoda
Badany materiał
Badaniu poddano drewno świerkowe. Próbki wykorzystane w badaniach wytrzymałościowych przedstawiono na rys. 1.
Rys. 1. Próbki drewna modyfikowanego TT (ciemniejsze) i niemodyfikowanego termicznie NTT (jaśniejsze): TS - próbki do badania wytrzymałości na rozciąganie, BS
- próbki zginane, CS - próbki ściskane
Fig. 1. Samples of thermally modified timber TT (darker) and non-modified timber NTT
(lighter): TS – samples for tensile strength tests, BS – samples for bending strength tests,
CS – samples for compression strength tests
Termiczną modyfikację drewna przeprowadzono trzyfazowo (rys.2). Faza
pierwsza - wstępnego ogrzewania - polegała na nagrzaniu suszarki i załadunku
próbek, doprowadzeniu temperatury do 100°C. Przewidziany czas operacji wynosił około 30 min. Następnie stopniowo podnoszono temperaturę do 120°C przez
60 min. W tym czasie następował proces suszenia drewna, którego wilgotność
spadła prawie do zera.
Rys. 2. Proces modyfikacji termicznej drewna [opracowanie własne]
Fig. 2. Timber thermal modification process [own study]
100
Faza druga - intensywnego nagrzewania - miała zasadniczy wpływ na efekt
finalny modyfikacji. Polegała na podniesieniu temperatury do 160°C w ciągu
20 min i przetrzymaniu próbek w tej temperaturze około 6 godzin.
Faza trzecia - schładzania i klimatyzacji - obejmowała obniżenie temperatury
w suszarce do 80-90°C w czasie 60 min. Po tej operacji próbki były pakowane
w folię aluminiową.
Badanie wytrzymałości
Badania wytrzymałościowe wykonano na uniwersalnej maszynie wytrzymałościowej FPZ 100/1 (VEB Thuringer Industriewerk Rauenstein, Germany), która
umożliwia obciążenie siłą statyczną oraz utrzymanie jej w układzie pionowym
na stałym, założonym poziomie. Maksymalna, wytwarzana przez maszynę siła
statyczna wynosi 100kN. Maszyna posiada cztery zakresy prędkości przesuwu
trawersy. W czasie badań zastosowano zakres prędkości I/III, pozwalający na
przesuw trawersy z prędkością 0,021÷0,84 mm/min.
Do obliczenia wytrzymałości na zginanie wykorzystano równanie
(1)
gdzie: Pmax – siła niszcząca próbkę [N],
l – długość próbki [mm],
b – szerokość próbki [mm],
h – wysokość próbki [mm].
Wytrzymałość na rozciąganie obliczono na podstawie równania:
(2)
A – przekrój próbki [mm2].
Wytrzymałość na ściskanie obliczono na podstawie równania:
(3)
A – przekrój próbki [mm2].
101
Symulacja temperatur pożarowych
Przed rozpoczęciem badań wytrzymałości przeprowadzono badania wstępne,
w których ustalono zakresy temperatur eksperymentu oraz określono czasy ekspozycji próbek do momentu wyrównania temperatury w całej objętości próbki.
W badaniach wstępnych w próbkach wykonywano otwór, w którym umieszczano termoparę, w celu dokonania pomiaru temperatur w geometrycznym środku
próbki. Czas nagrzewania określono jako czas, po którym termoparą umieszczoną
wewnątrz próbki zmierzono temperaturę przyjętą w planie badań.
Jako wyjściową przyjęto temperaturę otoczenia równą 20°C. Temperaturę
graniczną określono na poziomie 230°C. Jest to temperatura bliska temperaturze
zapłonu powierzchni drewna. Dodatkowe badania przeprowadzono dla następujących temperatur: 50°C, 100°C oraz 150°C.
W badaniach podstawowych dokonano pomiaru temperatur na powierzchni
próbki za pomocą dwóch termopar rozmieszczonych stycznie do powierzchni
bocznych próbki (rys. 3b). Obciążenie próbki następowało po osiągnięciu założonej temperatury i utrzymaniu jej przez czas ustalony podczas badań wstępnych.
W czasie rzeczywistym rejestrowano wartości sił niszczących oraz temperaturę.
Wzrost temperatury w komorze podczas badania uzyskano przez zastosowanie
urządzenia umożliwiającego nawiew gorącego powietrza (GHG 650 LCE, Bosch,
Germany). Zakres temperatur uzyskiwanych u wylotu dyszy wynosił 50-560°C,
a strumień gorącego powietrza można było regulować w zakresie 250-500 l/min.
Wyniki badań
Wyniki badań wytrzymałości resztkowych w temperaturach pożarowych
Badanie w każdym z elementarnych przypadków obciążenia przeprowadzono na
42 próbkach z drewna niepoddanego modyfikacji termicznej (NTT) i na 42 poddanych modyfikacji termicznej (TT), po 7 próbek w każdym przedziale temperatury.
Fotografie próbek poddanych badaniom wytrzymałościowym w podwyższonych
temperaturach przedstawiono na rys. 3.
Parametry statystyczne uzyskanych wyników badań wytrzymałości na zginanie przedstawiono w tabeli 1, wyników badań wytrzymałości na rozciąganie
w tabeli 2.
102
Rys. 3. Próbki po próbach wytrzymałości w temperaturach pożarowych: TT – drewno modyfikowane termicznie, NTT – drewno nie poddane modyfikacji termicznej,
CS – próbki poddane próbie ściskania, TS – próbki poddane próbie rozciągania, BS
– próbki poddane próbie zginania
Fig. 3. The samples after tests for strength under fire temperatures: TT – thermally modified
timber, NTT – non-modified timber, CS – samples after compression strength test, TS – samples after tensile strength test, BS – samples after bending strength test
Tabela 1. Wyniki badań wytrzymałości na zginanie
Table 1. The results of bending strength tests
Temperatura
[ºC]
Temperature
[ºC]
Wytrzymałość na zginanie Rbw [MPa]
Liczba
próbek
Number
of samples
Bending strength Rbw [MPa]
Odchylenie
standardowe
Odchylenie
standardowe %
85,50
74,25
60,75
83,25
42,75
38,25
5,33
4,86
5,42
15,91
3,54
4,05
6,69
7,20
10,10
32,14
9,18
12,23
96,75
92,25
76,50
72,00
67,50
56,25
4,93
3,03
3,11
3,54
3,99
4,31
5,50
3,46
4,27
5,27
6,53
8,33
Średnia Minimum Maksimum
Average Minimum
20NTT
50NTT
100NTT
150NTT
200NTT
230NTT
7
7
7
7
7
7
79,71
67,50
53,68
49,50
38,57
33,11
72,00
60,75
45,00
38,25
33,75
27,00
20TT
50TT
100TT
150TT
200TT
230TT
7
7
7
7
7
7
89,68
87,43
72,64
67,18
61,07
51,75
83,25
83,25
67,50
63,00
56,25
45,00
Maximum
NTT
TT
Standard
deviation
TT – drewno modyfikowane termicznie; TT – thermally modified timber
NTT – drewno niepoddane modyfikacji termicznej; NTT – non-modified timber
Standard
deviation %
103
Tabela 2. Wyniki badań wytrzymałości na rozciąganie
Table 2. The results of tensile strength tests
Wytrzymałość na rozciąganie Rrw [MPa]
Tensile strength Rrw [MPa]
Temperatura
[ºC]
Temperature Liczba próbek Średnia Minimum Maksimum
Number
[ºC]
Average Minimum Maximum
of samples
NTT
Odchylenie
standardowe
Odchylenie
standardowe %
Standard
deviation
Standard
deviation %
20NTT
50NTT
100NTT
150NTT
200NTT
230NTT
7
7
7
7
7
7
93,86
80,64
46,71
44,00
34,29
21,43
78,00
61,50
34,00
32,00
19,00
5,00
108,00
102,00
56,00
59,00
47,00
32,00
9,97
15,56
8,52
10,02
10,31
8,45
10,63
19,29
18,24
22,77
30,06
39,42
20TT
50TT
100TT
150TT
200TT
230TT
7
7
7
7
7
7
65,00
38,00
21,71
21,36
17,00
8,14
55,00
26,00
7,00
11,00
4,00
1,00
81,00
48,00
34,00
34,00
27,00
14,00
8,87
8,27
8,94
10,20
8,70
4,67
13,65
21,75
41,17
47,76
51,17
57,35
TT
Tabela 3. Wyniki badań wytrzymałości na ściskanie
Table 3. The results of compression strength tests
Wytrzymałość na ściskanie Rcw [MPa]
Compression strength Rcw [MPa]
Temperatura
[ºC]
Odchylenie
standardowe
Odchylenie
standardowe %
39,00
53,25
37,75
29,25
31,50
28,00
4,81
4,43
5,59
3,71
4,07
3,49
14,64
9,20
21,22
14,67
14,99
14,03
66,50
56,00
6,18
4,63
10,29
9,35
Number
[ºC]
of samples
20NTT
50NTT
100NTT
150NTT
200NTT
230NTT
7
7
7
7
7
7
32,86
48,14
26,32
25,25
27,18
24,86
20TT
50TT
7
7
60,11
49,50
NTT
25,50
41,50
22,00
19,00
21,50
19,75
TT
51,75
41,50
Standard
deviation
Standard
deviation %
104
Table 3. Continued
Wytrzymałość na ściskanie Rcw [MPa]
Compression strength Rcw [MPa]
Temperatura
[ºC]
Number
[ºC]
of samples
100TT
150TT
200TT
230TT
7
7
7
7
44,11
41,39
26,25
23,18
38,00
38,00
21,00
18,25
52,50
45,75
33,25
29,00
Odchylenie
standardowe
Odchylenie
standardowe %
5,46
2,76
4,21
4,06
12,38
6,68
16,04
17,50
Standard
deviation
Standard
deviation %
Graficzne miary zmienności rozkładów statystycznych wyników pomiarów
wytrzymałości w kolejnych przedziałach temperatury, ich poziomy i rozrzut statystyczny przedstawiono na wykresach (rys. 4, 5 i 6). Punkty na wykresach określają wartości średnie wytrzymałości, ramki określają poziomy ufności (95%),
natomiast tzw. „wąsy” określają odchylenia standardowe.
Rys. 4. Wyniki badań wytrzymałości na zginanie
Fig. 4. The results of bending strength tests
Rys. 5. Wyniki badań wytrzymałości na rozciąganie
Fig. 5. The results of tensile strength tests
Rys. 6. Wyniki badań wytrzymałości na ściskanie
Fig. 6. The results of compression strength tests
105
106
Intensywność spadku wytrzymałości w warunkach temperatur pożarowych
Intensywność spadku wytrzymałości drewna w wyniku ekspozycji w wysokich
temperaturach określono na podstawie poniższego równania:
(4)
gdzie: Rbw – wytrzymałość na zginanie [MPa],
Rrw – wytrzymałość na rozciąganie [MPa],
Rcw – wytrzymałość na ściskanie [MPa],
T – temperatura [ºC].
Rys. 7. Intensywność zmian wytrzymałości w zależności od temperatury
Fig. 7. The intensity of changes in strength depending on the temperature
Podsumowanie i wnioski
W badaniach oceniano wpływ temperatur pożarowych na wytrzymałość drewna
świerkowego modyfikowanego termicznie w celu wnioskowania o możliwości
wykorzystania tego materiału w konstrukcjach inżynierskich. Oceniano wpływ
modyfikacji termicznej poprzedzającej ekspozycję w podwyższonych temperaturach symulujących temperatury pożaru, co pozwoliło na sformułowanie następujących wniosków:
107
1. Wpływ temperatur pożarowych na spadek wytrzymałości jest jednoznaczny.
W przypadku drewna świerkowego poddanego modyfikacji termicznej (TT)
spadek wytrzymałości na zginanie w temperaturze 230ºC wynosił 42%, natomiast w przypadku drewna niepoddanego modyfikacji termicznej (NTT) 58%
w odniesieniu do uzyskanej w temperaturze 20ºC.
2. W badaniach wykazano istotny wpływ wysokich temperatur na spadek wytrzymałości drewna świerkowego modyfikowanego (TT) i niemodyfikowanego (NTT) termicznie.
3. Odchylenia standardowe wyników pomiarów wytrzymałości drewna TT są
znacząco mniejsze od odchyleń wyników wytrzymałości drewna NTT.
4. W przypadku próbek poddanych obciążeniom zginającym obserwowano
mniejszą wytrzymałość drewna NTT we wszystkich zakresach temperatury,
jednakże wytrzymałości na zginanie drewna TT i NTT w temperaturze normalnej (20ºC) były zbliżone.
5. W próbie rozciągania, obserwowano mniejszą wytrzymałość drewna TT we
wszystkich przedziałach temperatury. Odchylenia standardowe wyników wytrzymałości na rozciąganie są bardzo duże, szczególnie duże w przypadku
drewna TT. Odchylenia wzrastają znacząco w kolejnych zakresach temperaturowych, świadczy to o większej losowości wytrzymałości.
6. Różnice pomiędzy wytrzymałością na zginanie drewna TT i NTT o wysokim
poziomie istotności statystycznej potwierdzają również wyniki testu Scheffe.
Wykazano istotne różnice wytrzymałości drewna TT we wszystkich grupach
determinowanych temperaturą ekspozycji w stosunku do odpowiedników wyników dla drewna NTT
Literatura
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International Communications in Heat and Mass Transfer [37]: 21–28
THE INVESTIGATION OF IMMEDIATE STRENGTH LOSS
OF THERMALLY MODIFIED SPRUCE TIMBER UNDER FIRE
TEMPERATURES
Summary
Thermal modification of timber is one of the new technologies aiming at the improvement
of timber properties. Thermally modified timber (TT) has different aesthetic and utility
parameters compared to non-modified timber (NTT). The objective of this study was the
assessment of the influence of temperatures present in fire conditions on the immediate
changes in strength of thermally modified spruce timber. Tests were made at a dedicated
test stand equipped with a possibility of producing impact with high temperatures. The
values of tensile strength, compression strength and bending strength in normal and fire
temperatures conditions were determined. This paper presents a comparative analysis of
the strength loss of TT spruce timber and NTT spruce timber. The study confirmed a significant influence of fire temperatures on the strength loss of tested timber in chosen ranges
of increasing temperatures.
Keywords: fire temperatures, thermally modified timber, non-modified timber, spruce timber, tensile strength, compression strength, bending strength
Inokentijs Lipinskis, Uldis Spulle1
RESEARCH ON MECHANICAL PROPERTIES OF BIRCH
PLYWOOD WITH SPECIAL VENEER LAY-UP SCHEMES
Plywood is a wood-based panel material laminated of veneers where the grain direction is perpendicular in adjacent layers. The use of plywood can be extended if
there is a possibility to use special lay-up schemes designed to improve mechanical
properties which depend on the grain direction in the outer plies. This report contains results of research whose purpose was to determinate bending strength and
modulus of elasticity of birch plywood types with special veneer lay-up schemes
and of different width, bending flatwise and edgewise. Two special plywood types,
28 mm thick Spec1 and 30 mm thick Spec3, with different veneer lay-up schemes
were selected for bending properties determination tests according to standard EN
789. Specimens were tested when the face veneer direction was parallel and then
perpendicular to the specimens’ longer axis. Moisture content and density were
determined as well. This report contains the comparison of bending strength properties of special plywood specimen with different width and load direction. It was
found that bending strength was significantly higher for narrower special plywood
specimens, and bending strength of special plywood loaded edgewise was 4 % lower for Spec1 and 9.5 % lower for Spec3 than for flatwise loaded specimen of the
same cross-sectional dimensions.
Keywords: birch plywood, veneer lay-up scheme, bending strength, edgewise load
Introduction
The plywood manufacturing industry is one of the most significant industries in
the wood processing sector in Latvia. More than 90% of produced plywood is
exported. In the first half of 2010 the plywood value in the forestry sector exports
amounted to 9.5%. The biggest plywood manufacturer in Latvia is Latvijas Finieris Company, which in a period of crisis tries to increase its turnover by developing specific products with higher added value.
The main products of Latvijas Finieris Company are Riga Ply and plywood
with different surface laminations. The plywood is produced with common lay-up
Inokentijs Lipinskis, Latvia University of Agriculture, Jelgava, Latvia
Uldis Spulle, Latvia University of Agriculture, Jelgava, Latvia
110
Inokentijs Lipinskis, Uldis Spulle
scheme that requires one thickness of veneers which are arranged so that the grain
direction is perpendicular in all adjacent layers. Choosing the default plywood construction causes to size stability in a changing conditions and similar mechanical
properties in both directions - parallel and perpendicular to the longitude. This
applies more to plywood of the thickness over 18 mm that is relatively more homogenous. The thinner the plywood is, the bigger differences in mechanical properties
between plywood of the same thickness and of different face veneer grain direction
appear. Therefore, the face veneer direction defines this material’s suitability.
Proceeding the plywood mechanical properties dependence on veneer layer
orientation, is able to made material with of the required characteristics in any
direction to longitude. Manufacturers designed many plywood types combining
veneers of different thicknesses and made of various wood species [Hrazsky, Kral
2005]. The special plywood types produced in Latvia are composed of similar veneers using special lay-up schemes. Unlike the case of Riga Ply type, mechanical
properties of special construction plywood are less studied.
Plywood as a wood material is heterogeneous, so it can be assumed that the
plywood specimen’s strength is mostly related to veneer natural flaws, e.g. knots.
It is obvious that the larger the specimen area under load is, the greater the probability of occurrence of knot or other flaw is, but the resulting strength values are applied to whole specimen. The standard methods for panel material bending strength
properties determination require specimens of the width of 300 mm, but the used
plywood details often are narrower. The use of special plywood can be extended if
there is a possibility to use plywood for products of small cross-sectional dimensions or to use waste material from plywood processing (mostly cut-offs). Hence,
the dependence of strength properties on specimen’s width should be studied.
There are other possibilities to extend the application of special plywood. For
example, special construction plywood as a material is similar to laminated veneer lumber (LVL), which is designed for use edgewise. Therefore, research on the
strength properties of edgewise loaded special plywood should be useful as well.
The purpose of this report is to test birch plywood types with special veneer
lay-up schemes and compare values of bending strength and modulus of elasticity
determined for plywood species of different widths and at bending flatwise and
edgewise.
Plywood manufacture
The production process of special construction plywood in Latvijas Finieris Company’s plywood mills is the same as Riga Ply production process, except the lay-up stage. The plywood is made of birch (betula sp.) rotary cut veneers of the
thickness of 1.45 mm after drying. The plywood is laminated with phenol-formaldehyde glue. The glue is mixed using resin SFŽ-3014 and mixture Prefere 24J688
111
Research on mechanical properties of birch plywood with special veneer lay-up schemes
containing resin polymerisation accelerator and filler-plasticiser. Lamination parameters are:
–– glue spread rate 180 g·m-2,
–– press temperature 150 oC,
–– press pressure 2.0 MPa,
–– full pressure time is equal to 360 s + 30 s per 1 mm of panel thickness,
–– pressure decreasing time 120 s.
The veneer lamination quality belongs to the 3. class according to EN 314-1
and EN 314-2 standards. The bonding quality of special construction plywood is
not influenced by glue seams of plies of the same grain direction, because glue
seams of perpendicular plies are much weaker.
Then panels are sanded. The thickness of the face veneers is 0.9±0.1 mm. The
panel surface foiled with phenol-formaldehyde film of the density of 120 g·m-2.
One face of the panel is smooth (side F) and the other has wire mesh pattern (side
W). The pattern on side W is used to increase the abrasion resistance of the surface.
Mechanical properties were determined for two types of special plywood:
Spec1 and Spec3. Both types were special constructions. Their veneer lay-up
schemes are given in table 1. The face veneers of both plywood types were WGE
grade. In Spec1 and Spec3 three and four of the outer plies parallel to the panel’s
longer axis, respectively, were BB grade. The adjusted perpendicular outer plies
were WG grade. BB and WG grades are equal to III and IV grade, respectively,
according to EN 635-2 standard. WGE are special WG grade veneers prepared
for foiling, in which all splits, knot holes, picks, imprints and holes are repaired.
Table 1. Veneer lay-up schemes and dimensions of specimens
Tabela 1. Systemy układu fornirów i wymiary próbek
Plywood Number
type of layers
Rodzaj
sklejki
Liczba
warstw
Veneer lay-up scheme*
System układu fornirów
Testing direction
Kierunek badania
flatwise
płasko
Spec1
20
_|||_|_|_||_|_|_|||_
flatwise
płasko
edgewise
bokiem
flatwise
Spec3
22
||_|||_|_|_||_|_|||_||
płasko
edgewise
bokiem
Height or
thickness, mm
Width,
mm
Wysokość lub
grubość, mm
Szerokość,
mm
28
50
28
200
50
28
30
50
50
30
* | - veneer of the grain direction parallel to the longer axis; _ - veneer of the grain direction perpendicular to the longer axis
* | - fornir o orientacji włókien równoległej do dłuższej osi; _ - fornir o orientacji włókien prostopadłej
do dłuższej osi
112
Test methods
The specimens were taken from separate panels. Panels of both plywood types
were selected from one batch. Ten specimens were selected for every specimen
group. The dimensions of the specimens were determined according to EN 325
standard.
Static bending strength and modulus of elasticity at bending values were determined according to EN 789 standard. This method is based on 4-point load of
specimen which involves constant bending moment without shear stress influence
in a specimen failure zone. The bending strength test primary scheme is presented
in fig. 1. To determine the above-mentioned values a testing machine Zwick Z100/
TLS3 was used.
Fig. 1. Bending strength test primary scheme:
l – distance between supports; l2 – distance between point of load and support; F –
load
Rys. 1 Podstawowy schemat testu wytrzymałości na zginanie:
l – odległość między podporami; l2 – odległość między punktem obciążenia a podporą; F –
obciążenie
For bending flatwise half of the specimens in every group were tested with
side F upwards, the other specimens were tested with side W upwards.
Specimen conditioning was conducted according to EN 789 standard. Moisture content and density were determined for all specimens. Moisture content was
determined using weighing method according to EN 322 standard and density was
determined according to EN 323 standard.
Descriptive values were calculated using the method described in EN 326-1
standard. The compared parameters were checked for significance of value difference according to EN 326-2 standard. For comparison of bending strength values
for edgewise tested plywood and LVL, the specimens’ height factor was taken into
consideration according to EN 14374 standard.
113
Mechanical properties comparison
The results of determination of moisture content and density values for the specimens are given in table 2 and 3. The significance of the difference in moisture content values and density values was checked for all specimen groups. No significant
difference in moisture content and density values between any of the compared
specimen groups at 95% probability level (t-test with p < 0.05) was observed.
Table 2. Physical and mechanical properties of Spec1 and Spec3 plywood specimen
tested flatwise
Tabela 2. Właściwości fizyczne i mechaniczne próbek sklejki Spec1 i Spec3badanych na płasko
Bending strength Modulus of elasticity
Statistical value
Wartość statystyczna
Wytrzymałość na
zginanie
fm, N·mm
-2
┴
*
||**
Moduł sprężystości
podłużnej
Moisture content
Density
W, %
ρ, kg·m-3
Wilgotność
E, N·mm
-2
┴
||
┴
||
50 mm wide Spec1
Gęstość
┴
||
Spec1 szerokość 50 mm
Mean value
Średnia
86.3
38.0
10 899
5 575
9.0
8.0
745 712
Odchylenie standardowe
Standard deviation
3.4
6.1
141
545
0.2
0.2
13
18
3.9 % 16.2 %
1.3 %
9.8 %
1.7
%
2.6
%
81.0
10 710
5134
Variation coefficient, %
Współczynnik zmienności, %
5% quantile
kwantyl 5%
30.0
2.2 % 2.7 %
-
-
-
-
200 mm wide Spec1
Mean value
Średnia
68.3
-
10 881
-
9.4
-
-
-
Standard deviation
5.7
-
780
-
1.4
-
-
-
8.3 %
-
6.4 %
-
15.2 %
-
-
-
5% quantile
kwantyl 5%
61.2
-
9 846
-
-
-
-
-
50 mm wide Spec3
Mean value
Średnia
33.4
85.7
4 101
11 726
8.6
7.9
718 707
Standard deviation
4.4
8.0
474
595
0.3
0.2
17
14
11.6 %
5.1 %
2.4
%
2.0
%
3 397
11 056
-
-
5% quantile
kwantyl 5%
13.2 % 9.3 %
27.1
77.5
4.0 % 2.2 %
-
-
114
Table 2. Continued
300 mm wide Spec1***
Spec1 szerokość 300 mm***
Mean value
Średnia
29.6
63.7
5 685
10 930
-
-
-
-
Standard deviation
7.7
11.7
1 194
1 594
-
-
-
-
300 mm wide Spec3***
Spec3 szerokość 300 mm***
Mean value
67.6
22.8
11 836
4 095
-
-
-
-
Standard deviation
13
6
1 828
721
-
-
-
-
Średnia
* ┴ – face veneer of perpendicular grain direction; ** || – face veneer of parallel grain direction
* ┴ – okleina o prostopadłej orientacji włókien; ** || – okleina o równoległej orientacji włókien
*** Zudrags, Ludvigsone-Rudzite 2008
Table 2 presents the results of statistical processing of data obtained for flatwise tested Spec1 and Spec3 plywood.
The results of flatwise tests of Spec1 and Spec3 plywood of the widths of 50
and 200 mm are discussed together with another research results for 300 mm wide
specimen [Zudrags, Ludvigsone-Rudzite 2008]. In every tested group the bending
strength value for 50 mm wide specimen was higher than the bending strength
value for wider specimens.
The mean value of bending strength determined for 50 mm wide Spec1 plywood specimens with perpendicular face veneer grain direction was 86.3 N·mm-2,
which was 26 and 38% higher than the mean values for specimens of the widths
of 200 and 300 mm, respectively.
The mean value of bending strength for 50 mm wide Spec1 plywood specimens with parallel face veneer grain direction was 38 N·mm-2, which was 35%
higher than that value for specimens of the width of 300 mm.
The mean value of bending strength determined for 50 mm wide Spec3 specimens with parallel face veneer grain direction was 85.7 N·mm-2, which was 25%
higher than that value for specimens of the width of 300 mm.
The mean value of bending strength for 50 mm wide Spec3 specimens with
perpendicular face veneer grain direction was 33.4 N·mm-2, which was 44% higher than that value for specimens of the width of 300 mm.
The difference in the mean values of modulus of elasticity at bending determined for each previously compared Spec1 and Spec3 plywood specimen groups
was insignificant.
115
Table 3. Physical and mechanical properties of Spec1 and Spec3 plywood specimen tested
edgewise
Tabela 3. Właściwości fizyczne i mechaniczne próbek sklejki Spec1 i Spec3 badanych bokiem
Bending strength Modulus of elasticity
Wytrzymałość na
zginanie
Statistical value
Wartość statystyczna
fm, N·mm
-2
Moduł sprężystości
podłużnej
Moisture content Density
Wilgotność
E, N·mm
-2
W, %
Gęstość
ρ, kg·m-3
Spec1 with face veneer of perpendicular grain direction
Spec1 z okleiną o prostopadłej orientacji włókien
Mean value
Średnia
Standard deviation
5% quantile
kwantyl 5%
Standard deviation
5% quantile
kwantyl 5%
741
4.1
362
0.3
15
5.0 %
3.4 %
3.8 %
2%
77.2
10 108
-
-
42.8
6 431
8.6
733
2.7
216
0.2
8
6.2 %
3.4 %
2.0 %
1.1 %
39.4
6 127
-
-
Spec3 with face veneer of parallel grain direction
Spec3 z okleiną o równoległej orientacji włókien
Mean value
Średnia
Standard deviation
5% quantile
77.6
10 199
9.1
-
5.9
783
0.5
-
7.6 %
7.7 %
5.1 %
-
69
9 437
-
-
Spec3 with face veneer of perpendicular grain direction
Mean value
Spec3 z okleiną o prostopadłej orientacji włókien
Średnia
Standard deviation
kwantyl 5%
9.0
Spec1 z okleiną o równoległej orientacji włókien
Średnia
5% quantile
10 660
Spec1 with face veneer of parallel grain direction
Mean value
kwantyl 5%
82.7
42.1
6 061
9.0
736
4.1
361
1.0
16
9.7 %
6.0 %
10.8 %
2.2 %
36.6
5 530
-
-
116
Table 3 presents the results of statistical processing of data obtained for edgewise tested Spec1 and Spec3 plywood.
The mean value of bending strength determined for edgewise tested Spec1
plywood specimens with perpendicular face veneer grain direction was 82.7
N·mm-2 and of modulus of elasticity 10660 N·mm-2. Those values were 4 and 2%
lower, respectively, than the values for flatwise tested specimens (table 2).
The mean value of bending strength for edgewise tested Spec1 specimens
with parallel face veneer grain direction was 42.8 N·mm-2 and of modulus of elasticity 6431 N·mm-2. Those values were 13 and 15% higher, respectively, than the
values for flatwise tested specimens.
The mean value of bending strength determined for edgewise tested Spec3
specimens with perpendicular face veneer grain direction was 77.6 N·mm-2 and
of modulus of elasticity 10199 N·mm-2. Those values were 9.5 and 13% lower,
respectively, than the values for flatwise tested specimens (table 2).
The mean value of bending strength for edgewise tested Spec3 specimens
with parallel face veneer grain direction was 42.1 N·mm-2 and of modulus of elasticity 6061 N·mm-2. Those values were 21 and 48% higher, respectively than the
values for flatwise tested specimens.
The comparison of bending properties of tested plywood and 24.3 mm thick
spruce LVL [Ranta-Maunus, Fonselius 2001] revealed that the values of bending
strength for edgewise tested Spec1 plywood, for specimens with perpendicular
and parallel face veneer grain direction, were 47% higher and 24% lower, respectively, than the LVL bending strength value. In the case of Spec3 plywood, for
specimens with parallel and perpendicular face veneer grain direction, the values
of bending strength were 38% higher and 25% lower, respectively, than the LVL
bending strength value. The specimens’ height factor was taken into account in the
comparison. The height factor coefficient used in calculations was kh=1.07.
Summary
The use of the special veneer lay-up scheme is the optimal way to enhance plywood’s mechanical properties in one direction at the expense of decreasing them in
another. This optimisation can be achieved without making any significant changes in technology in mills that produce plywood from veneers of one thickness.
The values of bending strength for both considered special construction plywood types were strongly influenced by the scaling factor. The values were significantly greater for narrower specimens of both types: with most of the layers with
the grain direction parallel or perpendicular to the longer axis.
The values of modulus of elasticity at bending did not depend on the specimen’s width for Spec1 and Spec3 plywood, and the differences in the modulus of
elasticity mean values for separate plywood types were insignificant.
117
The use of the special construction plywood with small cross-sectional dimensions could be beneficial thanks to its mechanical properties values at edgewise
bending which are good enough compared with mechanical properties of the same
material loaded flatwise and with LVL mechanical properties.
References
Hrazsky J., Kral P. [2005]: Assessing the bending strength and modulus of elasticity in bending of exterior foiled plywood in relation to their construction. Journal of Forest Science
[51]: 77–94
Ranta-Maunus A., Fonselius M. [2001]: Timber strength distributions. VTT Research Notes,
Espoo
Zudrags K., Ludvigsone-Rudzite S. [2008]: Bending properties of special lay-up plywood.
Nordic-Baltic Network in Wood Material Science and Engineering, Riga: 114 – 118
List of standards
EN 322. Wood-based panels. Determination of moisture content
EN 323. Wood-based panels. Determination of density
EN 325. Wood-based panels. Determination of dimensions of test pieces
EN 326-1. Wood-based panels. Sampling, cutting and inspection. Sampling and cutting of test
pieces and expression of test results
EN 326-2. Wood-based panels. Sampling, cutting and inspection. Initial type testing and factory production control
EN 789. Timber structures. Test methods. Determination of mechanical properties of wood-based panels
EN 14358. Timber structures. Calculation of characteristic 5-percentile values and acceptance
criteria for a sample
BADANIA WŁAŚCIWOŚCI MECHANICZNYCH
WODOODPORNEJ SKLEJKI BRZOZOWEJ
O ZRÓŻNICOWANYM UKŁADZIE FORNIRÓW
Streszczenie
Zakres stosowania sklejki może być rozszerzony dzięki poprawie jej właściwości mechanicznych, uzyskanej m.in. przez wprowadzenie nietypowych rozwiązań układu fornirów.
Celem badań było określenie właściwości mechanicznych wodoodpornej sklejki brzozowej, okleinowanej błoną fenolową, a różniącej się budową zestawu. Zakres pracy obejmował badania wytrzymałości na zginanie i modułu sprężystości zgodnie z normą EN
789. Pomiary prowadzono wzdłuż i w poprzek włókien dla różnego rozstawu podpór ob-
118
ciążających oraz prostopadle do płaszczyzny sklejki i jej krawędzi. Oznaczono również
wilgotność i gęstość sklejki. Na podstawie przeprowadzonych badań stwierdzono, że wytrzymałość na zginanie jest znacznie wyższa dla mniejszego rozstawu podpór.
Słowa kluczowe:sklejka brzozowa, budowa zestawu, wytrzymałość na zginanie, moduł sprężystości obciążenie
Miloš Hitka, Mária Sirotiakovà1
The impact of economic crisis on THE
change in motivation of furniture company
employees – case study
This work analyses the level of motivation of workers employed in Ekoltech s. r. o.
Fiľakovo in Slovakia in the period till 2008, i.e. before the beginning of economic
crisis, and after the crisis’ start, i.e. at the beginning of 2009. Using Duncan test,
which is a suitable tool for independent choices, the average rates were compared
and significance level p for individual motivational factors was calculated. The
result of this work is definition of significant change in average rates of individual
motivational factors and the comparison of sequence of importance of motivational
factor before and after the crisis. Based on the observations made, it can be said
that the world economic crisis caused change in employee motivation in companies.
The employees were willing to work even in worse conditions, for they wanted to
keep their jobs. Therefore, it was recommended that the management of the analysed enterprise motivate the employees by non-financial motivational factors, which
nowadays are critical to maintain sufficient job performance.
Keywords: motivation, motivational programme, change of motivation, economic
crisis, Duncan test
Introduction
Market globalisation, lack of qualified workforce and financial crisis exert permanent pressure on company management who must pay attention not only to
creation of a competitive strategy, but also to determination and execution of crisis management aimed at company’s survival [Raable 2008]. Any company may
have at its disposal a top-level technology, rich financial resources and scarce
information, but its success and competitiveness depends only on high-quality and
qualified employees. The main goal of human resources management is to attract,
develop, properly utilize, assess, motivate, remunerate, and keep a proper number
Miloš Hitka, Technical University, Zvolen, Slovakia
Mária Sirotiakovà, Institute of Managerial Systems, Poprad, Slovakia
120
Miloš Hitka, Mária Sirotiakovà
of employees at adequate working positions in a company and in this way provide
the company with appropriate workforce [Werther, Davis 1992].
Problem
One of the most important and at the same time the most difficult task of human
resources management is motivation of employees, which is the basis for human
resources management. Without proper level of motivated behaviour and performance of employees it is impossible to determine goals and to meet them as well.
This paper deals with analysis of motivation in the period 2007-2009 in Ekoltech,
s.r.o. Fiľakovo, and the impact of the economic crisis on the change in employees’
motivation. The analysed enterprise is an important producer of furniture for the
distribution network of IKEA Company and it employs more than 800 employees
in the area of Novohrad.
Management in the period of crisis requires the use of non-financial remuneration of employees which can be done in several ways: 1) team rebuilding, 2) organisation of educational activities within the company, 3) training of employees,
4) organisation of requalification courses, language courses, managerial and IT
courses, expert courses, seminars and trainings or 5) using different outsourcing
market tools [Potkány 2008]. Company may also organise sports and other company events aimed at improvement in human relations. The attention should also
be paid to internal communication in the company, especially with subordinates.
Another form of non-financial motivation is regular demonstration of appreciation on the part of supervisor and provision of appreciation, so that employee
gets more responsibility at work. The employer should let the employees select
non-financial benefits. Other form of employees’ motivation is self-realisation,
i.e. delegation of some competencies and duties. Motivation of employees may be
executed even in the change of company management. For some employees benefits and motivational programmes leading to their self-realisation or satisfying
their economic requirements may be effective. From the employer’s perspective,
low-cost tools which help him start utilising the potential hidden in the employees
are effective.
Other forms of motivation in the period of crisis include:
–– change of internal communication – management more often and openly communicate with employees, determines groups of specialists to solve section
problems, create place for non-traditional solutions to proposals and problems, even apart from the official organisational structure of the company,
–– enhancement of work – in the period of crisis, due to redesign of some working positions, some jobs may be downsized and part of their workload can
be transferred to remaining posts,
–– employees’ development – this period of fewer orders may be used for employees’ development and growth, and in such periods the knowledge poten-
The impact of economic crisis on the change in motivation of furniture company employees ...
121
tial “hidden” in the company should be utilised, e.g. lecturers working with
the company,
–– improvements to company processes and their presentation at wide company
forum – this method may also improve team work, if the task is to bring the
offer of individual working teams for the benefit of the whole company,
–– working hours – if possible, flexible working hours may be introduced (such
a possibility is appreciated not only by younger people as it is often believed),
–– free days – employees appreciate an additional free day especially before holidays and they like higher number of general holiday as well,
–– social programme – a “cheaper solution” than an increase in wages or paying
bonuses for higher output or motivational bonuses or extra holiday money or
thirteenth salary is an increase in the value of luncheon vouchers, contribution
to pension and life insurance, equipping company fitness centre, organising
daily camps for employees’ children [Raable 2009].
Experimental part
It is impossible that one motivational factor motivates employees to work perfectly
every day, minimise costs and be reliable. To be able to get answers to questions
like: how employees assess their work positions, how they feel at their work, and
what the structure of their needs is, a repetitive analysis of motivational structure
in a selected group of employees in the period 2007-2009 was carried out. To
this end, a general questionnaire, a survey tool, was developed [Hitka 2009a]. In
the studied case group sampling of employees was carried out and respondents’
answers to the questions concerning satisfaction with motivation factors applied
in the analysed enterprise were discussed. The first part of the questionnaire contained general factual information concerning the respondents’ sex, age, education
and number of years worked in the company. The second part encompassed 30
structured questions about motivational factors. The employees were supposed to
assign a level of importance based on a scale of motivational factor assessment to
each factor. Five options marked by numbers 1-5 (1 – most dissatisfied, 5 – most
satisfied) were provided. The analysis of motivational factors was carried out in
2007, 2008 and 2009. Each year 100 questionnaires were delivered to production
departments. The total return of the questionnaires was 62%, out of which 92 were
answered by men and 94 by women.
Statistical verification by Duncan test, which determines significant rate of
change and rate of importance between motivational factors when individual years
are compared, was done. Based on the questionnaires interpretation, the conflict
between subjective factors and actual situation was illustrated. The interpretation
had the following several phases:
–– calculation of average rates assigned to the requested state of motivation for
a group of analysed employees,
122
–– numerical and graphical illustration of calculated average rates of the requested state of motivation for individual factors of analysed employees,
–– numerical illustration of significant rate of change according to Duncan test.
Based on the questionnaires interpretation, it was summarised that in 2007 and
2008 the most important factors of motivation for employees were: good working
team, financial remuneration, supervisor´s approach, free time, recognition, basic
salary and fair employee’ assessment. In 2009, after the start of the economic
crisis, priorities of the employees’ motivation changed. First positions belonged
to motivators such as job security, basic salary, good working team, recognition,
working process, free time and working environment.
Results
In spite of the fact that a slow increase in average rates is visible when the levels
of motivation in 2007 and 2008 are compared, it can be said that in the analysed
enterprise there was no critical change in motivational factors (p < 0.05).
When average rates of individual motivational factors in 2008 and 2009
(table 1) is analysed, there are relevant changes in 26 out of 30 items (good working team, financial remuneration, communication at place of work, opportunity
to apply own abilities, scope of employment and type of work done, acquaintance with reached working result, working hours, working environment, working
output, working process, competences, supervisor´s approach, individual decision-making, self-realization, social benefits, fair employee´s assessment, stress/
elimination of stress at place of work, psychical effort, company vision, region
development, education and personal growth, relation of the company to the environment, free time, recognition, basic salary). For 12 factors (financial remuneration, opportunity to apply own abilities, scope and type of work done, working
output, supervisor´s approach, social benefits, fair assessment, stress/elimination
of stress at place of work, company vision, region development, recognition, basic
salary) there is zero level of relevance and a critical change of motivation rate can
be seen. The employees were willing to work even when working conditions were
worse.
Based on the actual surveys of stability of motivational moods in companies
[Hitka 2009a, 2009b], it is possible to summarise that in general the level of motivation of employees of production companies remains unchanged in the horizon
of 5-6 years. The results of this analysis indicate that under the world economic
crisis conditions and economic and social effects of the crisis, there was a relevant
change in the level of motivation and employees were motivated by different motivational factors than before the crisis started. The order of motivational factors
was substantially changed as well.
123
Table 1. The comparison of motivation change significance in 2008 and 2009
Tabela 1. Porównanie istotności zmian w motywacji w 2008 i 2009 roku
S. n.
lp.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Motivational factor
Czynnik motywacyjny
Atmosphere at work
Atmosfera w pracy
Good working team
Zgrany zespół współpracowników
Financial remuneration
Wynagrodzenie pieniężne
Job physical effort
Wysiłek fizyczny
Job security
Bezpieczeństwo zatrudnienia
Communication at work
Komunikacja w pracy
Company name
Nazwa przedsiębiorstwa
Opportunity to apply own abilities
Możliwość wykorzystywania własnych zdolności
Scope of employment and type of work done
Zakres obowiązków i rodzaj wykonywanej pracy
Acquaintance with achieved work result
Znajomość osiągniętych wyników pracy
Working hours
Godziny pracy
Working environment
Środowisko pracy
Work output
Wydajność pracy
Working process
Proces pracy
Competences
Kompetencje
Prestige
Prestiż
Supervisor’s approach
Podejście przełożonego
Individual decision-making
Indywidualne podejmowanie decyzji
Self-realisation
Samorealizacja
Social benefits
Korzyści socjalne
Fair assessment of employees
Uczciwa ocena pracowników
Ø
state 2008
Ø
state 2009
p
4.52
4.34
0.114
4.67
4.40
0.021
4.69
4.13
0.000
4.14
3.88
0.103
4.50
4.41
0.572
4.43
4.07
0.011
4.16
4.07
0.612
4.24
3.71
0.000
4.31
3.76
0.000
4.38
3.93
0.003
4.47
3.97
0.001
4.59
4.18
0.001
4.64
4.15
0.000
4.52
4.18
0.021
4.66
3.93
0.011
4.29
3.93
0.037
4.66
4.04
0.000
4.40
4.00
0.006
4.36
3.87
0.001
4.60
3.90
0.000
4.66
4.01
0.000
stan w 2008 stan w 2009
124
Table 1. Continued
22.
Stress/elimination of stress at work
Stres (jego eliminacja) w pracy
Psychical effort
23.
Wysiłek fizyczny
Company vision
24.
Wizja przedsiębiorstwa
Region development
25.
Rozwój regionu
Education and personal growth
26.
27.
Edukacja i rozwój osobisty
Company relation to the environment
Stosunek przedsiębiorstwa do środowiska
Free time
28.
Czas wolny
Recognition
29.
30.
Uznanie
Basic salary
Wynagrodzenie podstawowe
4.45
3.82
0.000
4.26
3.82
0.009
4.57
3.93
0.000
4.55
3.99
0.000
4.36
3.91
0.006
4.38
4.01
0.004
4.64
4.18
0.001
4.74
4.22
0.000
4.91
4.40
0.000
Source: own survey
Źródło: ankieta własna
Managers usually predict that their employees are the most interested in money and they often do not know or do not take into consideration the fact that
there are other motivational factors which are even more important for employees.
Having done this motivation survey aimed at production workers in the analysed
enterprise, it can be summarised that the most important motivational factors are
factors of existence, i.e. job security, basic salary, financial remuneration. The next
area is described by social factors, i.e. good working team, recognition, working
process, communication at place of work, and job factors, i.e. working environment and working output.
Conclusions
Transition from centrally planned economy to free market economy forced most
companies to pay more attention to their employees. The result of this process
is that a lot of top companies worked out motivational programmes and really
respect their employees. The existence of a company, its competitiveness and prosperity depend at first on the quality of its human resources. Apart from effective
way of employees’ recruitment, the quality of human resources and increase in
performance is assured also by existence of various motivational elements. The
system of assessment and remuneration, further education and increase in qualifications, various employee and social benefits and good work organisation,
125
significantly supports the increase in motivation. A set of motivational factors enables the company to utilise the potential of its employees, so the company scores.
The form and intensity of achievement of company’s goals leads to growth of
work productivity, reduction of costs and general satisfaction of employees.
Based on the observations made, it can be said that the Slovak economy was
much influenced by the world economic crisis as well. Not only did it result in
high unemployment, decline in performance and drop in sales but also in a substantial change in employees’ motivation across Slovakia [Hitka, Vacek 2010].
This is the reason why, in the period of overcoming the crisis’ effects, it was
recommended that the management of the analysed enterprise motivate their employees especially with non-financial motivational factors which are critical to
keeping of job performance.
Literature
Hitka M. [2009a]: Model analýzy motivácie zamestnancov výrobných podnikov. Vedecká monografia. ES TU Zvolen. Zvolen
Hitka M. [2009b]: Zhodnotenie výskumu motivácie zamestnancov vo výrobných podnikoch
Slovenska za roky 2000–2008. Medzinárodná vedecká konferencia MĽPvP. Žilina
Hitka M., Vacek V. [2010]: Changes in motivation of workers in production in a production
company as a result of the economic crisis. MVK Human Potential Development: Search
for Opportunities in the New EU States. Mykolas Romeris University, Vilnius, Litva
Potkány M. [2008]: Personnel outsourcing processes. In: Ekonomie a management: vědecký
ekonomický časopis. [11]: 53-62
Werther W. B., Davis K. [1992]: Lidský faktor a personálny manažment. Victoria Publishing,
Praha
Note: The work is a creative output of the grant task VEGA 1/0717/08 System approach to
professional development of human resources aimed especially at knowledge management,
VEGA 1/0360/08 and VEGA 1/0622/2010 Company restructuring process – approaches to and tools
of restructuring process management in wood companies.
WPŁYW KRYZYSU GOSPODARCZEGO NA ZMIANĘ
MOTYWACJI PRACOWNIKÓW ZATRUDNIONYCH W FIRMIE
MEBLARSKIEJ – STUDIUM PRZYPADKU
Streszczenie
W pracy analizowano poziom motywacji pracowników etatowych w firmie EKOLTECH s.r.o. Fil’akovo na Słowacji przed kryzysem ekonomicznym do roku 2008 i po
jego nadejściu na początku roku 2009. Stosując test Duncana, przydatny do niezależnych wyborów, porównano średnie oceny i wyliczono poziom istotności (p) dla indy-
126
widualnych wskaźników motywacyjnych. Wynikiem pracy jest zdefiniowanie istotnej
zmiany średniej oceny indywidualnych wskaźników motywacyjnych i przedstawienie ich
według rangi przed i po kryzysie. Na podstawie naszych obserwacji można stwierdzić,
że światowy kryzys gospodarczy ma także wpływ na zmianę motywacji w firmach. Pracownicy są chętni do pracy nawet w gorszych warunkach, gdyż zależy im na utrzymaniu
pracy. Oto dlaczego zarządowi badanego przedsiębiorstwa zaleca się motywowanie swoich pracowników innymi niż finansowe wskaźnikami motywacyjnymi, pozwalającymi
utrzymać dostateczną wydajność pracy.
Słowa kluczowe:motywacja, program motywacyjny, zmiana motywacji, kryzys gospodarczy, test
Duncana
KOMUNIKATY – ANNOUNCEMENTS
Ewa Ratajczak 1
OSIĄGNIĘCIA INSTYTUTU TECHNOLOGII DREWNA
W OBSZARZE BADAŃ CZWARTORZĘDOWYCH SOLI
AMONIOWYCH
Przedstawiono osiągnięcia badawcze Instytutu Technologii Drewna uwieńczone
uzyskaniem prestiżowej nagrody Ministra Środowiska w 2010 roku za innowacyjne
i nowatorskie prace z zakresu badań czwartorzędowych soli amoniowych.
Słowa kluczowe: nagroda Ministra Środowiska, czwartorzędowe sole amoniowe,
ciecze jonowe
Wskutek wyeliminowania z rynku klasycznych środków ochrony drewna zawierających skuteczne biocydy w postaci polifenoli, pentachlorofenolu, chloronaftalenów, fluorków, fluorokrzemianów, podjęto w Instytucie Technologii Drewna
intensywne prace badawcze dotyczące zastosowania czwartorzędowych związków amoniowych w środkach ochronnych, które były aplikowane wcześniej jako
preparaty dezynfekcyjne. Ta nowa grupa substancji biologicznie czynnych, biodegradowalnych w środowisku, szczególnie chlorek didecylodimetyloamoniowy,
chlorki alkilobenzylodimetyloamoniowe, chlorki cocotrimetyloamoniowe, propionian i boran didecylometylopoli(oxyetylo)amoniowy, wykazała skuteczność
wobec Basidiomycotina, porównywalną z preparatami chromowo-miedziowo-arsenowymi. Wkrótce znalazły one powszechne zastosowanie w recepturach środków do ochrony drewna użytkowanego na zewnątrz, bez kontaktu z gruntem.
W Instytucie Technologii Drewna, w latach dziewięćdziesiątych ubiegłego
stulecia, w wyniku realizacji prac badawczych został opracowany i wdrożony
w zakładach przemysłu drzewnego preparat Fungosept, na bazie komercyjnych
czwartorzędowych soli amonowych, do zabezpieczana surowca drzewnego przed
grzybami sinizny. Ten przełom sprawił, że kolejne badania ukierunkowane zostaEwa Ratajczak, Instytut Technologii Drewna, Poznań, Polska
128
Ewa Ratajczak
ły na pogłębienie wiedzy w zakresie możliwości syntetycznych nowych struktur
chemicznych czwartorzędowych związków amoniowych, oddziaływania ich na
zbiorowiska grzybów niszczących materiał lignocelulozowy, interakcje z drewnem, jak również badania skutków dla środowiska przez te nowe związki biologicznie czynne, ich oddziaływania z abiotycznymi komponentami środowiska.
Dzięki wymianie w strukturze czwartorzędowych soli amoniowych anionu halogenowego na inny anion nieorganiczny lub organiczny, uzyskano związki chemiczne przyjazne środowisku, o nowych właściwościach fizykochemicznych,
wielofunkcyjnym działaniu, będące cieczami w temperaturze do 100 oC. Z uwagi
na charakter jonowy nazwano je „cieczami jonowymi” (ILs), jak również „związkami przyjaznymi środowisku” z powodu ich łatwego recyklingu oraz niskiej
prężności par. Ciecze jonowe stanowią alternatywę dla lotnych i toksycznych
rozpuszczalników organicznych, ale jak się wkrótce również okazało, znalazły
zastosowanie w wielu dziedzinach gospodarki z uwagi na swą wielofunkcyjność.
W wyniku kilkuletnich badań opracowano, wspólnie z zespołem prof. dr. hab.
J. Pernaka z Wydziału Technologii Chemicznej Politechniki Poznańskiej, powierzchniowo czynne związki organiczne o budowie jonowej - dimeryczne sole
amoniowe, zwane solami „gemini” , o swoistym działaniu biologicznym, tj. skuteczne wobec grzybów wyższych niszczących drewno, a zarazem podatne na rozkład
w środowisku wodnym i glebowym przez bakterie i grzyby niedoskonałe. Badania te miały charakter nowatorski, niemający odpowiedników w kraju i za granicą. Charakteryzują się wysokim poziomem naukowym, a wprowadzenie do
praktyki uzyskanych wyników (opracowanie całkowicie nowych fungicydów),
wypełni lukę na rynku środków chemicznych do zabezpieczania drewna przed
zgnilizną, umożliwi zwiększenie trwałości drewna , dzięki czemu powiększy się
baza surowcowa dla drzewnictwa i budownictwa, bez negatywnego oddziaływania na środowisko. Uwieńczone sukcesem prace doświadczalne prof. nadzw.
dr hab. Jadwigi Zabielskiej-Matejuk w obszarze badań proekologicznych związków bioczynnych, przedstawione zostały w monografii pt. „Ochrona drewna
nowej generacji czwartorzędowymi solami amoniowymi” . Pracę tę wyróżniono
w dniu 18 października 2010 roku w Warszawie prestiżową nagrodą Ministra Środowiska za szczególne osiągnięcia naukowo-badawcze, przyznawaną corocznie
w trybie konkursu naukowcom i zespołom badawczym za innowacyjne i nowatorskie dokonania, ukierunkowane na zastosowanie praktyczne, wyróżniające się
efektami naukowymi, gospodarczymi i społecznymi. Rezultaty badań z pogranicza leśnictwa i technologii drewna, prowadzone przez prof. Jadwigę Zabielską-Matejuk, mają niezwykłe znaczenie dla gospodarki, zostaną bowiem wykorzystane przez praktyków sektora leśno-drzewnego, budownictwa, konserwatorów
obiektów muzealnych jak również wdrożone w zakładach przemysłu drzewnego.
Wdrożenie wyników pracy przyczyni się do ochrony gleby, powietrza oraz do
przeciwdziałania zanieczyszczeniom akwenów nieulegającymi bioeliminacji, stosowanymi aktualnie środkami ochrony drewna.
Osiągnięcia instytutu technologii drewna w obszarze badań czwartorzędowych soli amoniowych
129
THE ACHIEVEMENTS OF THE WOOD TECHNOLOGY
INSTITUTE IN THE AREA OF RESEARCH ON QUATERNARY
AMMONIUM SALTS
Summary
The Wood Technology Institute has been conducting research on the use of quaternary ammonium salts in wood protection for over 15 years. New biologically active compounds have been
developed. The paper presents the achievements of the Wood Technology Institute in the field
of research on a new group of biocides easily degradable by micro-flora present in soil and
water. The research results have been published in the dissertation study titled “Wood protection by a new generation of quaternary ammonium salts” of the authorship of associate professor Jadwiga Zabielska-Matejuk. Minister of the Environment awarded this monograph in 2010.
Keywords: Minister of the Environment Award, quaternary ammonium salts, ionic liquids
Dorota Fuczek, Magdalena Czajka1
7. EUROPEJSKIE SYMPOZJUM PŁYT
DREWNOPOCHODNYCH
Tematyka sympozjum obejmowała zagadnienia dotyczące stanu obecnego i perspektyw rozwoju przemysłu płytowego w Europie. Przedstawiono nowe koncepcje
i rozwiązania technologiczne stosowane w produkcji płyt drewnopochodnych. Zaprezentowano wysokiej jakości produkty płytowe wytwarzane m.in. z odnawialnych
surowców, a także płyty o bardzo niskiej emisji formaldehydu.
Słowa kluczowe: panel płyt drewnopochodnych, technologia produkcji, redukcja
emisji formaldehydu, sympozjum
W dniach 13 - 15 października 2010 roku, Hanower już po raz siódmy stał się
miejscem spotkania około 300 przedstawicieli zarówno ośrodków akademickich,
naukowych, jak i przemysłowych z całego świata. Powodem spotkania było odbywające się co dwa lata Europejskie Sympozjum Tworzyw Drzewnych. Wydarzenie to, organizowane przez Fraunhofer Institute for Wood Research (WKI),
International Association for Technical Issues relating to Wood (iVTHe.V.) oraz
European Panel Federation (EPF) uznawane jest za największą europejską konferencje poświęconą problematyce związanej z technologią płyt drewnopochodnych.
Konferencja rozpoczęła się od przedstawienia obecnej sytuacji panującej
na europejskim rynku przemysłu tworzyw drzewnych. Ladisalus Döry, prezydent EPF, w swoim wystąpieniu podkreślił konieczność podejmowania działań
zarówno ekonomicznych, jak i ekologicznych zmierzających do pokonania następstw globalnego kryzysu. Dalszy rozwój przemysłu płyt drewnopochodnych
według Andreasa Michanickl’a (University of Applied Science Rosenheim) powinien opierać się na najnowszych rozwiązaniach technologicznych pozwalających zwiększać wydajność produkcji przy jednoczesnym zmniejszaniu zużycia
surowca i energii. Jaki inny przemysł wykorzystuje odnawialne surowce? Jaki
Dorota Fuczek, Instytut Technologii Drewna, Poznań, Polska
Magdalena Czajka, Instytut Technologii Drewna, Poznań, Polska
132
Dorota Fuczek, Magdalena Czajka
inny przemysł może zamknąć obieg dla swoich produktów tak jak przemysł płyt
drewnopochodnych? Jaki inny przemysł wytwarza energię elektryczną z surowców zrównoważonych dla sieci publicznej? To pytania, a zarazem stwierdzenia
prelegenta z Rosenheim, który w ten sposób podkreślił innowacyjność i dynamiczny rozwój przemysłu płyt drewnopochodnych w kilku ostatnich latach.
W dalszej części spotkania przedstawiono najnowsze rozwiązania technologiczne opracowane dla przemysłu tworzyw drzewnych m.in.: EcoDry – technologie suszenia w zamkniętym obiegu (Schenkman-Piel-Engineering-Swiss Combi),
EVojet – system aplikacji żywicy (Sunds MDF Technologies), CONTI-SOUND
– nowy sposób wykrywania wybuchów. Innowacyjne rozwiązane dla skrawarki
pierścieniowej przedstawił Ricardo Ferrari reprezentujący firmę Globus. Włoska
firma zaprezentowała skrawarkę pierścieniową z ruchomym dyskiem równomiernie rozprowadzającym zrębki w pierścieniu nożowym, co według specjalistów
decyduje nie tylko o wysokiej jakości otrzymywanych wiórów lecz również pozwala uzyskać 90% wydajność skrawania.
Tradycyjnie już, powtarzającym się tematem wielu referatów, były kwestie
związane z emisją i zawartością formaldehydu w płytach. Ten, budzący duże zainteresowanie, blok tematyczny rozpoczął Harald Schwab z WKI przedstawiając
roboczą wersję projektu, w którym proponuje się międzynarodową standaryzację
metod oznaczania emisji formaldehydu z płyt drewnopochodnych. Produkcja płyt
drewnopochodnych o niskiej emisji formaldehydu (CARB faza 2, EPFS, F****)
wymaga często stosowania specjalnych, niestety znacznie droższych, żywic klejowych. Nowe rozwiązania technologiczne i stosowanie alternatywnych dodatków
do żywic klejowych były przedmiotem wystąpień naukowców reprezentujących
różne ośrodki badawcze w Europie. W tym miejscu warto przywołać referaty Georges Francis z Advachem S.A. „Środki wiążące formaldehyd – przegląd
i badania” oraz przedstawicieli WKI (Jan Gunschera, Katrin Bokelmann), którzy
zaprezentowali wyniki badań zastosowania modyfikowanych zeolitów redukujących emisję formaldehydu z płyt drewnopochodnych. Stosowanie dwóch różnych
rodzajów żywic – na warstwę środkową tradycyjnej żywicy mocznikowo-formaldehydowej (UF), na warstwy zewnętrzne klejów bazujących na związkach akrylowych, to rozwiązanie dla płyt wiórowych o niskiej emisji formaldehydu proponowane przez przedstawicieli firmy BASF. Eleftheria Athanassiadou, Charles
Markesini, Sophia Tsiantzi z Chimar Hellas S.A. przekonywali, iż produkcja płyt
cechujących się emisją formaldehydu na poziomie emisji z drewna jest możliwa do osiągnięcia dzięki stosowaniu zaawansowanych technologii syntezy żywic
aminowych.
Uwieńczeniem konferencji było przyjęcie zorganizowane przez firmę Sasol
Wax w jednym z pawilonów EXPO 2000.
7. europejskie sympozjum płyt drewnopochodnych
133
THE 7th EUROPEAN WOOD-BASED PANEL SYMPOSIUM
Summary
On 13-15 October 2010 Hannover was the host city of the 7th European Wood-Based Panel Symposium. That biggest European conference devoted to the technology of wood-based products was a meeting place for around 300 participants representing the academia
and industry. Amongst main topics discussed during the symposium were economic and
ecological challenges, energy concerns, development in production and research, and new
products and their application.
Keywords: wood-based panels, technology, reduction of formaldehyde emission, symposium
Grzegorz Kowaluk1
THE ISSUES OF WOOD PROCESSING
ON THE 7th INTERNATIONAL SCIENCE CONFERENCE
“CHIP AND CHIPLESS WOODWORKING PROCESSES”
The 7th International Science Conference on “Chip and Chipless Woodworking
Processes” was organised on 9-11 September 2010 in Terchova, Slovakia, by the
Department of Woodworking at the Faculty of Wood Sciences and Technology
of the Technical University in Zvolen. The aim of the Conference was to provide
the specialists in science, research and pedagogy with a forum to present and
discuss new knowledge and results in the field of chip and chipless woodworking
processes.
Keywords: woodworking, machining, wood, wood-based material, tool, conference
The rapid progress in woodworking machinery construction as well as in new
and improved wood-based composite materials and modified wood has resulted
in changes of typical methods of wood processing. Those issues were discussed
on the 7th International Science Conference “Chip and Chipless Woodworking
Processes” organised on 9-11 September 2010 in Terchova, Slovakia, by the Department of Woodworking at the Faculty of Wood Sciences and Technology of
the Technical University in Zvolen. The aim of the Conference was to provide the
specialists in science, research and pedagogy with a forum to present and discuss
new knowledge and results in the field of chip and chipless woodworking processes. The conference agenda consisted of 3 main sections:
–– mechanical woodworking,
–– thermal treatment of wood,
–– technical legislation in wood industry.
In the section “Mechanical woodworking” a wide-range of issues concerning technical and technological factors of processes, machine-tool interaction,
as well as physical properties of chips was discussed. Chosen papers from this
section encompassed: 1) “The influence of the parameters of wood based agglomerated materials cutting process by abrasive water-jet on the kerf width”,
Grzegorz Kowaluk, Wood Technology Institute, Poznan, Poland
136
Grzegorz Kowaluk
2) “Popcornboard – chipboard modified with popcorn”, 3) “Working of softwood round timber into structural timber and assessment of their quality”, and 4)
“Computer aided monitoring of indices for economic efficiency in woodworking
enterprises”.
“Thermal treatment of wood” section concerned technical and technological
factors of processes and in that field the following subjects were discussed: 1)
“Assessing the effect of the pressing parameters on the shape stability of water-resistant plywoods”, 2) “Model for calculation of the heat consumption for heating
of pit’s corpus for thermal treatment of wood materials”, and 3) “Potential role of
biomass as a source of renewable energy in the future global energy mix and its
possible impacts on the air quality”.
The section titled “Technical legislation in wood industry” was devoted to
risk, health aspects and safety regulations in wood industry.
In the section “Mechanical woodworking” the following two papers written
by the Wood Technology Institute researchers were presented: “Influence of the
raw materials parameters on the properties of the fibrous chips and particleboards” and “Investigation on drilling of the particleboards produced from fibrous
chips”.
The next 8th Conference will be organised in 2012.
PROBLEMATYKA PRZEROBU DREWNA
NA 7. MIĘDZYNARODOWEJ KONFERENCJI NAUKOWEJ
„CHIP AND CHIPLESS WOODWORKING PROCESSES”
Streszczenie
W dniach 9-11 września 2010 roku w Terchovej (Słowacja) odbyła się 7. Międzynarodowa
Konferencja Naukowa „Chip and Chipless Woodworking Processes”. Organizatorem konferencji była Katedra Obróbki Drewna Wydziału Nauki o Drewnie i Technologii Uniwersytetu Technicznego w Zwoleniu (Słowacja). Celem konferencji była prezentacja
wyników prac naukowych oraz naukowo-badawczych pracowników zajmujących się teoretycznymi, technicznymi oraz technologicznymi problemami procesów wiórowej i bezwiórowej obróbki drewna.
Słowa kluczowe: obróbka drewna, drewno, tworzywa drzewne, narzędzie, konferencja
Władysław Strykowski1
SPRAWOZDANIE Z COROCZNEJ KONFERENCJI
EUROPEJSKIEGO INSTYTUTU LEŚNEGO
Doroczna Konferencja Europejskiego Instytutu Leśnego odbyła się 15 października
2010 roku w Dreźnie. Konferencji towarzyszyło seminarium dotyczące biomasy pochodzącej z lasów i pozostałych obszarów.
Słowa kluczowe: EFI, program, sprawozdanie, badania
Od kilku lat, zgodnie z postanowieniami członków Europejskiego Instytutu Leśnego (EFI), doroczne posiedzenia plenarne organizowane są w krajach członkowskich, zgłaszających wolę ich przeprowadzenia. Ostatnie z nich odbyło się w
Dreźnie 15 października 2010 roku.
Konferencja była jednodniowa, w trakcie której, oprócz programu związanego
głównie z działalnością EFI, Uniwersytet Techniczny w Dreźnie przedstawił
syntezę materiałów pt. „Biomasa z lasów i pozostałych obszarów”. Materiały te
zawierają referaty12omawiające problematykę biomasy w Niemczech, Rosji, Austrii, Włoszech i Szwecji:
–– A. Berman: Biomasa z lasów i pozostałych obszarów. Produkcja i zużycie,
–– H. Roder: Samowystarczalność drewna w Niemczech i w Europie – Stan aktualny i perspektywy,
–– A. Berman i in.: Możliwości i bariery dla drewna krótkich rotacji,
–– U. Kies, D. Herold: Niemiecki Sektor Leśny. Narodowy benchmarking, regionalne klastry i rola inicjatyw sieciowych,
–– V. Petrov, A. Orlov: Energetyczna utylizacja drewna w północno-zachodniej
Rosji,
–– P. Liebhard i in.: Status quo drewna krótkich rotacji i systemy rolno-leśne,
–– G. Picchci, R. Spineli: Techniki i technologie produkcji drewna krótkich rotacji,
–– M. Weich: Status quo drewna krótkich rotacji i systemy rolno-leśne w Szwecji.
Władysław Strykowski, Instytut Technologii Drewna, Poznań, Polska
1
Prezentowane na konferencji materiały wydane przez Federal Ministry of Food,
Agriculture and Consumer Protection są dostępne w Instytucie Technologii Drewna
w Poznaniu.
138
Władysław Strykowski
Roczny raport, który był przedmiotem dyskusji, został przesłany członkom
EFI w czerwcu 2010 roku. Jest on także dostępny na stronach http:/www.efi.int/
portal/virtual library/annual reports. Wyniki badań audytorskich potwierdziły prawidłowe działanie EFI w roku objętym audytem.
W raporcie w sposób syntetyczny określono strategię działania EFI do 2025
roku. Misją EFI jest wzmacnianie i mobilizacja europejskich badań leśnych i ekspertyz adresowanych dla potrzeb podmiotów podejmujących decyzje z zakresu
lasów i leśnictwa.
W celu wdrażania misji EFI niezbędne jest:
–– prowadzenie badań i wykonywanie ekspertyz na poziomie paneuropejskim,
–– prowadzenie polityki doradztwa dotyczącego leśnictwa związanego z Europą,
–– ułatwianie i stymulowanie powstania leśnych sieci na poziomie paneuropejskim,
–– wspieranie zapotrzebowania na politykę bezstronności związaną z informacją
w europejskich lasach i leśnictwie,
–– rzecznictwo wspierające badania leśne i naukowe informacje jako podstawy
dla decydentów w zakresie polityki leśnej w Europie.
Głównymi kierunkami badań EFI są:
–– lasy dla wielorakich potrzeb,
–– lasy, klimat i energia,
–– polityka sektora leśnego i zarządzanie,
–– przyszłość lasów i badań.
Ważnym punktem posiedzenia był wybór dwóch członków Rady na okres
2010-2013. Spośród pięciu osób kandydujących do Rady (Aleksander Alekseev,
Peter Csóka, Jean-Marc Guehl, Michael Köhl, Ivo Kupka), w wyniku głosowania
mandaty członków Rady na obecną kadencję uzyskali: Jean-Marc Guehl (INRA,
Francja) i Michael Köhl (Uniwersytet w Hamburgu, Niemcy).
Ustalono, że tegoroczna Plenarna Konferencja EFI odbędzie się w Uppsali
(Szwecja).
REPORT ON THE ANNUAL CONFERENCE OF THE EUROPEAN
FOREST INSTITUTE
Summary
The Annual Conference of the European Forest Institute (EFI) was organised on 15th
October 2010 in Dresden. The Conference was accompanied by a seminar on biomass
from forests and other lands.
Keywords: EFI, programme, report, research
DZIAŁALNOŚĆ NAUKOWA PROFESORA RYSZARDA
BABICKIEGO
Profesor dr hab. Ryszard Babicki, członek rzeczywisty PAN,
wieloletni Dyrektor Instytutu Technologii Drewna w Poznaniu.
Wybitny specjalista z zakresu chemicznej technologii drewna. Szerokie i wielopłaszczyznowe zainteresowania dotyczące m.in. takich zagadnień, jak: hydroliza i termoliza drewna,
zastosowanie środków chwastobójczych do zwiększania przeżywiczenia drewna, badania nad składem różnych gatunków
drewna i inne.
W dniu 16 grudnia 2010 roku zmarł prof. dr hab. Ryszard Babicki, jeden ze współtwórców Instytutu Technologii Drewna w Poznaniu. W Instytucie przepracował
57 lat, będąc jego dyrektorem naczelnym 21 lat, od roku 1970, awansując od stanowiska asystenta i jednocześnie zdobywając kolejne stopnie i tytuły naukowe.
W 1994 roku został członkiem rzeczywistym PAN, będąc od roku 1978 profesorem zwyczajnym. W roku 2004 w uznaniu za zasługi dla rozwoju nauki i osiągnięcia badawcze uchwałą Senatu Akademii Rolniczej w Poznaniu został wyróżniony tytułem doktora honoris causa tej uczelni.
Podstawowym obszarem działalności naukowej profesora dr. hab. R. Babickiego była chemiczna technologia drewna. Jego bogaty dorobek w tym zakresie
obejmuje zarówno prace o charakterze poznawczym, jak i stosowane licząc ponad
200 pozycji w tym około 70 oryginalnych rozpraw naukowych, 100 artykułów
i referatów naukowych, 3 monografie. Wyniki swoich badań Profesor publikował
w czasopismach krajowych i zagranicznych.
Na szczególne wyróżnienie zasługuje działalność Profesora dotycząca innowacyjności w przemysłach opartych na drewnie. Jest On autorem lub współautorem wielu patentów, opracowań technologicznych wdrożonych w przemyśle oraz
nieopublikowanych sprawozdań z prac naukowo-badawczych1.
Zainteresowania naukowe Profesora Babickiego były wielopłaszczyznowe
i koncentrowały się zarówno na problemach takich jak: hydroliza i termoliza
1
Wykaz ważniejszych publikacji prof. R. Babickiego znajduje się w opracowaniu:
Technologia drewna wczoraj, dziś, jutro. Studia i szkice na Jubileusz Profesora Ryszarda Babickiego. Poznań, ITD, 2007
140
drewna, przerób żywicy balsamicznej i ekstrakcyjnej oraz oleju talowego, uszlachetnianie produktów, jak również badaniach właściwości chemicznych drewna. Jednocześnie też należy zwrócić uwagę na wieloletnie, kompleksowe prace poświęcone termolizie drewna, które obejmowały badania nad zwęglaniem
różnych gatunków drewna oraz jego drobnych odpadów, w tym trocin, a także
nad regeneracją węgla aktywnego. Do szczególnych dokonań należy zaliczyć
opracowanie nowej przemysłowej technologii zwęglania drobnowymiarowych
odpadów drzewnych w piecu wielopółkowym typu Herreshoffa. Istotnymi walorami poznawczymi tych badań było wyjaśnienie szeregu zjawisk związanych
z procesem zwęglania drobnych odpadów lignocelulozowych, a także ich aktywacji. Równie wartościowe są wyniki badań nad hydrolizą drewna odpadowego,
a zwłaszcza trocin, w celu otrzymania drożdży paszowych. Trafne zastosowanie
w nich tzw. ryskiej metody hydrolizy pozwoliło na uzyskanie znacznej efektywności procesu.
Wyniki prac poświęconych przerobowi żywicy i oleju talowego oraz uszlachetnianiu pozyskanych produktów, realizowanych pod kierunkiem prof. R. Babickiego, umożliwiły zarówno zwiększenie wydajności procesu, jak i polepszenie
jakości produktów.
Na wyróżnienie zasługują nowatorskie badania nad zastosowaniem środków chwastobójczych do zwiększenia przeżywiczenia drewna. Te prekursorskie
w Polsce prace miały charakter kompleksowy i interdyscyplinarny. Uczestniczyli
bowiem w nich, oprócz pracowników naukowych Instytutu Technologii Drewna, leśnicy, entomolodzy, technolodzy produkcji i ekonomiści. Obszerne badania natury podstawowej i utylitarnej doprowadziły do opracowania technologii
oraz budowy urządzeń, a także założeń ekonomicznych otrzymywania i przerobu
sztucznie przeżywiczonego drewna sosnowego.
Znaczące miejsce w dorobku naukowym prof. R. Babickiego zajmowały
badania nad składem chemicznym różnych gatunków drewna w zależności od
wieku i zasięgu naturalnego, wzbogacające stan wiedzy z tego zakresu o szereg
istotnych aspektów. Podobny charakter miały prace nad zmianami właściwości
chemicznych i fizykochemicznych drewna buka pod wpływem obróbki hydrotermicznej. Jego wyniki zyskały zainteresowanie i uznanie w wielu ośrodkach
naukowych na świecie.
Profesor R. Babicki, kierując Instytutem przez ponad 20 lat, inicjował wiele
badań niezbędnych dla rozwoju przemysłu drzewnego. Jednocześnie godził obowiązki wynikające z pełnionej funkcji z powinnościami pracownika naukowego, czego przejawem było również łączenie działalności naukowej z aktywnym
udziałem w życiu publicznym i sprawowanie zaszczytnych i odpowiedzialnych
funkcji. I tak, w latach 1975-1980 powierzono Mu kierownictwo problemu węzłowego 09-11 „Kompleksowe wykorzystanie surowca drzewnego w przerobie
przemysłowym”, a w latach 1986-1990 nadzorowanie Centralnego Programu Badawczego 6.5. „Materiałooszczędny przerób drewna”.
Działalność naukowa profesora Ryszarda Babickiego
141
Wyrazem uznania autorytetu naukowego prof. R. Babickiego było Jego wieloletnie członkostwo w licznych komitetach i radach naukowych, m.in. : ponad
20 lat przewodniczył Komitetowi Technologii Drewna Polskiej Akademii Nauk.
W uznaniu zasług, w 1996 roku został powołany na honorowego przewodniczącego Komitetu. Przez 17 lat był członkiem Centralnej Komisji Kwalifikacyjnej
ds. Kadr Naukowych, uczestniczył w pracach Komisji Problemowych Komitetu
Badań Naukowych, Rad Naukowo-Technicznych Ministerstwa Leśnictwa i Przemysłu Drzewnego oraz Ministerstwa Rolnictwa, Leśnictwa i Gospodarki Żywnościowej, rad naukowych instytutów, rad programowych i komitetów redakcyjnych
czasopism naukowych, takich jak: Sylwan, Folia Forestalia Polonica, Drewno.
Prace Naukowe. Doniesienia. Komunikaty.
W świetle przedstawionego materiału można powiedzieć, że Profesor R. Babicki swoim życiem i pracą dobrze zasłużył się Instytutowi Technologii Drewna
i całemu sektorowi drzewnemu w Polsce.
Za Radę Programową

pobierz - Drewno

Transkrypt

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