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Particles of flooded gum (Eucalyptus grandis) were bonded using three bio-based adhesives - anhydrous citric acid (CA), tannin-citric acid (TCA) and ricinoleic acid (RA) - from renewable sources and hot pressed to produce medium density particleboard (MDP). The bonding capacity of such adhesives and properties of the MDP were evaluated and compared to the requirements of seven grades of particleboards, according to the EN 312 (2010) standard. The RA did not create adhesion reaction with the wood particles. Adhesives formulated with CA and TCA presented capacity to bond eucalyptus particles into MDP confirmed by esterification reactions of the FTIRS analysis. MDP bonded with CA met requirements as high as grade P5 of the EN 312 (2010) standard for static modulus of elasticity (MOE) and internal bond (IB) and P2 for modulus of rupture (MOR). Panels bonded with TCA met requirements up to grade P3 for MOE, however, did not withstand water absorption., Za izradu iverice srednje gustoće (MDP) upotrijebljeno je iverje drva eukalipta (Eucalyptus grandis) lijepljeno trima ekološki prihvatljivim ljepilima dobivenim iz obnovljivih izvora na bazi anhidrida limunske kiseline (CA), taninsko-limunske kiseline (TCA) i ricinoleinske kiseline (RA) te prešano u vrućoj preši. Kvaliteta lijepljenja tim ljepilima i svojstva iverice ocijenjeni su usporedbom sa sedam klasa uporabe prema normi EN 312 (2010). Ljepilo RA nije uspjelo povezati drvno iverje. Ljepila CA i TCA pokazala su sposobnost lijepljenja eukaliptova iverja pri izradi MDP ploče, što je potvrđeno reakcijom esterifikacije u FTIR analizi. MDP ploča izrađena primjenom CA ljepila udovoljava visokim zahtjevima klase uporabe P5 prema EN 312 (2010) za modul elastičnosti (MOE) i čvrstoću na raslojavanje (IB) te klase P2 za modul loma (MOR). Ploče izrađene uporabom TCA ljepila ispunile su zahtjeve klase uporabe P3 za modul elastičnosti (MOE), ali nisu zadovoljile zahtjeve o upijanju vode.

Modulus of elasticity (MOE) of Douglas-fir ( Pseudotsuga menziesii) lumber loaded in parallel to grain tension was evaluated by nondestructive techniques (transverse vibration and longitudinal stress wave) and the results were correlated to the actual properties. Nondestructive parameters of specific gravity, wave frequency and attenuation and wave speed were measured. Destructive tests were performed with the use of static tension and bending techniques. Regression analyses were performed to correlate all nondestructive and destructive techniques. Results showed the MOE in static bending can be predicted with good efficiency. The correlation coefficients (R) for this test ranged from 0.818 to 0.941. The maximum tensile strength presented a poor correlation to the nondestructive parameters with the highest R=0.582.

http://dx.doi.org/10.5902/1980509819609Os objetivos deste estudo foram: avaliar a durabilidade natural de três espécies de tauari (Couratari guianensis Aublet, Couratari oblongifolia Ducke & Knuth R. e Couratari stellata A.C.Smith), relatar os parâmetros colorimétricos de acordo com o sistema CIE L * a * b * 1976 assim como mostrar a aparência dos blocos de madeira antes e após o ataque. Dois fungos de podridão-parda [Gloeophyllum trabeum (Persoon ex Fries) Murril. e Lentinus lepideus Fr.] e dois de podridão-branca [Trametes versicolor (Linnaeus ex Fries) Pilat e Ganoderma applanatum (Pers. ex Wallr.)] foram utilizados. A madeira de tauari foi classificada como "moderadamente resistente" a "resistente" quando exposta aos fungos Gloeophyllum trabeum, Trametes versicolor e Ganoderma applanatum. O conteúdo de extrativos das amostras atacadas diminuiu quando comparado com o controle, exceto Couratari stellata expostos a Ganoderma applanatum. Por outro lado, os conteúdos de cinzas aumentaram quando comparados com o controle, exceto para a madeira de Couratari stellata exposto ao Gloeophyllum trabeum. Todos os blocos de madeira atacados e as serragens tornaram-se mais escuras, exceto para a serragem de Couratari stellata exposto ao fungo Trametes versicolor, e mais vermelho do que a amostra sem ataque. O ΔE * médio do bloco de madeira e serragem, atacados, atingiram 29,5 e 14,3, respectivamente.

Recycled pulp of old corrugated containers (OCCs) was studied as a possible fiber source for wood-fiber cement (WFC) sheets. This industry currently largely relies on kraft pulp, an expensive fiber source. Thus, WFC sheets were made using less costly OCC fibers utilizing various types of treatments including fiber fractionation (FF) and refining to 500 and 400 Canadian Standard Freeness (CSF) to determine the effect of these treatments on the sheets strength. Unprocessed virgin kraft fiber of radiata pine (Pinus radiata) was used as control for comparison purposes. The unprocessed OCC pulp furnish yielded an initial freeness of 635 CSF; after fractionating, however, it was increased to 754 CSF. OCC pulp presented a kappa number of 47, compared to 23.7 for P. radiata. Fractionating OCC pulp was effective in raising the range of long fibers in the stock from 68 percent to 85 percent, before and after fractionating, respectively. Results from WFC sheets made in laboratory showed that there was no significant difference in board strength among boards made with unprocessed OCC fibers, fractionated and refined OCC, and P. radiata fibers. However, sheet strength decreased when refined OCC fibers were used. The results suggest that OCC fibers can produce WFC sheets with desirable characteristics compared to those of unrefined virgin kraft fiber of P. radiata.

Panels were produced with strips of bamboo (Guadua magna) in layers crossed at angles of 90° and bonded with phenol-formaldehyde or PVA based resin, glued in three and five plies. The panels were tested and the physical and mechanical properties determined. The tests were primarily related to the commercial adhesives used as well as the number of layers of bamboo used. The density ranged from 0.690 to 0.768 g.cm-3. Panels bonded with PVA resin showed low mechanical strength, with MOR between 6.7 and 7.8 MPa. Those bonded with phenol-formaldehyde adhesive showed high strength, with modulus of rupture (MOR) ranging from 55.5 to 87.0 MPa, which is excellent for boards similar to wood-based panels. Panels with phenolic resin also had reduced thickness swelling, up to 8.4%. The panels made with three layers showed higher resistance to bending than those made with five layers. © 2015, Federal University of Lavras. All rights reserved.

This experiment evaluated the utilization of the recently identified Brazilian giant bamboo, Guadua magna (Londoño & Filg.) to manufacture medium density particleboard. Four board types were tested: two of them exclusively with particles of bamboo and two in a mixture of bamboo with Pinus taeda wood particles. The target density of the panels was 0.65 g/cm³ for all treatments. The particleboards were bonded using 8% content of urea-formaldehyde (UF) and phenol-formaldehyde (PF) resins, based on dry weight mat. Mechanical, physical and nondestructive properties of the panels were assessed. The particleboards produced with PF showed better dimensional stability than UF particleboards. The addition of wood particles improved the mechanical properties of E M, fM and IB. The flexural properties of the panels (E M, fM) could be modeled using either E Md or density and the models fitted presented high predictability (>66%).

In the first part of this study, the feasibility of manufacturing resin-bonded particleboard from the recently identified Brazilian giant bamboo (Guadua magna) was evaluated. In this second part, the main goal was to study the material properties of the cement and gypsum-composites made from that bamboo species. The effect of CaCl2 addition in the physical and mechanical properties was also evaluated. Initially, the hydration test was performed to determine the inhibition index of the bamboo particles in the cement and gypsum setting. Three concentrations of CaCl2 were used to produce bamboo cementbonded particleboards (BCBP): 0%, 2% and 4%. CaCl2 was not added into bamboo gypsum-bonded particle boards (BGBP). Mechanical and physical properties were evaluated and nondestructive testing was performed as well. The inhibition index of Guadua magna in the cement or gypsum setting was classified as “low inhibition”. The addition of CaCl2 at bamboo-cement boards increased the internal bonding and reduced the water absorption. Other properties were not significantly affected. The bamboocement boards presented higher bending strength and lower moisture content than bamboo-gypsum boards.

This study aims to evaluate the resistance of three types of particleboard panel to biodeterioration, two of which bonded with synthetic resins and one bonded with PVC plastic. Composite panels were made using sugar cane straw particles as raw material which were bonded together with urea-formaldehyde (UF), tannin-formaldehyde (TANI) and PVC plastic (PVC) resins. Decay tests were performed following procedures outlined in the ASTM D2017-81/1994 standard, whereby sample specimens were subjected to attack by white rot fungus Trametes versicolor and brown rot fungus Gloeophyllum trabeum using pine (Pinus sp.) and embaúba (Cecropia sp.) as reference timber. Panels bonded with PVC resin were rated ‘resistant’ to attack by both fungi while those bonded with UF and TANI resins were rated ‘slightly resistant’ to their attack.

Laminated strand lumber and oriented strand lumber (LSL/OSL) are structural composite lumber, which has beenrecently introduced in the building construction market, as an alternative to solid wood utilization. This research aimed to analyze thetechnical feasibility of producing LSL and OSL. Additionally, it was also investigated the effect of using different lengths of particles onphysical and mechanical properties of the composites and comparing it to Chrysophyllum sp solid wood. Six wood panels wereproduced, utilizing particles of 15 and 30 centimeters of length, divided into two analyses (OSL/LSL), with three repetitions in eachone. The following tests were performed: static bending (MOE//, MOR//) non-destructive testing (MOEd//), parallel compressionstrength (COMP//); thickness swelling (TS), water absorption (AA) and linear expansion (EL) for 2 and 24 hours. These tests wereconducted according to the ASTM D 5456 (ASTM, 2006). It was not identified the effect of particle length on mechanical properties.On the other hand, the composite produced with shorter particles (OSL) presented better dimensional stability than the LSL, producedwith longer ones. Flexural properties and compression strength of OSL/LSL composites presented values close, but still lower, thanthose observed for solid wood.

The objective of this work was to examine quantitatively the color changes of six clones of Hevea brasiliensis (IAN 717, IAN 873, GT 711, AVROS 1301, RRIM 600, and Tjir 16) and two cypresses ( Cupressus sp. and Cupressus glauca ) upon fungal attack. Samples were exposed to the fungi Gloeophyllum striatum and Phanerochaete chrysosporium according to ASTM D 2017. Wood color was measured in the L ∗ a ∗ b system. Changes in the colorimetric parameters were calculated by the difference between attacked and control samples. None of the rubberwood clones showed weight loss below 25% and therefore could not be classified as resistant, but clones AVROS 1301, RRIM 600, and Tjir 16 were borderline. Both cypresses were resistant to P. chrysosporium , but only Cupressus sp. was resistant to G. striatum . The red tint of all samples exposed to both fungi was slightly intensified (Δ a ∗ > 0), except for RRIM 600. The yellowish tint was intensified as well, except for RRIM 600 and Tjir 16 exposed to G. striatum . Samples attacked by G. striatum were darker than controls (Δ L ∗ P. chrysosporium were lighter (Δ L ∗ > 0). Color variation mean values (Δ E ∗ ) ranged from 3.98 to 12.33, attaining the levels appreciable to very appreciable color difference. Extraction of the attacked samples with ethanol–toluene plus hot water removed red and yellow chromophore pigments, causing color variations perceptible to the naked eye.

This paper aims to evaluate whether a thermal post-treatment can be applied to enhance the performance of oriented strandboard (OSB). Samples from 42 commercial OSBs were heat-treated at two temperature levels (190 and 220 °C) and for three heating times (12, 16, and 20 min) using a single opening hot-press. For comparison, control boards were kept untreated. These samples were exposed for eight months to outdoor weathering, and then their physical and mechanical properties were evaluated, as was their decay resistance against the brown-rot (Gloeophyllum trabeum [Persoon ex Fries] Murrill) and white-rot (Trametes versicolor [Linnaeus ex Fries] Pilat Murrill) fungi. The results indicated that the heat-treated samples maintained their mechanical properties at a much higher level after weathering than did the untreated ones. It was determined that the higher the treatment temperature, the better the residual mechanical properties. The proposed thermal treatment also slightly improved the decay resistance against the two evaluated fungi, but it was not enough to change the resistance class of the OSB.

RESUMO O objetivo deste trabalho foi avaliar o efeito da adição de microssílica em três porcentagens (0, 20 e 30%) sobre as propriedades físicas e mecânicas de painéis cimento-madeira de Eucalyptus urophylla compostos por três relações madeira:casca (100:0, 95:5 e 90:10). Os resultados mostraram que o efeito mais significativo do aditivo sobre os painéis produzidos ocorreu naqueles que continham casca, e que a adição de 20% do aditivo foi mais eficiente sobre as propriedades físicas e mecânicas. ABSTRACT This work’s objective was to evaluate the effect of three percentages of addition of microsilica (0, 20 and 30%) on the physical and mechanical properties of wood-cement bonded particleboards of Eucalyptus urophylla composed by three wood:bark ratios (100:0, 95:5 and 90:10). Results showed that the most significant effect of the additive on the produced panels was in those containing bark, and that of 20% of additive was more efficient on the physical and mechanical properties.

Control and hot water treated particles of cypress ( Cupressus spp.) were used to manufacture cement-bonded particleboards (CBPB). Three replications were carried out for each treatment, totaling six single layered boards. Physical and mechanical properties of the boards were evaluated according to ASTM D 1037-96a [Annual Book of ASTM Standards, vols. 04–09. Philadelphia: American Society for Testing and Materials––ASTM, ASTM D 1037-96a, 1998] standard. The wood of cypress showed suitability as raw material for the manufacture of CBPB. All the properties of cypress CBPB were higher than the Bison HZ type building boards used as reference. The light color and easy wood processing of cypress wood are favorable parameters for panels manufacturing. The results corroborate those reported for CBPB using pine, rubberwood, acacia, babassu, and eucalyptus particles. The CBPB were also submitted to fungi decay resistance test according to ASTM D 2017-81 [Annual Book of ASTM Standards, vols. 04–09. Philadelphia: American Society for Testing and Materials––ASTM, 1994-e1. ASTM D 2017-81, p. 324–8] standard and exposed to the attack of Gloeophyllum trabeum (Persoon ex Fries) Murr. and Trametes versicolor (Linnaeus ex Fries) Pilat. Twelve specimens were tested for each treatment and the average weight loss was determined after 12 weeks of exposure. Laboratory tests showed that there was no measurable wood degradation (weight loss). Fungi mycelium did not even cover completely the surface of the specimens. CBPB when exposed to both brown- and white-rot fungi, rather than weight loss, showed weight gains ranging from 2% to 4%. Therefore, CBPB is technically suitable for exterior use where both moisture and favorable conditions for fungi development are present.

Six eucalypts species Eucalyptus camaldulensis Dehnh., E. citriodora Hook, E. cloeziana F. Muell, E. grandis Hill ex. Maiden, E. pilularis Sm., and E. urophylla S. T. Blake) and two clones of rubberwood ( Hevea brasiliensis (Willd ex Adr. de Juss) Muell. Arg.), planted in Brazil, were used to manufacture wood cement-bonded particleboard (CBWP). Boards measuring 450 × 450 × 13 mm were manufactured in a wood/cement/water ratio of 1:4:1, by weight; nominal density of 1.4 g/cm 3 and 4% of additive (CaCl 2 ·H 2 O) using a mixture of each eucalypts species (50%) and the two clones of rubberwood (25% of each). Three replications were fabricated for each treatment and the physical and mechanical properties of the boards evaluated according to ASTM D 1037-96a [Standard test methods for evaluating properties of wood-base fiber and particle panel materials. ASTM D 1037-96a, vol. 04.09. ASTM, 1998]. The results of modulus of elasticity ranged from 4090 to 4771 MPa. The results of modulus of rupture ranged from 5.8 to 6.4 MPa. Internal bond were similar to those found in the literature. Screw withdrawal values were up to 2020 N. The panels showed very good dimensional stability. The mixture of species and also the addition of calcium chloride have improved the physical and mechanical properties of the panels. Decay fungi tests were conducted according to the ASTM D 2017-81 [Standard test method for accelerated laboratory test of natural decay resistance of woods. ASTM D 2017-81, vol. 04.09. ASTM, 1994-e1. p. 324] for two representative wood-attacking fungi, a brown-rot fungus Gloeophyllum trabeum (Persoon ex Fries) Murrill and a white-rot fungus Trametes versicolor (Linnaeus ex Fries) Pilat. Twelve samples were tested and after 12 weeks of exposure the average weight loss was determined. The test indicated that CBWP was classified as “highly resistant” and the samples gained weight.

Chapas de partículas de cimento-madeira foram confeccionadas com a madeira de quatro clones de Hevea brasiliensis Müll. Arg. (seringueira): IAN 717, IAN 873, GT 711 e AVROS 1301. Confeccionaram-se as chapas na proporção de 1:4:1 (madeira:cimento:água) por peso e nas dimensões de 450 x 450 x 13 mm e densidade nominal de 1,4 g/cm³, com a adição de 4% de cloreto de cálcio di-hidratado (CaCl2.2H2O) como acelerador. Foram testadas partículas fervidas e não-fervidas dos quatro clones, totalizando oito tratamentos, sendo em cada um destes, com quatro repetições, avaliadas as propriedades mecânicas e físicas das chapas, segundo a norma ASTM D 1037 - 96a. De forma geral, os melhores resultados de propriedades físicas e mecânicas foram obtidos nas chapas com partículas do clone AVROS 1301. No teste de hidratação do cimento, a madeira de seringueira in natura foi classificada como de "inibição extrema", porém com a adição de CaCl2 o foi como de "baixa inibição". Essa madeira se mostrou tecnicamente viável à produção de chapas de cimento-madeira, independentemente do clone.

This research is part of a general study on the properties of oriented strandboard (OSB) using wood strands of species from Brazilian planted forests. The OSB industry is the latest wood related activity established in Brazil. In this particular part of the study, 80 mm long strands of Pinus taeda L. were bonded using two resin types (urea-formaldehyde and phenol-formaldehyde) at two levels of resin content (5% and 8%) to produce three-layer cross-aligned OSB to a face to core layer ratio of 1:2 and target density of 0.75 g/cm3. Physical and mechanical properties of the boards were evaluated according to ASTM standard D 1037-96a (1997) and the results compared to standards available as requirements for commercial structural panels. The results indicate that all the mechanical properties evaluated were above the requirements set forth by the Canadian standard CSA O437.0 (1993) for structural panels. The results of Janka hardness were in average 4 folds higher than the minimal requirements for Grade R-1 waferboard. Screw withdrawal values were also above the minimum required by grade M-3 of ANSI A208.1 standard (1993). Nevertheless, values of thickness swelling and water absorption were very high. The low dimensional stability may be related to the high density of the boards (“springback” effect) and also to the fact that no wax was used.

In this study, the biological resistance and physical–mechanical properties of laboratory made particleboard and flakeboard using natural and acetylated particles and flakes of cypress (Cupressus spp.), planted in Brazil, were examined. Boards with 10% urea–formaldehyde resin were pressed for 8 min at 160°C. The experimental design was a 22 complete factorial, with four replicates per treatment, totalling 16 single-layer panels of 550×500×13 mm with a mean density of 0.70 g cm −3 . The panels were cut into samples, and their physical and mechanical properties determined according to ASTM D 1037-96a standard. Cypress panels were tested in the laboratory for durability, according to ASTM D 2017-81. Control panels were classified as “resistant” when exposed to the brown-rot fungus, Gloeophyllum trabeum, while the acetylation process improved the resistance of the cypress panels, which were subsequently classified as “highly resistant”. The same effect was observed for specimens exposed to the white-rot fungus Trametes versicolor. Regarding mechanical properties, the manufactured cypress panels should be classified as grade M-3, according to ANSI A208.1, except for internal bond and modulus of elasticity of flakeboards and particleboards, respectively. Dimensional stability of flakeboards and particleboards was very low. Acetylated panels showed better physical but lower mechanical properties than the control panels. Swelling of acetylated cypress flakeboards, after 2 and 24 h of water immersion, was lower than the maximum required by EN 312-4 standards. Cupressus spp. wood was shown to be very suitable to be processed into reconstituted panels.

This experiment evaluated the use of the material of the outer coconut shell of babaçu (Orbignya sp.), a palm tree from Brazil, for the manufacture of particleboards bonded with Portland cement. Four treatments were analyzed at two target densities (1.2 g/cm3 and 1.4 g/cm3) and two levels (0% and 4%) of addition of calcium chloride. The lignocellulosic material from babaçu presented a low cement inhibition index according to the hydration test. Testing of manufactured panels showed that good physical and mechanical properties were achieved at the treatment levels tested.

This study evaluates whether the mechanical properties of modulus of rupture (MOR) and modulus of elasticity (MOE) of wood-fiber cement (WFC) sheets are correlated with the nondestructive parameters of stress wave velocity and density of the material. Longitudinal stress wave technique was used to evaluate WFC nondestructively using a total of 117 specimens (measuring each 241 x 51 mm) obtained from 39 WFC sheets. The aim was to establish the correlation between dynamic versus static MOE of the material for predicting the actual mechanical property. Even though short dimension specimens were used, results obtained were encouraging. A correlation coefficient (R) of 0.828 was found when the static MOE of the material was used as a function of nondestructive parameters. A multivariate linear regression analysis using the specimen's density, wave velocity, and dynamic MOE provided the strongest correlation to the static MOE. The correlation observed for MOR as a function of static MOE is within the normal range obtained for wood composites. A nondestructive evaluation (NDE) using full size WFC sheets is recommended and can probably improve the relationship between the static and the predicted MOE.

RESUMO O objetivo do trabalho foi avaliar a resistência natural de chapas de partículas orientadas (OSB) confeccionadas com partículas de Hevea brasiliensis Müll.Arg. aderidas com as resinas sintéticas uréia- formaldeído (UF) e fenol-formaldeído (FF), a 5% e 8%, expostas a fungos xilófagos em condições de laboratório. No ensaio acelerado de laboratório as amostras foram submetidas ao ataque dos fungos de podridão-parda Gloeophyllum trabeum (Pers. : Fr.) Murril, Coniophora puteana (Schumach. : Fr.) P. Karst., Meruliporia incrassata (Berk. & M.A. Curtis) Murrill e também aos fungos de podridão-branca, Fomes annosus (Fr. : Fr.) Cooke, Trametes versicolor (L. : Fr.) Pilát, Ganoderma applanatum (Pers.) Pat., Bjerkandera fumosa (Pers. : Fr.) P. Karst. e Phanerochaete chrysosporium Burds. Dentre os fungos de podridão-parda, o Gloeophyllum trabeum causou a maior perda de massa nos corpos-de-prova testados. Dentre os fungos de podridão-branca, Trametes versicolor, Phanerochaete chrysosporium e Ganoderma applanatum causaram as maiores perdas de massa, sem diferença significativa para o Gloeophyllum trabeum. A resina FF proporcionou maior resistência à ação dos fungos nas chapas OSB, o mesmo fato ocorrendo com o maior teor de resina. O fungo Coniophora puteana foi altamente sensível ao tipo de resina aplicado, enquanto o Bjerkandera fumosa demonstrou reduzida ação nas concentrações mais altas de ambas as resinas. O fungo Fomes annosus apresentou degradação insignificante para todos os tratamentos de chapas OSB. ABSTRACT This work aimed to evaluate the natural durability of oriented strandboards (OSB) manufactured with strands of Hevea brasiliensis Müll.Arg. bonded with 5% and 8% of urea-formaldehyde (UF) and phenol-formadehyde (FF) resins, exposed to xilophagous fungi under laboratory conditions. In accelerated laboratory test decay, samples of OSB were exposed to the following fungi: the brown-rot fungi Gloeophyllum trabeum (Pers. ex Fries) Murr., Coniophora puteana (Schumach. : Fr.)P. Karst., Meruliporia incrassata (Berk. & M.A. Curtis) Murrill as well as the white-rot fungi Fomes annosus (Fr. : Fr.) Cooke, Trametes versicolor (L. : Fr.) Pilát, Ganoderma applanatum (Pers.) Pat., Bjerkandera fumosa (Pers. : Fr.) P. Karst. and Phanerochaete chrysosporium Burds. Among the brown-rot fungi, the Gloeophyllum trabeum was the most aggressive, showing the highest loss of mass. Trametes versicolor and Ganoderma applanatum confirmed the preference for broadleave species. All oriented strandboards at lower UF resin contents were more degraded by Phanerochaete chrysosporium, Trametes versicolor, Ganoderma applanatum, Merulia incrassata, Coniophora puteana and Gloeophyllum trabeum, with high rate of loss of mass. Coniophora puteana showed small loss of mass when FF resin was applied. Bjerkandera fumosa showed low loss of mass only at higher resin content. Oriented strandboards exposed to Coniophora puteana showed insignificant OSB degradation.

Oriented strandboard made of pine, cypress and rubberwood. This research evaluated the physical- mechanical properties of oriented strandboards (OSB) using strands of pine, cypress and a mixture of two clones, of rubberwood. The ratio of face to core layer was 1:2:1. Boards measuring 450 x 450 x 13 mm were bonded with 5% and 8% of urea-formaldehyde (UF) and phenol-formaldehyde (FF) resins, based on the dry weight of the particles, with density of 0.75 g/cm 3 . The boards were evaluated according to ASTM D 1037 and compared with CSA O437.0 and ANSI A.208.1 standards. In general, as the resin level increased, mechanical and physical properties also improved, and panels with 8% FF resin showed the best performance. Cypress OSB made with FF resin showed higher mechanical properties, except internal bond than required by aforementioned standards. OSB panels were also dimensionally unstable since water absorption and thickness swelling values were very high. The mechanical properties of rubberwood OSB were higher than required by CSA O437.0 and ANSI A.208.1, except for internal bond, since only panels bonded with 8% of FF resin met the requirements of the CSA O437.0 standard.

The objective of this paper was to propose a thermal post-treatment to improve the dimensional stability of oriented strandboard (OSB). Commercial OSB panels were obtained from an industrial batch and thermally treated in a single opening hot-press at two temperature levels (190 and 220 °C) and three duration times (12, 16 and 20 min). Dimensional stability, mechanical properties, chemical composition and surface color were studied. The results pointed-out that the proposed treatment can be applied to significantly improve the OSB dimensional stability by reducing thickness swelling, water absorption, and equilibrium moisture content in comparison to the untreated board. The mechanical properties were partially affected with reduction in modulus of rupture and without any adverse effect on the other properties. Chemical degradation occurred, mainly in relation to hemicelluloses contents, reducing equilibrium moisture content. The board surface became darker and this characteristic was correlated with the observed properties improvement. Dimensional stability properties were affected by both temperature and duration of the treatment, while the others mainly by temperature. The proposed thermal treatment can be recommended as a post-treatment to improve the OSB performance.

The objective of this research was to determine the physical and mechanical properties of oriented strandboard (OSB) using strands of Cupressus glauca Lam., before and after a thermal treatment, as well as to evaluate the susceptibility of the boards to fungi attack. Boards with nominal density of 0.70 g/cm 3 were produced with 5% and 8% of urea-formaldehyde (UF) resin. Physical and mechanical properties were evaluated according to ASTM D 1037 (1991) standard and compared with CSA O437.0 and ANSI A.208.1 standards. All mechanical properties were higher than those values required by both standards, except the modulus of elasticity in parallel axis. The thermal treatment slightly reduced the modulus of elasticity and stress at proportional limit, both in perpendicular axis, however improved significantly dimensional stability. Dimensional stability of the treated OSB was improved at the lower resin level but did not reach the maximum value required by the Canadian standard. Biological assay showed that heat-treated cypress OSB exposed to P. sanguineus reduced mass loss from 39% to 50%, while for G. trabeum the reduction was from 40% to 49%. Post thermal treatment of manufactured OSB (190oC, 720 s) can be the recommended method to reduce the hygroscopicity without great effect on mechanical properties and to protect panels against these fungi.