aPlywood can be used in the furniture industry and in civil construction due to its structural strength. However, for long useful life in construction, especially in tropical countries, it needs to undergo treatments against xylophagous organisms. The most common preservative treatment is the chemical chromated copper arsenate (CCA); there are alternatives, such as heat treatment, that do not use chemicals. The objective of this work was to evaluate the mechanical resistance of CCA and heat-treated plywood prepared at three different temperatures (160 °C, 180 °C, and 200 °C). Pinus taeda plywood with seven veneers and phenol-formaldehyde adhesive was produced and subjected to the preservative treatments. The results showed that the CCA treatment reduced the mechanical strength of the panels, while the heat treatment did not. Heat treatment also decreased panel hygroscopicity, indicating a better dimensional stability.

A utilização de resíduos é fundamental para a minoração dos impactos ambientais, consistindo as madeireiras nas principais fontes de geração de resíduos deste material, provenientes do procesamento da madeira. Painéis à base de madeira consistem em uma possibilidade de aplicação desses resíduos, e estudos recentes têm sido desenvolvidos visando a obtenção de melhor qualidade desses produtos. Esta pesquisa teve como objetivo produzir e avaliar painéis de partículas de média densidade (MDF) fabricados com resíduos de madeira de Pinus spp. com dimensões de partículas variadas e resina ureia-formaldeído como adesivo. As propriedades físicas e mecânicas investigadas, bem como os requisitos foram obtidos de acordo com a norma brasileira ABNT (2006). As propriedades físicas investigadas foram a densidade, teor de humidade e o inchamento em espessura e absorção de água após duas horas de imersão em água, e as propriedades mecânicas foram a resistência na tração perpendicular, módulo de elasticidade (MOE) e o módulo de ruptura (MOR). Três tratamentos foram delineados de acordo com o tipo de resíduo, no primeiro tratamento, os painéis foram produzidas com resíduos de folhas de madeira, no segundo tratamento foram utilizados resíduos provenientes do processamento da madeira, e o terceiro consistiu na composição de ambos. O primeiro tratamento apresentou ser o de menor variação nas propriedaes avaliadas (material mais homogêneo), e com relação as melhores propriedades físicas e mecânicas, estas foram provenienets do terceiro tratamento, que proporcionaram paineis de maior densidade, menor absorção de água e valores mais elevados para a resistência na tração perpendicular, MOE e MOR. Palavras-chave: painéis de média densidade, resídos de madeira, uréia formaldeído.

The use of wood-base panels in humid environments, in general, presents low durability due to contact with water. In order to increase durability and reduce the attack of fungi, studies had been developed using resin with zinc oxide (ZnO) nanoparticles. This work aimed to produce medium density fiberboard with urea-formaldehyde resin and melamine-formaldehyde adding 0.5% and 1.0% of ZnO nanoparticles for the physical properties evaluation. All treatments were classified as medium density according to ABNT NBR 15.316-2 (2015) with values ranging between 550 and 800 kg*m-³. No differences were found between the two commercial adhesives used. The addition of 1.0% of nanoparticles resulted in lower density panels, higher moisture contents, and, after immersion in water for 24 hours, higher values of swelling in thickness. These results are explained by the lower compaction of the boards due to rapid cure of the adhesive using higher percentages of ZnO nanoparticles. The best treatment of the panels was with melamine-formaldehyde resin and 0.5% of nanoparticles.

The Brazilian Code ABNT NBR 7190 (1997) is currently under review process and one of the proposals is the change and add of some test procedures. Several specimen geometric configurations and test conditions have been evaluated by the study committee CE-02:126.10. The aim of this paper was the analysis of the tensile strength perpendicular to the grain through the current Brazilian Code and from an adaptation of ISO 13910 (2005). Pine and Indian Cedar were used and simplified relationships were proposed. Numerical simulations were performed to identify the stress distributions in the specimens. The results obtained by ISO 13910 (2005) did not differ statistically for the two species. Brazilian standard method cedar had a higher strength value than pine. The simplified ratios obtained ranged between 0,017 and 0,123. The numerical simulations of ISO 13910 (2005) specimens showed predominant failure by tension in the lower fiber due to stress concentration.

Oriented strand board (OSB) panels, like plywood, are destined for structural use. Both of them may undergo preservative treatments that extend their lifetime and increase their resistance against weathering and xylophagous agents. One possibility is a heat treatment where the wood is exposed to temperatures above 130°C (403 K), which causes chemical, physical, and mechanical changes. The aim of this work was to produce OSB made of Pinus taeda thermally treated without replacement of atmosphere for an inert gas. The physical properties of density, moisture content, and thickness swelling in water immersion for 24 hour were evaluated. The mechanical properties of static bending were determined by the modulus of elasticity (MOE), modulus of rupture (MOR), and an internal bond test. Boards were heattreated at 160, 180, and 200°C (433, 453 and 473 K), and panels were produced with heat-treated strands at 160 and 180°C (433 and 453 K). The heat treatment of boards did not affect mechanical properties compared to the control treatment. The thermal treatment of strands reduced the physical and mechanical performances of the panels.

Cement-based composites with lignocellulosic residues (e.g. wheat straw, rice husk, and bagasse) as fillers have reduced density and cost. Pretreatments have been applied in these raw materials to improve their compatibility with cement. This work aimed to characterize composites made from cement and wheat straw particles that had been chemically treated (2% NaOH solution) at two different temperatures (30 °C and 60 °C). Values of bulk density (209 kg·m-3) and specific density (679 kg·m-3) were determined for wheat straw at 12% moisture content. Straw yield was 71.9% and the particle size distribution showed large concentrations of wheat straw particulate material between 5- to 10-mesh. Composites made with wheat straw particles, in comparison to the control treatment, showed half the density, i.e., from 1800 to 900 kg·m-3. Also, the stress x strain curve presented a higher deformation before failure. NaOH pretreatment did not affect the mechanical properties of wheat straw composites.

Oriented Strand Board is a structural wood composite with applications that require good physical and mechanical performance. The addition of ZnO nanoparticles is an alternative that has been studied in order to improve the properties of Oriented Strand Board panels. However, there is no information about its effect Oriented Strand Board. The aim of this work was to evaluate the influence of the addition of zinc oxide nanoparticles in two different percentages (0,25 % and 0,50 %) on the physical-mechanical properties of Oriented Strand Board panels produced with phenol-formaldehyde resin and on the heat transfer during hot-pressing. Oriented Strand Board panels were produced and tested according to European Standards. The addition of ZnO nanoparticles improved the dimensional stability of the panel, reducing its thickness swelling, and also increased the screw withdraw strength. The heat transfer during hot-pressing increased the temperature more quickly on boards with nanoparticles addition; on the other hand the final temperature of the control treatment was higher.

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