RESUMOA madeira de acácia-negra tem sido utilizada em nichos que conferem pouco valor agregado à esse material. Diante disso, este trabalho teve como objetivo analisar as deformações residuais longitudinais (DRL) e suas relações com propriedades da madeira de Acacia mearnsii. Para tanto, foram selecionadas 60 árvores em plantios com idades distintas (4 e 7 anos) no Município de Piratini, RS. As características de crescimento avaliadas consistiram em diâmetro à altura do peito (1,3 m; DAP), espessura de casca (EP) e altura comercial (h). As propriedades físicas avaliadas massa específica básica (ρ) e teorde umidade à base seca (Tu). Já o tempo de propagação de onda ultrassonora foi determinado em conformidade com o procedimento NBR 15521. As propriedades mecânicas foram o módulo de elasticidade dinâmico (Ed), bem como as propriedades descritas no procedimento normativo D143-94, através dos ensaios de flexão estática, compressão paralela às fibras e Dureza Janka. ADRLesuas relações com as propriedades da madeira mostraram-se semelhantes aos resultados encontrados na literatura para a madeira de espécies do gênero Eucalyptus. No entanto, em magnitude, tais níveis se mostraram sensivelmente menores, conferindo à madeira de acácia-negra no que se refere a esse parâmetro de qualidade, indicação para a confecção de produtos sólidos.

ABSTRACTThe black wattle wood has been used in niches that confer low value to this material. Therefore, this study aimed to analyze the longitudinal residual strain (LRS) and its relations with Acacia mearnsii de wild wood properties. To achieve this, 60 trees with 4 and 7 years were selected from a forest population located in Piratini, RS. Diameter at breast height (1.3 m; DBH), bark thickness (BT) and commercial height (h) were evaluated. The physical properties evaluated were specific gravity (ρ) and moisture content on dry basis (Tu). The propagation time of ultrasonic wave was determined as described in NBR 15521 and then the dynamic modulus of elasticity (Ed) was measured. The mechanical properties was evaluated according to D143-94 standard by static bending, parallel compression to fibers and Janka hardness tests. The LRS and its relations with the wood properties were similar to the results found in the literature for wood fromEucalyptus species. However, in magnitude, these levels were sensibly lower, givingblack wattleindication to produce solid wood products, when it comes to this quality parameter.

Foram avaliadas as propriedades físico-mecânicas de painéis aglomerados produzidos com diferentes proporções de madeira (Eucalyptus grandis) e bambu (Bambusa vulgaris). Os painéis foram produzidos utilizando o adesivo ureia-formaldeído com a adição de 0, 25, 50, 75 e 100% de bambu. Para cada tratamento, determinaram-se as propriedades físicas (massa específica; teor de umidade; absorção de água e inchamento em espessura após 2 e 24 horas de imersão em água) e mecânicas (flexão estática; ligação interna; e arrancamento de parafusos). Os resultados obtidos indicaram que o acréscimo das partículas de bambu proporcionou uma redução significativa na qualidade dos painéis para os parâmetros avaliados, apresentando uma maior absorção de água e uma menor resistência à flexão estática e ao arrancamento de parafuso.

It was evaluated the physical and mechanical properties of particleboard produced with different proportions of wood (Eucalyptus grandis) and bamboo (Bambusa vulgaris). The boards were produced using urea-formaldehyde adhesive with the addition of 0, 25, 50, 75 and 100% of bamboo. For each treatment were determined physical properties (specific gravity, moisture content, water absorption and thickness swelling after 2 and 24 hours water immersion) and mechanical properties (static bending, internal bond and screw withdrawal). The results indicated that the addition of particles of bamboo provided a significant reduction in the quality of panels for most parameters, showing higher water absorption and a lower resistance to static bending and screw withdrawal.

This study aimed to characterise the effect of thermal treatment on physical and mechanical properties of açoita-cavalo (Luehea divaricata) wood. To achieve this, samples were treated at 160, 180 and 200°C for 2 h in an oven (dry conditions). Physical and mechanical characterisation was performed by weight loss, dry specific gravity at 12%, equilibrium moisture content, volumetric swelling and shrinkage, water absorption, water repellence, static bending and brittleness tests. Roughness and colour tests were performed in order to evaluate the modified surface. Main findings showed that dimensional stability of thermally modified wood increased, while mechanical strength of wood decreased as a function of temperature. A darkening of wood and a decrease in roughness were observed.

O presente estudo objetivou analisar propriedades físicas da madeira termorretificada de quatro eucaliptos. Dessa maneira, foram selecionadas 20 árvores com aproximadamente 60 anos de idade de Eucalyptus botryoides, Corymbia citriodora, Eucalyptus paniculata e Eucalyptus tereticornis. Foram confeccionadas amostras próximas das regiões da medula e da casca, de modo a caracterizar a seleção dos lenhos juvenil e adulto, respectivamente. As amostras foram climatizadas ao teor de umidade de equilíbrio de 12%, condição inicial para tratamentos de termorretificação conduzidos a 200 °C, durante uma hora. As modificações oriundas da termorretificação proporcionaram um aumento da estabilidade dimensional das madeiras. Dentre as madeiras estudadas, a menos higroscópica foi a madeira adulta de Eucalyptus paniculata, sendo o maior e o menor incremento de estabilidade dimensional conferidos às madeiras de Eucalyptus tereticornis e Corymbia citriodora, respectivamente.

In this study, we aimed to analyze the physical properties of four thermally treated eucalyptuses. To this end, 20 trees (~60 years old) of Eucalyptus botryoides, Corymbia citriodora, Eucalyptus paniculata, and Eucalyptus tereticornis were randomly selected in the municipality of Charqueadas, Rio Grande do Sul state, Brazil. We prepared samples near the pith and bark of trees in order to characterize the selection of juvenile and mature wood, respectively. The samples were kept in a climatic chamber to obtain the equilibrium moisture content (~12%), which was the initial condition for the thermal treatments at 200 °C for 1 hour. Changes due to thermal treatment resulted in an increase in the dimensional stability of wood. Among the eucalyptuses, the lowest hygroscopicity was found for the mature wood of Eucalyptus paniculata, while the highest and the lowest increases of dimensional stability were observed for Eucalyptus tereticornis and Corymbia citriodora wood, respectively.

The color modifications in Eucalyptus grandis thermally modified wood were investigated. One hundred eighty specimens (10 x 10 x 200 mm) were prepared and thermally modified in an electric kiln for 4 and 8 h at 180-240ºC. The color parameters (L*, a*, b*, C*, h* and ΔE) were determined by the CIE-L*a*b* method on radial and tangential sections of untreated and treated wood. The results indicated the darkening of specimens in the radial and tangential sections. Both sections showed variation of L* between 73 and 30, a* between 9 and 5 and b* between 20 and 8. The thermally modified wood at 180 and 200ºC showed similar patterns, equally at 220 and 240ºC. The time of exposure indicated significance just in treatment at 200ºC.

Neste estudo, objetivou-se caracterizar a qualidade da madeira serrada de Pinus elliottii procedente de florestas resinadas e processadas em uma serraria instalada no município de São José do Norte (RS). Para tanto, selecionaram-se, do processamento de desdobro, quatro toras basais e quatro toras superiores para cada uma das três classes diamétricas existentes. As peças originadas foram analisadas pós-desdobro e pós-secagem em estufa convencional convectiva. Constatou-se, em razão da inexistência de tratos silviculturais na floresta, a incidência de nós, principalmente nas peças de toras superiores, influenciando a classificação qualitativa dessas peças de madeira. Em relação à operação de resinagem, esta contribuiu para a maior incidência de bolsas de resina nas peças de toras basais, além de que, influenciou na classificação qualitativa da madeira. O surgimento de defeitos após a operação de secagem não alterou a classificação da madeira tanto oriunda de toras basais como de toras superiores.

This study aimed to characterize the quality of Pinus elliottii sawn timber extracted from tapped forests and processed in a sawmill in São José do Norte (RS). Four butt logs and four upper logs for each of the three existing diameter grades were selected and sawed. The wood pieces were analyzed after sawing and after kiln drying. The presence of knots, which occurred due to the absence of forest management and influenced the qualitative classification of the wood pieces, was observed mainly in the samples from upper logs. The process of resin tapping contributed to a higher incidence of resin pockets in the samples from butt logs, also influencing the qualitative classification of the samples. The appearance of drying defects did not modify the classification of the wood samples from butt and upper logs.

The present study describes the effect of thermal rectification on physical and mechanical properties of Eucalyptus grandis wood at different levels of temperature and time. Samples of Eucalyptus grandis wood (10 × 10 × 200 mm) were heat-treated at 180, 200, 220 and 240 °C during 4 and 8 hours. The mechanical properties of heat-treated and untreated samples were determined by static bending tests. The physical properties were determined by weight loss and swelling tests. The results showed that modulus of elasticity, modulus of rupture, weight loss, volumetric swelling and linear swelling were affected significantly by the thermal rectification. However, the length of exposure influenced just weight loss, while the temperature influenced all the studied properties of heat-treated wood. More significant modifications with treatments at a temperature of 200 °C or higher were found in the properties of heat-treated wood.