José Tarcísio da Silva Oliveira

Variação radial da retratibilidade e densidade básica da madeira de Eucalyptus saligna Sm.

RESUMO - A ultra-estrutura e a composicao quimica da madeira, bem como suas propriedades fisicas e mecânicas, variam significativamente entre especies, entre arvores de uma mesma especie e, mesmo, entre diferentes partes de uma mesma arvore. Com este trabalho objetivou-se o estudo dos parâmetros de retratibilidade e de densidade basica da madeira Eucalyptus saligna, com idade de 16 anos, proveniente de talhoes experimentais da EMBRAPA Florestas, de Colombo, Parana. As amostras foram retiradas a altura do DAP de quatro posicoes equidistantes a partir da medula em direcao a periferia, correspondendo a 0, 33, 66 e 100%, com dimensoes nominais de 1,0 x 2,0 x 3,0 cm, sendo a ultima dimensao no sentido longitudinal. Elas foram mantidas em câmara fechada com ventilacao, proximo de solucoes salinas supersaturadas, com o objetivo de proporcionar diferentes condicoes de umidade relativa. Uma vez atingidas as distintas condicoes de umidade de equilibrio, as amostras foram secas em estufa a 105 oC e obtidos os dados de retratibilidade e densidade basica da madeira nas posicoes mencionadas. Constataramse valores de contracao volumetrica mais baixos na regiao medular, apresentando um acrescimo para as demais posicoes. Comportamento semelhante foi observado para os coeficientes das contracoes lineares nas direcoes tangencial e radial. O fator anisotropico foi consideravelmente mais elevado na regiao medular, decrescendo substancialmente em direcao ao alburno. A densidade basica nao mostrou sinais efetivos de estabilidade, apesar de mostrar tendencia de aumento em direcao a periferia do tronco.

Variação do teor de umidade e da densidade básica na madeira de sete espécies de eucalipto

The occurrence of high moisture and density gradients inside of the tree is related with drying defects, especially those characterized by warp and split of the wood. The unequal behavior of wood pieces due to variation of these two properties can be attributed to differences within the wood that constitutes the log. Considering the importance of knowing the moisture and density gradients in eucalyptus trees, this work had as objective evaluating the variations of the moisture content and specific gravity in the radial and longitudinal directions of the trees of seven eucalypts species. Based on the results concerning the moisture distribution inside the tree, there was a great homogeneity in the species of E. paniculata and E. citriodora, sustained by the low values of variation coefficient and standard deviation. In these species, the moisture differential among the inner and outer parts of the log rarely reached 20%, while for the logs of E. urophylla and E. grandis, this diferencial reached 80%. In spite of the specific gravity general increased in the direction pith-to-bark, each species presented a specific profile of variation, also with variants for each height of the log.

Influência da idade e da posição ao longo do tronco na composição química da madeira de Eucalyptus grandis Hill ex. Maiden

The objective of this work was to study the chemical composition variation of the Eucalyptus grandis wood, of four different ages (10,14,20 and 25 years), from commercial stands. The samples were removed from three disks taken from the base and top of the first two 3 m logs, from sixteen trees (four per age), totalizing fourty-eight discs. The mean values of holocellulose, lignin and extractive contents were 69, 27 and 4%, respectively. The extractive and lignin contents increased with age, with greater concentrations near the base; the holocellulose content also decreased with age with greater concentrations in discs removed from the upper parts of the trunk.

Influência dos estrativos na resistências ao apodrecimento de seis espécies de madeira

In this work, the wood of six indigenous and two exotic species, previously extracted with different solvents, was exposed to the fungus Gloeophyllum trabeum, with the objective of determining which solvent was most efficient in removing the substances responsible for their resistance to decay. The samples were reduced to sawdust and extracted with cold and hot water, with a mixture of ethanol/toluene, dichloromethane, and methanol, and also totally extracted with hot water with ethanol-toluene and ethanol. After extraction, the samples were inoculated with the fungus, inside a plastic container. The results showed the remarkable resistance of Cedrela fissilis wood, even after total extraction, as evidenced by its low mass loss; the solvents were unable to remove the substance or substances that confer that durability. Non-extracted Amburana cearensis, Vanillosmopsis erythropappa, Machaerium scleroxylon and eucalypts (Corymbia citriodora and Eucalyptus gummifera) showed their typical resistance; when totally extracted, however, their mass loss was very high. As regarding individual solvents, in V. erythropappa and eucalypts, dichloromethane was the most efficient in removing the substance responsible for resistance. C. citriodora wood showed a low mass loss when it was extracted with cold and hot water, dichloromethane and natural (not extracted). Wood of A. cearensis extracted with the mixture ethanol/toluene had the most severe weight loss, while in M. scleroxylon the most efficient solvent was methanol.

Avaliação da retratibilidade da madeira de sete espécies de Eucalyptus

The variation of the retratibility in lumber is the main cause of the occurrence of drying defects, especially those characterized by warped and split wood. The different wood types present in the stem are related to the variation of these important physical properties. This work aimed to study the retratibily of seven eucalypt species. The retratibility parameters such as the variation in the pith to bark direction in the peripheral of the trunk were studied according the Brazilian Standard for the seven eucalypts. In general the results showed that the species of eucalypts studied have a high retratibility. Except for Eucalyptus tereticornis and E. pilularis the others species studied showed lower values of retratibility in the pith region.

Estudo de algumas propriedades mecânicas da madeira de um híbrido clonal de Eucalyptus urophylla X Eucalyptus grandis

The search for wood originated from reforestations destined to sawmill has been observed for many years, mainly for the Eucalyptus species. Searching for information to assist this market, the aim of this study was to determine some mechanical properties of the wood from a Eucalyptus urophylla x Eucalyptus grandis clonal hybrid, at two different ages and coming from coppice and reform. The results show that the wood of this clonal hybrid presents good technological characteristics and is the second best log (starting from 3,0 m), as to static bending properties (Module of Elasticity - MOE and Module of Rupture - MOR). The oldest trees (166 months - E2) which suffered two thinning presented the best results for the property of static bending and axial crushing (CA).

Influência da composição da resina tanino-uréia-formaldeído nas propriedades físicas e macânicas de chapas aglomeradas

In the production of the wood base particleboards, synthetic adhesives are used as melamina-formaldehyde (MF), phenol-formaldehyde (FF), urea-formaldehyde (UF), among others. Due to the high cost of these adhesives, researches that a seek the introduction of alterations in their formulations are important for the reduction of costs in the productive system. This work had as objective verify the influence of the several levels of Acacia mearnsii tannin in a commercial resin of urea-formaldehyde an the physical and mechanical properties of the particleboard. The particleboard was produced with Eucalyptus urophylla wood. They were four treatments: T1 - 100% of resin UF (control); (T2) 90% of the resin UF + 10% of the tannin 50%; (T3) 85% of the resin UF + 15% of the tannin 50% and (T4) 70% of the resin UF + 30% of the tannin 50%. The results showed that it is possible to add tannin to the resin urea-formaldehyde without to alter the physical and mechanical properties of the boards.

Influência de idade e da posição radial nas dimensões das fibras e dos vasos da madeira de Eucalyptus grandis Hill ex. Maiden

RESUMO – Objetivou-se neste trabalho avaliar a variacao das dimensoes das fibras e dos vasos da madeira de Eucalyptus grandis com quatro diferentes idades (10, 14, 20 e 25 anos), proveniente de talhoes comerciais. A amostragem do material na arvore foi feita atraves da coleta de tres discos, retirados da base e das extremidades das duas primeiras toras, ambas com o comprimento comercial de 3 m. De cada disco, retiraram-se cinco amostras, de dimensoes 1,0 x 1,0 x 1,0 cm, tomadas de pontos equidistantes, correspondentes a 0; 25; 50; 75; e 100% da secao, no sentido radial medula-casca, fazendo-se a medicao das fibras e dos vasos. Verificouse, em todos os parâmetros, o efeito da idade e da variacao radial, no sentido medula-casca, a excecao da largura e do diâmetro do lume das fibras; todos os demais parâmetros apresentaram correlacao positiva.

Resistência natural da madeira de Tectona grandis em ensaio de laboratório

This research aimed to evaluate the natural resistance of teak wood (Tectona grandis) to xylophagous fungi and termites in laboratory conditions. It was used trees with fifteen years old, from a plantation of the Forest Enterprise Celulose Nipo Brasileira - CENIBRA S.A., located in Belo Oriente, Minas Gerais State, Brazil. To determine the natural resistance of teak wood in laboratory were employed the Postia placenta, Neolentinus lepideus, Polyporus fumosus and Fomes connatus fungi and to termites resistance was employed the feeding preference assay with subterranean termites Nasutitermes sp. Samples were taken from four positions in the stem (heartwood near the pith, heartwood intermediate, outer heartwood and sapwood) at 1,30m to soil level and submitted to the action of fungi for thirteen weeks and termites for 45 days. It was found that the heartwood of teakwood from the Vale do Rio Doce, Minas Gerais State, Brazil was highly resistant. The internal heartwood was less resistant than the other portions of the heartwood to action of wood decay agents, while the sapwood was classified as moderately resistant (Polyporus fumosus) or resistant (Postia placenta and Neolentinus lepideus).

Influência da idade e da posição radial na flexão estática da madeira de Eucalyptus grandis Hill ex. Maiden

The objective of this work was to study the static bending variation of Eucalyptus grandis wood along the radial plane at four different ages (10 _ 14 20 and 25 years), from commercial stands. The samples were removed from a diametrical board on each of sixteen trees (four from each age); taken from four equidistant positions (0, 33, 66 and 100%), in the pith-to-bark direction, with six replicates per position. It was found that the elasticity modulus (MOE) showed mean values of 129.230 kgf/cm2, and the rupture modulus (MOR) showed mean values of 854 kgf/cm2, both showing to be positively correlated with age and radial position in the pith-to-bark direction. The greatest values were obtained from twenty-year-old wood and located near the bark.