Joel Telles de Souza

Qualidade da madeira serrada proveniente de árvores dominantes e médias de Eucalyptus grandis submetidas à secagem

Neste estudo, objetivou-se verificar, em arvores de diâmetro dominante e medio, a influencia da secagem ao ar livre e secagem convencional na qualidade da madeira serrada de um povoamento de Eucalyptus grandis W. Hill ex Maiden, aos 14 anos de idade, situado no municipio de Capivari do Sul, Rio Grande do Sul. Para tanto, a amostragem das arvores foi realizada apos um inventario piloto, tendo como base o diâmetro a altura do peito (DAP) dominante e medio. Apos a derrubada, foi retirada a tora localizada entre as posicoes DAP e 25% da altura comercial. As toras foram desdobradas em tabuas para serem submetidas a secagem ao ar livre ate 18% do teor de umidade, e a secagem convencional foi conduzida ate 13% de umidade. Rachaduras de topo e arqueamento das tabuas foram avaliadas apos o desdobro, na secagem ao ar livre e na secagem convencional. Os resultados mostraram que, tanto para as arvores dominantes quanto para as medias, o indice de rachaduras de topo e a flecha de arqueamento das tabuas nao diferem significativamente nas diferentes fases de processamento da madeira. No entanto, a comparacao entre esses dois estratos evidencia que a magnitude desse defeito e mais pronunciada nas arvores medias.

Modificação térmica nas propriedades físicas da madeira

The objective of this research was to evaluate the effect of thermal change in the physical properties of wood Corymbia citriodora and Eucalyptus saligna, compared with the control (untreated wood). For that were sampled three trees of each species, with approximately 40 years of age, which were taken the first two logs 3 feet long. The thermal modification of wood was conducted by employing final temperature of 140°C, 160°C and 180°C for 2.5 hours, over the control (no treatment) using an oven with forced air circulation. Tests of physical properties were performed according to established procedures in ASTM and adaptations (ASTM 143-94, 2000), and consisted in evaluating the equilibrium moisture content, weight loss, swelling coefficient of total (linear and volumetric) and coefficient anisotropy. Overall, the results showed that the thermal modification was effective in reducing the moisture balance, weight loss, decrease in swelling and total anisotropy coefficient of both species, with the higher values observed in the treatments of higher temperatures.

Combinação de dois métodos não industriais no tratamento preservativo de moirões de Eucalyptus grandis

This paper evaluated the effect of the combination of two non-industrial methods to treat fence posts of Eucalyptus grandis , on the penetration and retention of water borne preservative. Thus, four fences with 2.20 m in length were treated by replacement of sap and simple diffusion alone and other four ones have combined the two techniques, with water-borne CCB 50% preservative at a concentration of 3.5%. After each treatment condition, the pieces were seasoned in the shade for 30 days. Disks were taken at 0.60 and 1.60 m from the base of the pieces which had one side sanded for analysis of the penetration of the preservative using a solution of chrome azurol S. From the same parts, test specimens were also manufactured in diametrically opposed positions with dimensions of approximately 3.0 x 2.0 x 2.5 cm (radial x tangential x longitudinal) to analyze the retention of the element copper by atomic absorption spectrophotometry method and boron by visible spectrophotometry with azomethine-H, also known as colorimetry. The retention values obtained were compared with the minimum recommended by the Brazilian Association of Technical Standards – ABNT for water borne preservatives which is 6.5 kg of active ingredients per m³ of wood. The penetration achieved by the combined method was considered sufficient for non-industrial treatment, while the retention values were higher than the retention of at least 6.5 kg of active ingredients / m³ of treated wood in all positions and portions evaluated.

Efeito do desbaste no comprimento das fibras da madeira de Eucalyptus grandis W. Hill ex Maiden

Este estudo teve como objetivo avaliar o efeito do desbaste no comprimento das fibras da madeira de Eucalyptus grandis aos 18 anos de idade. Para tanto, foi analisado um experimento situado proximo ao litoral do Rio Grande do Sul, instalado em delineamento de blocos ao acaso com quatro repeticoes. Os tratamentos foram definidos devido ao numero de desbastes aplicados e variaram de zero ate seis intervencoes. As arvores foram selecionadas, em cada tratamento, com base no diâmetro dominante de Assmann e no diâmetro da arvore central, sendo denominadas de arvores dominantes e centrais, respectivamente. Apos o abate, no disco correspondente a regiao do DAP (diâmetro a altura do peito) foram marcadas e seccionadas baguetas centrais de onde se confeccionaram fragmentos selecionados em intervalos regulares, no sentido medula-casca, para maceracao. Os resultados indicaram que o desbaste influenciou o comprimento das fibras das arvores dominantes e centrais, porem, nao foi verificada uma tendencia sistematica de acrescimo ou decrescimo dessa estrutura em funcao do espaco vital utilizado. Independentemente do estrato dominante ou medio, o comprimento das fibras apresentou um padrao de variacao crescente no sentido medula-casca em todas as intensidades de desbaste analisadas e os menores valores foram observados proximos a medula.

USO DE Bambusa tuldoides E Eucalyptus grandis PARA CONFECÇÃO DE PAINÉIS AGLOMERADOS

The bamboo panels particleboards can be advantageous when produced with a mixture of some kinds of wood. However, there are few studies using Bambusa tuldoides for the production of homogeneous particleboards or in combination with wood particles. Therefore, the aim of this study was to evaluate the physical-mechanical quality of particleboard made of different percentages of B ambusa tuldoides and E ucalyptus grandis . To do so, 36 panels were produced composed of a mixture of 0, 25, 50, 75 and 100% of dry matter. The tests realized were moisture, mass density, swelling thickness and water absorption. The mechanical tests were bending, internal bond and screw withdrawal (ASTM 1037, 1999). The results submitted to the correlation test and analyzed by regression. The panels did not get the minimum values of the standards (ANSI A 208.1, 1987) for mechanical tests. It is concluded that the homogeneous bamboo panels obtained superior performance in physical tests than the eucalyptus panels, which are usually used in the industrial sector. However, the insertion of bamboo particles impaired the performance of the panels in the mechanical tests.

AVALIAÇÃO DAS PROPRIEDADES FÍSICO-MECÂNICAS DE PAINÉIS DE CASCA DE ARROZ E ADESIVO TANINO-FORMALDEÍDO

Rice husk, waste produced by processing of rice, has become a problem of environmental, economic and public health. As a result, this research aims to explore the potential of these underutilized resources in Brazil in the development of particleboard glued with tannin-formaldehyde. Therefore, panels were manufactured with rice husk compacted at different density (0.65, 0.95 and 1.15 g/ cm³), levels of adhesives (7, 10 and 13%) and particles types (natural and processed), totaling 54 panels. The pressing was carried in hydraulic press at 30 kgf /cm² for 8 minutes at 180°C of temperature. The physical tests performed were moisture content, density, water absorption and thickness swelling while mechanical properties evaluated were static bending, screw withdrawal and internal bond. In general, the use of rice hulls prouced a reduction in strength when compared to those made with wood particles. All particleboard were below the minimum standards in physical and mechanical properties; only the panels with 13% resin provided minimum values required by market standards regarding dimensional stability. The results indicate that the material cannot be used in conditions requiring great structural efforts.

Caracterização tecnológica da madeira de Eucalyptus benthamii Maiden et Cambage

The knowledge about the technological properties of the wood enables the achievement of tools that assist in the adequate use of this material. Therefore, the aim of this study was accomplish the technological characterization of Eucalyptus benthamii wood for potential uses. For this, it was used six trees of the forestry plantation implanted in the Guatambu city, Santa Catarina State, Brazil. For the physical characterization of the wood, discs were obtained at three different positions of the trunk of each tree, determining the basic density and retractibility. The test pieces to the mechanical tests of parallel compression to the fibers, dynamic bending, static bending and Janka hardness were obtained from discs removed of the logs. The average basic density was 0.549 g cm -3 , while the retractibility parameters were similar to those of genus eucalyptus, with an average anisotropy coefficient of 1.9, indicating that it is a specie unstable dimensionally. The results obtained from the mechanical tests show that the Eucalyptus benthamii wood has less resistant to mechanical stress, limiting its use for this purpose. Therefore, the application of this species for purposes applying mechanical stress is limited, making it necessary carrying out studies about the other properties of this wood.