Walmir Marques de Menezes

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.

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.

Tratamentos térmicos e secagem da madeira serrada de uva-do-Japão

The purpose of this study was ascertaining the influence of heat treatments in the drying rate and wood quality of Japanese raisin tree (Hovenia dulcis Thunb.). In order to do so, four trees with 25 years and average diameter at breast height of 39.5 cm and an average commercial height of 10 m, were harvested and transformed into samples of 40 x 130 x 500 mm (thickness x width x length), and classified as to the radial and tangential orientation of the material. The treatments consisted of heating in water by 12 and 24 h at 85 oC, and freezing by 12 and 24 h at - 18 oC. Then, the lumber was subjected to drying at 75 °C in a forced convection greenhouse until reach 12% of final moisture content. The freezing and heating treatments have proven to be influential on the drying rate, since the first accelerated the drying process, whereas the other one decreased. The freezing treatment by 24 h with samples oriented in the tangential direction showed higher drying rate compared with the others. The treatments presented to be not significant for the reduction of the contractions in the samples related to width, thickness and length. However, the volumetric contraction was significantly higher in samples heated in water. The Hovenia dulcis wood did not show top or surface cracks in any of the treatments used in this study.