The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as the liquid phase permeability. No radial permeability was observed for either wood. The permeability of air and water through the sapwood of Eucalyptus grandis was greater than that through the sapwood of Eucalyptus citriodora. The permeability of neen oil preservative through the sapwood of Eucalyptus grandis was also greater than through the sapwood of E. Citradora, but the difference was not statistically significant. Scanning Electron Microscopy images showed that the distribution and obstruction in the vessels could be correlated with observed permeability properties. Irrespective of the causes of differences in permeability between the species, the fluid phase flux through the sapwood of both species was significant, indicating that both Eucalyptus grandis and Eucalyptus citriodora could be successfully treated with wood preservative.

Efeito do tratamento térmico nas propriedades químicas, físicas e mecânicas em elementos estruturais de Eucalipto citriodora e Pinus taedaEucalipto citriodora quando ela foi exposta ao ataque de cupins subterrâneos Nasutitermes sp., de acordo com os ensaios de alimentação forçada, e das madeiras de E. citriodora e Pinus taeda, quando expostas ao fungo de podridão mole (Paecilomyces variotti).Palavras-chave: Madeira, termorretificação, análise química, propriedades físicas e mecânicas, durabilidade, resistência e rigidez, pínus e eucalipto.

The aim of this work was the evaluation of the thermal-rectification process of reforestation wood Corymbia citriodora Hook by measuring of mechanical properties under compression parallel to the grain and also determining of chemical composition. The tested samples were thermally treated in a furnace with nitrogen-atmosphere at heating rate of 0.033 °C.min -1 , at temperatures of 160, 180, 200, 220 and 240 °C. The chemical components and mechanical properties were affected with the thermal rectification process. The contents ranged from 17.85 to 3.51% extractives, 30.44 to 53.86% lignin, 69.56 to 46.14% holocellulose and 0.31 to 0.47% ashes. The samples strength decreased from 20% to 50% and the elasticity modulus increased about 47%. The characteristic values of strength under compression were determined and these changes were about 23% lower than Brazilian standard. The best mechanical properties of Corymbia citriodora were obtained at 180 °C.

No abstract

The heat is important treatment in the wood processing. The changes are not significant in structural properties in some case, like wood drying. However, in other treatments, such heat treatment and carbonization the changes can be intense. The main purpose of this research is to investigate the influence of thermorectification process on the chemical and mechanical behavior of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson. The heat treatment was performed in a laboratorial electric furnace at 160, 180 and 200 ºC, under inert atmosphere, using boards measuring 6 × 16 × 56 cm 3 and the temperature in the wood pieces was controlled by thermocouples. The mechanical and chemical properties were determined to fresh and heat-treated wood. The mechanical properties were evaluated by Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) in bending, and also tensile and shear strength parallel to the grain. The content of cellulose, hemicelluloses, lignin, extractives and ash were determined according to TAPPI Standard. The chemical analysis revealed that when the temperatures and time increase, the changes are ranged from 17.8 to 9.6% extractives; 30.4 to 44% lignin; 30.8 to 42.8% cellulose and 21.7 to 6% hemicelluloses. The ash content remains almost steady for all boards. The mechanical tests showed that the MOR and the tension parallel to the grain (f t0 ) decreased from 36% up to 55%, respectively. The stiffness properties (MOE) increased about 12%, improved during thermal treatment.