Chemical and Mechanical Properties Changes in Corymbia Citriodora Wood Submitted to Heat Treatment

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 <i>Corymbia citriodora</i> (Hook.) K.D. Hill & L.A.S. Johnson. The heat treatment was performed in a laboratorial electric furnace at 160, 180 and 200ºC, under inert atmosphere, using boards measuring 6 × 16 × 56 cm<SUP>3</SUP> 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<SUB>t0</SUB>) decreased from 36% up to 55%, respectively. The stiffness properties (MOE) increased about 12%, improved during thermal treatment.