Effect of thermal modification on the properties of exotic woods from commercial plantations

Abstract

Heat can be used to improve some properties of wood. Therefore, the goal of this work was to verify the effects of heat on the physical and mechanical properties of the species Pinus caribaea var. caribaea, Khaya ivorensis and Corymbia citriodora and checking for imperfections after exposition to humidity. To this end, the material was processed at temperatures of 160, 180 and 200 ºC, besides a reference sample. Then, samples’ physical properties, apparent density, equilibrium humidity, water absorption rate and shrink ability were evaluated. Janka hardness was the mechanical property analyzed. The woods were affected in different ways regarding physical properties. The apparent density changed at a temperature equal or higher than 180 ºC, while the equilibrium moisture content at temperatures equal or higher than 160 ºC. Retraction was altered after treatments at 180 ºC, while for Corymbia citriodora, it was changed from 160 ºC. The water absorption rate was only affected by heat treatment of hardwoods. Visible cracks were only noted in Corymbia citriodora wood, especially in tangentially cut samples. Wood hardness increased at a temperature of 160 ºC, exception for Corymbia citriodora due to the effect of cracking.

Keywords
Janka hardness; Cracking; Dimensional stability; Quarter sawn