Effect of artificial weathering on the properties of heat treated wood

Abstract

This study aims to investigate the change in chemical composition, surface characteristic and mechanical properties of heat treated four wood species (ash, iroko, Scots pine and spruce) during artificial weathering from 400 h to 1600 h in relation to their color changes, surface roughness, compression strength, modulus of elasticity, modulus of rupture and surface composition. Original color of wood species was significantly changed by heat treatment and artificial weathering. Artificial weathering decreased color change of heat treated wood samples except for iroko. Color change significantly increased with longer weathering exposure for heat treated wood samples however similar trend was not observed for control samples exposed to weathering factors. In general, heat treatment alone did not have a considerable effect on surface roughness of wood. Heat treatment seemed to protect wood surface to become rougher after weathering for softwoods. Compression strength and MOR of samples decreased while MOE increased during heat treatment. Compression strength, MOR and MOE of samples decreased considerably with longer weathering exposure both for heat treated and control samples. Softwood species seemed to be more affected by heat and weathering than hardwood species did with respect of loss on the strength properties. Severe delignification and hemicellulose degradation occurred in heat treated and control samples for all wood species during weathering from 400 h to 1600 h evident from rapid decrease at 1504/1508 cm−1 and 1730 cm−1, respectively. Heat treatment did not fully protect hemicellulose degradation and delignification occurred by weathering with longer exposure periods.