Effects of steam heat-treatment on properties of pinus massoniana wood and its bonding performance

Abstract

Pinus massoniana wood was modified by steam heat-treatment at 160°C, 180°C, 200°C and 220°C respectively and effects of the changes of density, pH, surface wettability and apparent morphology of Pinus massoniana heat-treated wood on its bonding performance were studied in this paper. The results showed that Pinus massoniana wood underwent a series of physical and chemical changes during heat-treatment as the the following: (1) The degradation of hemicellulose and cellulose with low degree of polymerization, degradation and migration of the extract resulting in the decline of density and pH of heat-treated Pinus massoniana wood. (2) Brittle fracture occured on the cell wall surface, and the pit collapse, shrink and deformation, resulting in the formation of roughness and porosity on the wood surface. (3) The surface energy decreased with the improvement of temperature, the surface wettability of Pinus massoniana wood treated at 160°C–180°C was good, while that at 200°C– 220°C showed hydrophobicity. (4) Changes of density, pH, surface roughness and porosity, and wettability resulted in a reduction in the bonding strength and reliability of heat-treated Pinus massoniana wood with MUF resin adhesive. (5) When the temperature was at 160°C–180°C, the better wettability of heat-treated Pinus massoniana wood could guarantee the better bonding performance.