Oil uptake by wood during heat-treatment and post-treatment cooling, and effects on wood dimensional stability

Weight percentage gain (WPG), hydrophobicity and dimensional stability of Pinus radiata wood were examined after being heat-treated in raw linseed oil and left to cool in oil for 0 to 12 hours. The oil uptake percentage (OUP) in treated wood was determined after organic solvent extraction and compared with the weight percentage gain which was determined by difference in sample oven-dry weight before and after heat treatment. The effect of solvent extraction on hydrophobicity of treated wood was also examined. The results show that WPG in wood increased significantly with increasing cooling times which in turn decreased the water absorption. However, comparatively, dimensional stability in treated wood was less affected by increased WPG as a result of the prolonged cooling time. The oil uptake percentages determined after organic solvent extraction were greater than the weight percentage gain determined by weighing after heat-treatment, indicating mass loss with the heat-treatment. The moisture excluding efficiency (MEE) of the heat-treated wood decreased with solvent extraction showing the influence of oil uptake on hydrophobicity of wood.