Effect of pressing parameters on dimensional stability and bonding performance of thermally compressed coconut wood

Previous research on thermally compressed (TC) coconut wood has shown potential for structural applications. However, its dimensional stability needed to be improved. This study aimed to improve the dimensional stability of TC coconut wood for further use in laminated products by using relatively high pressing temperatures to make it more hydrophobic. TC specimens with a target compression ratio of 55 % were manufactured from low-density (LD, 332 +/- 25 kg/m3) wood, and TC specimens with a target compression ratio of 25 % were manufactured from medium-density (MD, 514 +/- 28 kg/m3) wood. Two pressing temperatures (170 degrees C and 200 degrees C) and three pressing times (1 h, 2 h and 3 h) were applied. Chemical changes, dimensional stability, physical and mechanical properties, and bonding performance of the specimens were examined. Thermal degradation of the LD specimens was higher than that of the MD specimens. Differences in chemistry between the surface and the interior could explain bonding behavior. Pressing temperature had a greater impact on wood degradation than the pressing time. Dimensional stability could be achieved at 200 degrees C pressing temperature. Most physical and mechanical properties of the TC specimens had decreased due to thermal degradation. However, compressive strength parallel to the grain and modulus of elasticity were not affected at the chosen pressing parameters. Bonding performance determined by block shear tests was dependent on the original material, panel assembly, and the sanding process. Longitudinally laminated panels made from MD specimens with sanded surfaces provided the highest block shear strength.