Optimization of the Thermo Hygromechanical (THM) Process for Sugar Maple Wood Densification
Densified wood is a promising engineered wood product, especially for heavy duty applications. This study optimized the temperature and duration of the thermo hygromechanical (THM) densification process applied to sugar maple (Acer saccharum Marsh. wood. The response variables studied were compression set recovery and hardness. The THM densification process was performed at three temperatures (180degC, 200 degC, and 220 degC) densification times (450 s, 900 s, and 1350 s) and post treatment times (900 s, 1350 s, and 1800 s) Response surface methodology was used to analyze the impact of the three parameters. The effect of temperature on the density profile across thickness was also determined. The results suggested that the optimum densification conditions resulting in high hardness and low compression set recovery were obtained at a temperature of 180 degC, a densification time of 1004 s, and a post treatment time of 1445 s. Additionally, the density of the densified samples was relatively homogeneous across thickness, although it was dramatically increased compared with control samples. However, density did not increase linearly with temperature. A much higher weight loss occurred at 220 degC, resulting in a significant decrease in density and hardness, whereas little compression set recovery was observed for sugar maple densified at this temperature.