Physical and mechanical properties of densified poplar by partial delignification

Physical and mechanical properties of wood can be significantly improved by densification process. Prior to densification, a pre-treatment should be adopted to soften the wood cell walls. Densified wood has a tendency to recover to its original dimensions, and thus a post-treatment can be adopted to improve its dimensional stability. In this study, a three-step process towards densified wood, i.e. alkali pre-treatment, hot compression and post-treatment, was used to fabricate the densified wood. To explore the suitable manufacturing parameters of the densified wood, poplar samples subjected to the alkali pre-treatment were compressed along the radial direction at 100 degrees C to the target thickness and then maintained at 100 degrees C for 24 h, or at 150 degrees C to the target thickness and then maintained at 150 degrees C for one hour. Some physical and mechanical properties of the densified poplar were compared to evaluate the effects of the densification process. The tensile and compressive strengths, modulus of elasticity and modulus of rupture had no significant differences for the adopted two densification processes. Both densification processes strongly reduced the set-recovery, but the densification process at 150 degrees C decreased the density and ductility of the densified poplar.