Effect of density on the hygroscopicity and surface characteristics of hybrid poplar compreg

The objective of this study is to investigate the relevance of hybrid poplar compreg density and its physical properties and surface characteristics, such as hygroscopicity, dimensional stability, wettability, roughness, surface energy, and porosity. The different desired densities (ranging from 0.6 to 1.2 g/cm(3)) of compreg were achieved using manufacturing processes with various parameters. The results indicated that the water absorption decreased and dimensional stability improved with the density increasing in the range of this study. In addition, the density was contributed to the reduction of the wettability and the roughness of compreg. Furthermore, the evaluation of the surface energy showed that the total surface free energy declined significantly due to the densification process. The high density reduced the apertures present in the vessels and the fiber cells and, consequently, decreased the total porosity of compreg. This, in turn, impeded the penetration of moisture into compreg and reduced its hygroscopicity.