Compression-molded products based on wet ball-milled wood and effect of various preparation conditions

Abstract

This study prepared compression-molded products from ball-milled wood by thermally plasticizing lignin without adhesives or resins. Wet ball milling for 120 min produced smooth, creamy slurries. The resultant products were hot-pressed at 180 °C and exhibited a plastic-like glossy surface and a high Young’s modulus (7.9 GPa), which was attributed to an increased bonding area. However, hydrogen bond formation occurs more predominantly during wood molding than thermoplasticization of lignin, because a hydrophilic surface was formed on wood fragments after wet ball milling in water. In contrast, when wood powder was ball-milled in toluene, drying aggregation due to hydrogen bond formation hardly occurred probably because the hydrophobic regions were preferentially cleaved. In this case, the hot-pressed product at 180 °C was formed mostly through the bonding owing to the thermoplasticization of lignin. These results suggest that the choice of the solvent for the mechanical disintegration of wood allows for control of the wood fragment surface and can affect the properties of the molded products.