Performance Study of compact wood powder material processing for improved impact characteristics aiming at substitute for plastics

Abstract

Abstract Recently, a plastic-like material has been obtained by compression of wood powder only under an appropriate temperature and pressure conditions. It is considered that this change in a surface texture like transformation comes from auto-condensation of wood components. The static bending strength of the wood powder material (WPM) at 23 °C is roughly the same as that of plastics such as ABS, and due to the auto-condensation of wood components the WPM can be enhanced and hardened. These good outcomes mean that the WPM might be applied as a substitute material for plastic without using any petroleum-based adhesives. Such kinds of techniques have become very important for future material. To achieve utilization of the WPM for a plastic application, other properties such as impact characteristics must be investigated. Furthermore, an efficient processing of the WPM using vapor steaming should be developed to reduce processing energy. In this study, a new wood-based product aiming at an alternative material for plastics and its processing with vapor has been researched using wood powder only. Effects of production conditions, namely compression pressure, vapor steaming temperature, heat treatment time and size of wood powder, on the mechanical properties such as bulk density, impact bending strength, bending Young modulus and Charpy impact strength of the WPM were experimentally investigated, and feasibility and problems in the production of alternative material for plastics from wood powder were discussed. Results showed that the impact bending strength and Young modulus were improved with elevated vapor steaming temperature up to about 140 °C, and they level off above 150 °C. However, the Charpy impact strength only tends to be decreased above 150 °C. The impact characteristics of WPM are improved by increasing the compression pressure up to 30 MPa at constant vapor temperature of 160 °C. They are hardly changed when the pressure and temperature are applied for more than 5 min of the heat treatment time. The impact characteristics of the WPM have their maximums when the wood powder ranging roughly to 100 μm in size is compacted under the vapor steaming condition of 160 °C. In comparison of the impact characteristics among WPM and engineering plastics, WPM has the maximum Young modulus but has poorest Charpy impact strength. Therefore the Charpy impact strength of the WPM must be improved in our further study.