Production of Complicated Shape Cups by Injection Molding of Several Wood Biomasses

Applications of biomass-based materials have drawn attentions as a future material technology due to the green as well as the sustainable developments. Wood biomasses have a great abundance on the earth, and many studies aiming at an industrial use of wood biomass have been done by means of the physical and the chemical processing. Our previous study showed that untreated various biomasses including solid woods got improved fluidity under a temperature range from 160 to 180 °C with a moderate moisture condition, and injection-molded products could be obtained with a comparatively high density and hardness than the raw material. In this study, the injection molding of several wood biomasses, namely solid Japanese cedar, bamboo and rice straw, were performed to investigate the possibility and problems in the production of an industrial applicable material. Furthermore a pre-treatment of wood biomass by steaming was conducted as a preliminary trial to improve the injectability and the mechanical and physical properties of the products. The results showed that there might exist optimum conditions among the mold temperature and the mold nozzle size for wood biomasses with a given moisture level to make a complicated shape cup. The injected products showed average hardness of about 19HV (cedar), 24HV (bamboo) and 13HV (rice straw) with above 1.35 g/cm3 of the bulk densities. It was found that the pre-treatment by steaming of the wood biomasses was effective at decreasing pressure required for the injection molding, and attained the products with improved size stability against water.