Investigation on the effect of alkali treatment of the rice straw on mechanical properties of rice straw flour-polypropylene composites

In this study, the effect of alkali treatment on the mechanical properties of rice straw flour- polypropylene composite was investigated. Rice straw flour (40 mesh) was treated with hydroxide sodium 5 and 10% in two times, once for 45 and another time for90 min respectively. The composites were made from rice straw flour as filler (30%), polypropylene (65%) as matrix and maleic anhydride (5%) as coupling agent. In order to blend the raw materials of internal mixer a Haake HBI system 90 machines and make standard samples testing an injection molding were applied. The results of this study suggest that treatment of rice straw flour with alkali 5% concentration increases tensile modulus and impact strength which increase with time prolongation. However, treatment of rice straw flour with alkali 10% concentration decreases these properties even with the increasing of time. Furthermore, the increasing of alkali concentration and treatment time resulted in an increase in the tensile strength of composites.