Development of high density polyethylene / rice husk composites

Abstract

This research aims to develop wood plastic composites (WPC) prepared from high density polyethylene (HDPE) and rice husk (RH) to be used as a substitution of solid wood. Investigation on the effects of RH contents, RH particle sizes and the maleic anhydride grafted polyethylene (MA-g-PE) on the mechanical, thermal and physical properties of the HDPE/RH composites was conducted. The contents of RH were varied at 10, 20, 30 and 40 % wt respectively. The RH was grinded and sieved to 75, 180, 250, 355 and 500 micron prior to the preparation of the HDPE/RH composites. The MA-g-PE was applied as a coupling agent at 1, 3, 5 and 7% by weight. The mechanical characterizations revealed that the increment of RH content led to an increase in the flexural, tensile and compressive modulus. This is because the RH possessed higher stiffness and modulus than the HDPE. But the tensile, flexural, compressive and impact strength were lowered due to the poor interfacial bonding between the HDPE and the RH. Furthermore, the RH particle sizes did not influence to the tensile, flexural and compressive properties. The HDPE/RH composites with larger RH particles yielded higher impact resistance. Thermal characterizations revealed that the melting temperature and the heat deflection temperature increased slightly with increasing RH contents. At high content of RH, the degradation temperature of the HDPE/RH composites was reduced and the amounts of solid residues were raised due to silica content and other inorganic compound in RH. The RH particle sizes did not influence the glass transition temperature, melting temperature, heat deflection temperature and degradation temperature of the HDPE/RH composites. The physical characterizations indicated the increment of both density and water absorption by raising the RH amount. The water absorption of the HDPE/RH composites induced darker color to the HDPE/RH WPC. The HDPE/RH composites with smaller RH appeared darker color than the larger ones. In addition, the utilization of MA-g-PE as coupling agent enhanced the interfacial adhesion between HDPE and RH, this initiated the higher mechanical properties and thermal stability of the HDPE/RH composites. With increasing in MA-g-PE contents, affected on the mechanical properties, the melting temperature, the heat deflection temperature and the degradation temperature of the HDPE/RH composites increased slightly, but it did not affect on the glass transition temperature.