Properties of rice husk‐HDPE composites after exposure to thermo‐treatment

Natural fiber reinforced thermo‐plastic composite, with its often‐excellent properties, is well known as a material for external flooring and landscaping. Thermo‐treatment is considered as a method to improve the mechanical properties of these composites; however, oxidation might occur. In this article, thermo‐treatment is applied to a rice husk reinforced high density polyethylene (RH‐HDPE) composite. Variations in the mechanical properties, color, mass, and chemical constituents of the RH‐HDPE composite after thermo‐treatment were investigated. The results indicated that, with the extension of thermo‐treatment time, the color of the composites darkened; the composites underwent a gradual mass loss; during the early stages of thermo‐treatment the composite's flexural properties increased, and then remained stable after 128 h of treatment. Fourier transform infrared (FTIR) spectroscopy analysis showed wood indices of the RH‐HDPE composite decreased, indicating thermo‐degradation occurred during thermo‐treatment. Wide angle X‐ray diffraction (WAXD) results indicated an increased crystallinity of the RH‐HDPE composite in the first 128 h of thermo‐treatment, and increased crystalline grain size in the first 64 h of thermo‐treatment. Appropriate thermo‐treatment is essential to improve the mechanical properties of RH‐HDPE composites. POLYM. COMPOS., 35:2180–2186, 2014. © 2014 Society of Plastics Engineers