Use of rice husk ash in thermoplastic composites

Abstract

The purposes of this research are to develop the wood plastic composites (WPC) from poly(vinyl chloride) (PVC) and rice husk ash (RHA) as an alternative material substituting natural wood, and also to investigate the effects of particle sizes and the amount of RHA on the mechanical, thermal and physical properties of PVC/RHA composites. In this study, RHA was used as a filler. Rich in silica content, RHA was deemed an appropriate filler for WPC. RHA was grinded to particle sizes of 45, 75, 106, 180 and 250 μm and blended with PVC compound at 20, 40, 60 and 80 phr. Experimental results showed that the tensile, flexural and compressive modulus and compressive strength of the PVC/RHA composites increased with increasing in RHA contents. Both the tensile and the flexural strengths of the PVC/RHA composites tend to decrease with increasing RHA contents. This is due to the poor interfacial adhesion between the PVC and the RHA. With greater RHA contents, the impact energy decreased because the toughness of the PVC/RHA composites was decreased. For the thermal properties, the heat deflection temperature (HDT) and the glass transition temperature (Tg) of the PVC/RHA composites increased slightly with increasing RHA contents. This is because the RHA particles hindered the mobility of the PVC molecules. RHA had no significant effect on the decomposition temperature (Td) of the PVC/RHA composites. Upon degradation, the residual solid weight of the PVC/RHA composites increased with greater RHA contents. The density and the rate of water absorption of the PVC/RHA composites also increased with higher RHA contents. With 20 phr, the PVC/RHA composites were dark grey in color. Further increase of the RHA content led to a change of color from dark grey to black. The particle sizes of the RHA had no significant effects on the modulus and strength under tensile, flexural and compressive stresses, the HDT, Tg, Td, the density and the rate of water absorption while the impact energy increased with larger RHA particles. The small RHA particles yielded composites with a darker shade than those with larger RHA particles.