Effect of coupling agents on the crystallinity and viscoelastic properties of composites of rice hull ash-filled polypropylene

Abstract

This paper focuses on the application of silica rich, rice hull ash (RHA) from the rice industry as filler in polypropylene (PP). The dynamic rheological behaviour and the crystallinity of its composites with semi-amorphous polypropylene were used as performance indicators. The effect of coupling agents on RHA/PP compatibility was also investigated. Addition of RHA increased storage modulus (G′), and the onset (Tco) and peak (Tc) crystallinity temperatures, and decreased the degree of crystallinity of the system. Two coupling agents, maleated polypropylene (MAPP) and an amino functional silane, were used to improve the interfacial adhesion of RHA and PP. Addition of MAPP increased G′, Tc and Tco and the crystalline phase of the system. Addition of silane had mixed effects. It increased the rheological properties at higher concentrations, it increased Tc and Tco at all the concentrations and increased crystallinity at lower concentrations and decreased it at higher concentrations. Results from a thermogravimetric analyser were useful in revealing the mechanism by which silane bond to RHA and its effect on the rheology and crystallisation behaviour of the composites.