Short natural-fibre reinforced polyethylene and natural rubber composites: Effect of silane coupling agents and fibres loading

Composites materials based on cellulose fibres (raw or chemically modified) as reinforcing elements and thermoplastic matrices were prepared and characterized, in terms of mechanical performances, thermal properties and water absorbance behaviour. Four different cellulose fibres with different average lengths were used, namely avicel, technical, alfa pulps and pine fibres. Two thermoplastic polymers, i.e. low density polyethylene and natural rubber, were employed as matrices. Cellulose fibres were incorporated into the matrices, as such or after chemical surface modification involving three silane coupling agents, namely γ-methacryloxypropyltrimethoxy (MPS), γ-mercaptoproyltrimethoxy (MRPS) and hexadecyltrimethoxy-silanes (HDS). As expected, the mechanical properties of the composites increased with increasing the average fibre length and the composite materials prepared using both matrices and cellulose fibres treated with MPS and MRPS displayed good mechanical performances. On the other hand with HDS bearing merely aliphatic chain only a modest enhancement on composite properties is observed which was imputed to the incapacity of HDS to bring about covalent bonding with matrix.