Effect of surface treatment of natural reinforcement on thermal and mechanical properties of vinyl ester/polyurethane interpenetrating polymer network-based biocomposites

Kenaf fibre-reinforced vinyl ester (VE)/polyurethane (PU) interpenetrating polymer network (IPN)-based composites were made by hand lay-up technique. The kenaf bast fibre was chemically treated with 3, 6 and 9% vinyl silane. Treated fibres were characterized in terms of crystallinity, mechanical strength, density, thermal property and morphology. In comparison with the untreated fibre, 6% silane-treated fibres showed 25.4% higher % crystallinity, 66.9% increase in modulus elasticity and 604.2% increase in tenacity. Comparison of the pure VE with VE/PU IPN showed that the IPN had 3.3% lower modulus but 26.4% higher toughness than the former. Composites based on pure VE matrix and VE/PU IPN matrix were manufactured with the variation of untreated and treated fibre loading as 15, 20, 25, 30, 35 and 40 wt%. Novelty of this work lies in the modification of both the fibre surface and the matrix system simultaneously with the aim of increasing the adhesion between the fibre surface and matrix material of the composite. Composites with untreated fibres showed poor strength compared to that with modified fibres having corresponding compositions. IPN-based composites, with 35 wt% silane-treated fibre, showed improvement in tensile modulus by 16.61% and flexural modulus by 6.35% than pure VE-based composites with corresponding fibre loading.