Effect of Surface Treatment of Glass Fibres on Adhesion to Polypropylene Resin

This study concerns the treatment of glass fibres to improve their adhesion to polypropylene resin (PP). The glass fibres were treated with four types of coupling agents and then with maleic anhydride grafted polypropylene (MAPP) emulsion. The surface characteristics and bond strength were analyzed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS), and a microbonding pull-out test. The mechanical properties of the composites were tested. Because the two ends of the coupling agent molecules reacted with the glass fibre surface and the MAPP emulsion respectively to form chemical bonds, and the MAPP emulsion possesses good compatibility with polypropylene, an interphase was formed while melt blending, which improved the glass fibre/polypropylene bonding. This could be proved by using a microbonding pull-out test. The composites of glass fibre and PP were fabricated by means of a twin screw extruder and an injection moulding machine. The tensile strength and flexural strength were measured and the fracture surfaces were observed by SEM to assess the contribution of the surface treatment. The test results demonstrate that the tensile strength of those composites reinforced by glass fibres treated with coupling agent and MAPP emulsion was 38% higher than that of the composites reinforced by untreated glass fibres, and 21% higher than that of composites that used the coupling agent alone. As for the flexural strength, the coupling agent/MAPP emulsion treatment was 44% better than having no treatment and 25% better than using the coupling agent alone.