THE USE OF A MIXED COUPLING AGENT SYSTEM TO IMPROVE THE PERFORMANCE OF POLYPROPYLENE-BASED COMPOSITES REINFORCED WITH SHORT-GLASS-FIBER MAT

In order to improve the mechanical properties of composites consisting of polypropylene reinforced with mats of short glass fibres, the fibr e surface was treated with a silane coupling agent, N-beta(N-vinylbenz ylaminoethyl)-gamma-aminopropyl trimethoxy silane hydrogen chloride (S TS), and a titanate coupling agent, isopropltriisostearoyl titanate (T TS). The flexural properties and the impact absorption energy of these composites were measured as a function of coupling agent concentratio n. STS-only treatment of the fibre surface enhanced the flexural stren gth and the flexural modulus of the composite, while TTS-only treatmen t decreased the flexural strength and the flexural modulus. The improv ed flexural properties of the composite brought about by the STS-only treatment were obtained at the cost of its impact absorption energy, w hereas TTS-only treatment showed the inverse characteristics. However, in a mixed coupling agent system, the impact absorption energy of the composite was improved without a reduction in the flexural properties . A morphological study of the fracture surfaces of the composite afte r impact testing, void content measurement and single-fibre fragmentat ion test were also carried out to understand the interfacial phenomena of the surface treated composites. (C) 1998 Elsevier Science Ltd. All rights reserved.