Improving the mechanical properties of glass-fibre-reinforced polyester composites by modification of fibre surface

Polyalkenyl-poly-maleic-anhydride-ester/amide type new experimental additives have been developed and used to achieve the better properties of glass-fibre-reinforced polyester composites. Two different commercial reinforcements have been investigated: a chopped glass fibre and a glass woven [0/90°] fabric materials. Based on their chemical structures, both were E-type. The surfaces of reinforcements have been treated with the dissolved form of polyalkenyl-poly-maleic-anhydride-ester, polyalkenyl-poly-maleic-anhydride-amide and polyalkenyl-poly-maleic-anhydride-ester-amide type experimental coupling additives then they have been used in fibre-reinforced thermoset. The coupling additives have had differences not only in their chemical structure and physical properties, but also in the fibre–matrix interaction that can also be affected by them. That is the reason why additives have resulted in numerous differences in the mechanical properties of the reinforced specimens. The most favourable effects have been found in the case when the glass-fibre surface was modified by polyalkenyl-poly-maleic-anhydride-ester-amide type additives. Moreover, results have referred to more favourable effects in case of chopped glass-fibre mat than in glass woven fabric composites. Tensile properties could be improved by 38.9% with that additive and flexure properties with 21.9% in those laminates. Tensile and flexure properties of glass woven [0/90°] fabric reinforced composites could be improved by 18.0%, and 40.1% comparing to the untreated glass fibres containing polyester composites with the same reinforcement. The polyalkenyl-poly-maleic-anhydride-ester type surface modifying additive has deteriorated the tensile and flexural properties of the laminates, but the dynamic properties have been more favourable than those of specimens with untreated glass fibres. Fibre–matrix interaction responsible for increased or decreased mechanical properties has been studied on SEM micrographs of the fractured face of composites. It has been found that the unfavourable results had been caused by the fibre slipping out the polyester matrix. Nevertheless, it has been supported by visual observation that the polyalkenyl-poly-maleic-anhydride-ester-amide additive managed to improve the adhesion between the fibres and the matrix.