Mechanical, thermal and electrical properties of epoxy modified with a reactive hydroxyl-terminated polystyrene-butadiene liquid rubber

Abstract

This study investigated the modification of epoxy resin with a hydroxyl-terminated polystyrene-butadiene liquid rubber copolymer. The Fourier transform infrared analysis evidenced the occurrence of a chemical reaction between the oxirane ring of epoxy resin and the hydroxyl functional group of hydroxyl-terminated polystyrene-butadiene using benzyldimethylamine as a catalyst. The mechanical results indicated that the 10 phr hydroxyl-terminated polystyrene-butadiene-modified epoxy resin exhibited the maximum impact strength of 16.5 J/m2, which is about 91.8% higher than that for the neat epoxy; the best mechanical performance in terms of tensile and flexural properties was achieved at 10 phr hydroxyl-terminated polystyrene-butadiene content; higher concentration of hydroxyl-terminated polystyrene-butadiene resulted in the cured networks lower impact and strength values. The investigation on the microstructure of hydroxyl-terminated polystyrene-butadiene–modified epoxy resin showed a two-phase morphology where the hydroxyl-terminated polystyrene-butadiene domains were uniformly dispersed in epoxy resin matrix. The addition of hydroxyl-terminated polystyrene-butadiene into epoxy resin reduced the thermal stability, whereas, it obviously improved the volume, surface resistivity; and the dielectric breakdown strength of 20 phr hydroxyl-terminated polystyrene-butadiene–modified epoxy resin was 36 kV/mm compared to 31.2 kV/mm of the neat epoxy resin.