Morphology control and interfacial reinforcement in reactive polystyrene/amorphous polyamide blends

Abstract

The effects of reactive compatibilization on blend morphology and interfacial adhesion in the polystyrene (PS)/amorphous polyamide (aPA) system were investigated. Reactivity was incorporated onto the polystyrene component by copolymerization with ∼1% of vinyl oxazoline which is reactive with the amorphous polyamide end-groups. The reaction between oxazoline and polyamide end-groups produces interchain bonds and the in situ generation of copolymers. Incorporation of reactivity into this system has resulted in significant refinement of the blend morphology, with the dispersed phase size in the reactive blend reduced by ∼60% relative to the unreactive blend. The grafting reaction was verified and quantified using infra-red spectroscopy, which indicated that ∼2.5 wt% of PS- g-aPA compatibilizer was formed during blend processing. In addition to stabilizing the microstructure, in situ compatibilization was found to alter the mechanical properties of the PS/aPA interface. Evaluation of adhesion at both the reactive interface and its unreactive counterpart revealed that the reactive interface was mechanically reinforced by copolymer formation, and typically showed fracture toughness at least twice that of the unreactive interface.