Effect of SEBS on impact strength and flexural modulus of polystyrene/polypropylene blends

Abstract

Blends of Polystyrene (PS) with Polypropylene (PP) were developed with the objective to overcome the inherent brittleness of PS and enhance the impact strength at room temperature. However, the blends of PS and PP were known to be immiscible. Previous studies have concluded that the block copolymer such as styrene-b- (ethylene-co-butylenes)-b-styrene (SEBS) is good compatibiliser for this PS/PP blends. The present study investigates the use of SEBS as a compatibiliser in this immiscible blend system. Using a Brabender PL2000 twin-screw extruder, blends of PS/PP in various composition range of 90-60 wt% PS containing different amount of SEBS in the composition range of 5-25 phr were prepared and injection molded to evaluate for mechanical properties. The results obtained from mechanical properties show some improvement in the properties of the blends indicating some compatibilisation effect in the blend system. The addition of SEBS enhanced the impact properties of the blends but reduced the flexural strength and flexural modulus. The blends of 90/10 PS/PP with 25 phr SEBS gave superior impact properties. Interestingly, the results show that SEBS is more effective at lower PP content.