Chemical resistance of polystyrene/polypropylene blends: effect of blend compositions and SEBS content

Abstract

Polystyrene (PS) is widely used in packaging, building and construction, and injection molding application due the advantages of being clear, hard, easily processed and low cost. However PS lack in toughness and chemical resistance towards certain chemical such as ketones. Blends of PS with Polypropylene (PP) are developed with the objective to enhance the impact and chemical resistance of PS. However, the blends of PS and PP are known to be immiscible and incompatible. Previous studies have concluded that the block copolymer such as styrene-b-(ethylene-co-butylenes)-b-styrene (SEBS) is good compatibilizer for this PS/PP blends. The present study investigates the effect of SEBS on the chemical resistance on the PS/PP blends. Using a Brabender PL2000 twin-screw extruder, blends of PS/PP in various composition ranging of 90-60 wt % PS containing different amount of SEBS in the composition range of 5-25 phr were prepared and injection molded to evaluated for chemical resistance. The chemical resistance testing was carried out according to ASTM D543-87. The specimens were placed in appropriate containers for the reagents being used, and allow the specimens to be totally immersed in fresh reagent for 7 days in the Standard Laboratory Atmosphere. The results show the chemical resistance of PS to acetone (ketone) increases with increasing PP content. On the other hand, the chemical resistance of PS/PP blends increases with increasing SEBS content at lower PP content. However, at higher PP content, the chemical resistance decreases with increasing SEBS content.