Morphology and mechanical properties of poly(propylene)/polystyrene blends compatibilized with polystyrene‐block‐poly(ethylene‐co‐propylene)

Compatibilizing effects of diblock copolymer polystyrene‐block‐poly(ethylene‐co‐propylene) (SEP) on the morphology and mechanical properties of immiscible blends of poly(propylene) (PP) and polystyrene (PS) were investigated. Notched impact strength, yield stress, elongation at yield and Young's modulus were determined as a function of different weight ratios of PP and PS and different amounts of added SEP as well. Scanning electron microscopy revealed a two‐phase morphology of PP/PS blends, which exhibit poor mechanical properties. Even 2,5 wt.‐% of SEP added to PP/PS blends can improve the notched impact strength and elongation at yield compared to non‐compatibilized PP/PS blends. 10 wt.‐% of SEP compatibilizer converted the brittle PP/PS blend to quite impactresistant polymeric material. Mechanical properties were improved because of the morphological changes and increased interfacial adhesion as a result of SEP localization between PP and PS phases. An analysis of yield stress data in terms of theoretical models showed that yield stress values of binary PP/PS blends can be predicted with Nielsen's model.