Localization of styrene-butadiene block copolymers in polystyrene/polypropylene blends

Structure of polystyrene/polypropylene, PS/PP, blends compatibilized by styrene-butadiene and styrene-butadiene-styrene block copolymers was studied by small-angle X-ray scattering and transmission electron microscopy. The results are compared with those obtained previously for a similar blend (HIPS/PP) where the PS phase contains polybutadiene, PB, inclusions. It is shown that the triblock influences formation of interfacial layer in both blends in much more pronounced way than the diblock. This results in improvement of impact strength and elongation at break in the blends compatibilized by the triblock copolymer. In HIPS/PP blends, PB inclusions have no influence on the compatibilization efficiency of both block copolymers but they improve mechanical properties due to the toughness modifier action of PB in the PS phase.