Melt rheology and extrudate morphology studies of polystyrene/polybutadiene blends in the presence and absence of compatibilisers

Abstract

Melt rheology and extrudate morphology of polystyrene (PS)/polybutadiene (PB) blends were studied with special reference to the effect of blend ratio and two different types of compatibilisers, the random copolymers and block copolymers. Uncompatibilized blends had viscosities approximately intermediate between those of the component polymers. In the case of uncompatibilized blends both positive and negative deviation was observed in the viscosity-composition curve at different shear rate range studied. The viscosity of the compatibilized blend was found to increase when a few percent of block copolymer was added. However, at high concentrations of the compatibiliser, the viscosity values leveled off. This is due to interfacial saturation. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the block copolymer was added followed by a clear leveling off at higher concentration. However, the random copolymer was not an effective interface modifier in agreement with microscopy study. These experimental results supports the earlier investigations of solid state NMR studies on these blends.