Rheological properties and phase inversion of polypropylene and poly(styrene-co-acrylonitrile) blends

Extension and shear viscosities of polypropylene (PP) and poly(styrene-co-acrylonitrile) (SAN) were investigated by the advanced rheometric expansion system (ARES), capillary rheometer, and extension rheometer. Blends of PP and SAN were prepared by screw extrusion with weight fraction of PP in the blends from 0.9 to 0.10. Shear and transient extension viscosity ratios were used in the Utracki, Miles and Zurek, and Metelkin and Blekht models to obtain the weight fraction of phase inversion for the blends. For the Utracki model, the weight fraction of the phase inversion for PP in the PP/SAN blend was 0.32 and 0.46 for the shear viscosity and transient extension viscosity ratios, respectively. From scanning electronic microscopy, the phase inversion was in the region of 45/55 PP/SAN blends. When the transient extension viscosity ratio was applied in the Utracki model, phase inversion in the PP/SAN blend showed good agreement with morphological studies of the blends.