Thermal behavior, morphology, and the determination of the Flory–Huggins interaction parameter of polycarbonate–polystyrene blends

Blends of bisphenol‐A polycarbonate (PC) and polystyrene (PS) prepared by screw extrusion and solution casting have been investigated with weight fractions of PC in the blends varying from 0.95 to 0.05. From the measured glass transition temperatures ( T g ) and specific heat increments (Δ C p ) at the T g , the polystyrene appears to dissolve more in the PC phase than does the PC in the PS phase. The blend appears to be near eqilibrium under extrusion conditions so that the polymer–polymer interaction parameter of PC/PS blends was calculated and found to be 0.038±0.004 for extruded blends at 250°C. Scanning electron microscopy supports the conclusion that the compatibility increases more in the region of PS‐rich compositions than in the regions of PC‐rich compositions of the PC/PS blends.