Blends of polycarbonate and poly(methyl methacrylate) and the determination of the polymer-polymer interaction parameter of the two polymers

Blends of bisphenol A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) prepared by screw extrusion and solution casting have been investigated by differential scanning calorimetry and scanning electron microscopy. From the measured glass transition temperatures (T sub g ) and specific heat increments ( Delta C sub p ) at the T sub g , the PMMA appears to dissolve more in the PC-rich phase than does the PC in the PMMA-rich phase. The blend appears to be near equilibrium under extrusion and solution-casting conditions so that the Flory--Huggins interaction parameter between PC and PMMA was calculated and found to be 0.039 plus/minus 0.004 for extruded blends at 250 deg C and 0.043 plus/minus 0.004 for solution-cast blends at 25 deg C. Scanning electron microscopy supports the conclusion that the compatibility increases more in the PMMA-rich compositions than in the PC-rich compositions of the PC/PMMA blends. 51 ref.--AA