Thermal properties and morphology of blends of poly(ether imide) and polycarbonate

Blends of poly(ether imide) (PEI) and bisphenol-A polycarbonate (PC) have been investigated by differential scanning calorimetry, dynamic mechanical thermal analyzer, scanning electron microscopy, and transmission electron microscopy. Three different molecular weights of polycarbonate have been used in the PEI-PC blends. Blends were prepared by screw extrusion and solution casting with weight fractions of PEI in the blends varying from 0.90 to 0.10. From the measured glass transition temperature (T_g), the maximum decrease of T_g(PEI) is observed for 0.9 weight fraction PEI in the PEI-PC blends. In the study of the morphology, the size of minor component domains (about 0.1 to 0.3 μm) in the 90/10 PEI-PC blend is small compared to the size of minor component domains (about 0.2 to 2.0 μm) in the 10/90 PEI-PC blend. This morphological behavior is attributed mainly to the difference of viscosity ratio between the dispersed phase and continuous phase. No considerable differences in the thermal behavior and morphologies have been observed among the blends of PEI and PC having different molecular weights.