Crystallization behavior and rheological properties of polycarbonate and polypropylene blends

Crystallization behavior and rheological properties of blends of bisphenol‐A polycarbonate (PC) and polypropylene (PP) prepared by screw extrusion have been investigated by differential scanning calorimetry (DSC), polarized‐light microscopy, scanning electron microscopy, and a Rheometrics Mechanical Spectrometer. In the study of thermal analysis of PC‐PP blends by DSC, double crystallization peaks were observed in the PC‐rich compositions. In the study of spherulite of 7/3 PC‐PP blend, large droplets (>25 μm) of PP were crystallized between 115°C and 105°C, and then small droplets (<10 μm) of PP were crystallized at about 90°C. This result is consistent with the double crystallization behavior such that heterogeneous and homogeneous nucleations have been observed at about 105°C and about 85°C, respectively, by DSC measurements. From the results of rheological properties of the PC‐PP blends, the storage modulus of the PC‐PP blends at low frequencies has larger value than that of the simple mixing rule. The elasticity increase from the simple mixing rule is consistent with the emulsion model for a dispersed system.