Properties of blends of polycarbonate and polypropylene (I): Crystallization behavior

Blends of polycarbonate (PC) and polypropylene (PP) have been investigated by differential scanning calorimetry and polarized-light microscopy. From the measured melting temperature (T_m) of the PC-PP blends, it appears that the values of T_m of PP in the blends are shown to almost unchanged compare to that of the unblended PP. In the PC-PP blends, double crystallization peak are observed at about 80 °C and 100 °C when the PP becomes dispersed phase. This result indicates that the nucleation of PP in the PC-PP blends is divided into two parts: heterogeneous nucleation and homogeneous nucleation. For the blends of PC and PP with styrene-ethylene-butylene-styrene triblock copolymer (SEBS), the SEBS acts as a heterogeneous nucleating agent, thus a single crystallization peak is observed at about 100 °C. In the study of morphology of PC-rich composition, it was found that the spherulite size was decreased when the crystallization temperature was about 80 °C compare to the crystallization temperature was about 100 °C. This result is consistent with the double crystallization behavior of PP. From the above results, it is suggested that the nucleation of PP in the PC-rich composition is divided into two parts with the type of the dispersion and the size of the dispersed phase. From the measured crystallization temperature of PP in the blends, the interfacial free energy between the heterogeneous nuclei and the PP of the blends.