Crystallization behavior of poly(trimethylene terephthalate)/polycarbonate blends

The crystallization behavior of poly(trimethylene terephthalate (PTT) in compatibilized and uncompatibilized PTT/polycarbonate (PC) blends are investigated in the research reported in this paper. The differential scanning calorimetry (DSC) results showed that the crystallization behaviors of PTT/PC blends were very sensitive to PC content. The onset (T-ci) and the peak (T-c) crystallization temperatures shifted to lower temperatures whereas the area of the exotherm decreased quickly as the PC content was increased. The Avrami exponent, n, decreased from 4.32 to 3.61 as the PC content was increased from 0 to 20 wt %, and the growth rate constant, Z(c), decreased gradually as well. This suggests that the nucleation mechanism exhibits the tendency of changing gradually from a thermal nucleation to an athermal mode although the growth mechanism still remains three-dimensional. When epoxy (2.7 phr) was added as a compatibilizer during melt blending, the T-ci and Tc shifted slightly to higher temperature (<= 2 degrees C), and the crystallization enthalpy, however, exhibited an increased crystallinity with the exception of the 90/10/2.7phr PTT/ PC/Epoxy. This suggests that the epoxy make a positive contribution to the PTT crystallization. Moreover, the influences of epoxy on the crystallization behaviors of PTT/ PC blends are related to the epoxy content. By contrast, the compatibilizer of ethylene-propylene-diene copolymer graft glycidyl methacrylate (EPDM-g-GMA, <= 6.3 phr) had little effect on the crystallization behavior of PTT/PC blends. For PTT/PC/Epoxy (2.7phr) blends, the Avrami exponent, n, decreased to near 3, while the growth rate constant, Z(c), increased slightly as PC content was increased from 0 to 20 wt %. It is suggested that epoxy accelerated the process of the nucleation mechanism changing from thermal nucleation to an. athermal mode. The EPDM-g-GMA had little effect on the nucleation mode and spherical growth mechanism. The PTT spherulite morphologies in PTT/PC blends were very sensitive to blend composition. Completely different morphologies were observed in pure PTT, PTT/PC, PTT/PC/Epoxy, and PTT/PC/EPDM-g-GMA blends.