Compatibilization of Poly(Trimethylene Terephthalate)/Polycarbonate Blends by Epoxy. Part 2. Melting Behavior and Spherulite Morphology

Abstract

The melting behaviors of poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends, compatibilized by epoxy, and PTT spherulite morphology in the blends were investigated. When epoxy was present during blending, the melting behaviors of PTT/PC blends changed substantially; glass transition temperatures (Tg's) and cold crystallization temperature (Tcc's) of the PTT‐rich phase shifted to higher temperatures, while Tm's shifted slightly to lower temperatures, indicating that epoxy suppressed considerably all processes of dynamic movements pertinent to molecular (or segmental) movements. The cold crystallization process responded sensitively to thermal history. Changes of Tcc's with composition suggested that the epoxy's compatibilization effect was pronounced when PTT and PC were in near equal content. Recrystallization or reorganization exotherms appeared before melting for isothermally crystallized PTT/PC and PTT/PC epoxy (E) blends. A wide angle X‐ray diffraction (WAXD) analysis showed that, although the perfection of PTT crystallites was influenced either by PC content and the presence of compatibilizer or by the crystallization temperature and crystallization time, PTT's crystal structure was independent of these variables. The polarized light microscopy (PLM) observations showed that PTT spherulite morphology was very sensitive to blend composition. Epoxy addition interfered severely with the growth of PTT spherulites, causing them to be much less developed. When the spherulites grew under a condition of varied composition, they would exhibit diversified spherulite morphology, though in one spherulite.