CRYSTALLIZATION OF POLY(ETHYLENE-TEREPHTHALATE) POLYCARBONATE BLENDS .2. THE EFFECTS OF FIBER REINFORCEMENT

The effect of fiber reinforcement on the crystallization of poly(ethyl ene terephthalate) (PET) in blends of PET and polycarbonate (PC) is de termined using differential scanning calorimetry (DSC). Isothermal cry stallization rate of PET in PET/PC blends (80% and 60% PET by weight) is depressed as a result of Kevlar 49 and glass fiber reinforcement. I n contrast, the crystallization rate of the same PET (no PC present) i s enhanced by the Kevlar. The degree of crystallinity and melting temp erature of PET in fiber-reinforced PET/PC is also depressed relative t o that of unreinforced PET/PC and fiber-reinforced PET. These results show that there is a significant interaction between the effects of fi ber reinforcement and of the PC component on the crystallization of PE T in PET/PC composites. The PET/PC blends studied display two glass tr ansition temperatures, characteristic of an immiscible blend. When gla ss fibers are used as the reinforcing phase, the T-g of PET is depress ed. Optical microscopy observations are also consistent with an immisc ible blend. When Kevlar fibers lie in a crystallizable (PET) domain, c rystallites are densely nucleated on the fiber surface to induce trans crystallinity. Glass fibers produce less densely nucleated surface cry stals in these systems. (C) 1996 John Wiley & Sons, Inc.