Morphology and mechanical properties of thermoplastic composites containing a liquid crystalline polymer

Abstract

Morphological and mechanical properties of compression molded composites of a liquid crystalline copolymer (LCP) poly(terephthaloyl chloride)-co-(p,p'-dihydroxydiphenyl sulfone) with polycarbonate (PC), polystyrene (PS) and sulfonated (at a degree of 11%) polystyrene (SPS) are presented and discussed. For LCP/PS and LCP/SPS systems, a sharp two phase morphology was formed which suggested poor interfacial adhesion. However, while a composite plate of 25% LCP/PS could not be fabricated, it was possible for the case of LCP/SPS, indicating some improvement in interfacial bonding by sulfonation. On the other hand, tensile strength of both systems decreased with LCP addition, indicating that 11% sulfonation is not sufficient to introduce significant compatibility, but it was not as dramatic as that for LCP/PS. The performance of the LCP/SPS system was not affected significantly by heat treatment at the process temperature. The LCP/PC system also revealed a two phase morphology, however the interfaces between the LCP domains and the PC matrix were not so well defined showing better interfacial adhesion than the two previous systems studied. Stronger bonding between the LCP and PC resulted in an appreciable improvement in the mechanical behavior of PC by LCP addition. Increasing the processing temperature from 225°C to 245°C appeared to improve the interfacial adhesion, but also resulted in degradation ofPC.