THERMAL AND MECHANICAL-PROPERTIES OF INJECTION-MOLDED LIQUID-CRYSTALLINE POLYMER AMORPHOUS POLYMER BLENDS

Injection molded samples of binary blends of Vectra (LCP) and the thre e amorphous polymers polyethersulfone (PES), polycarbonate (PC), and a romatic poly(ester carbonate) (APEC) have been subjected to morphologi cal and rheological characterization, and coefficients of linear therm al expansion and Young's moduli have been determined. The Young's modu lus of the PES/LCP blends exhibited a near lower-bound behavior that c ould be predicted by the one-adjustable-parameter equations of Halpin- Tsai (xi = 0. 18) and Takayanaga (b = 0.23), whereas the coefficients of linear thermal expansion followed the Takayanaga equation with a va lue of b = 0.50. The chain orientation of the LCP component was essent ially constant in all PES/LCP blends with a Herman's orientation param eter of 0.39 +/-0.03. Transesterification reactions led to randomizati on of the constituents of the PC/LCP and APEC/LCP blends. The effect w as more pronounced in the PC/LCP blends. The introduction of the LCP i nto the PC/LCP blends led to no reduction in melt viscosity and no sel f-reinforcement. APEC/LCP exhibited self-reinforcement in blends with a content greater than 27 vol% LCP, and especially the blend with 67 v ol% LCP. The self-reinforcement was caused by the presence of an orien ted LCP phase, confirmed by X-ray diffraction, and by improved interfa cial bonding, presumably resulting from the transesterification reacti ons occurring at the phase boundaries.