STUDIES ON BLEND OF LIQUID-CRYSTALLINE AND FLEXIBLE POLYMERS .3. ROLE OF CHAIN EXTENDER IN THE BLENDS OF LIQUID-CRYSTALLINE FLEXIBLE POLYESTERS

A chain extender (CE), which is a bifunctional compound and readily reacts with end groups of two polymer chains, was introduced to the liquid crystalline polyester (LCP)/poly(ethylene terephthalate) (PET) blend system. It is expected to react with carboxyl end groups of LCP and PET and connect these polymer components at their interface. 2,2'-(1,4-Phenylene)bis(2-oxazoline), a chain extender, was synthesized from terephthalonitrile and ethanolamine, and was added to the mixture of LCP and PET in a laboratory kneeder at 280-degrees-C (PPL). The small amount of PPL thus obtained was blended with LCP (LCP/PPL). PPL and LCP/PPL were processed into cast films, and the phase morphology and mechanical properties were examined. The LCP components were found to be liquid crystalline in these blends. SEM observation of the fracture surface revealed that fibrillation of the LCP component tended to be low in PPL and LCP/PPL while pure LCP and LCP blended with PET without addition of CE had a highly fibrillar structure. The films of PPL and LCP/PPL had fairly balanced mechanical properties similar to those of LCP, while pure LCP and the blend without CE showed significant anisotropies.