INSITU COMPOSITE FIBERS - BLENDS OF LIQUID-CRYSTALLINE POLYMER AND POLY(ETHYLENE-TEREPHTHALATE)

To augment the concept of in situ composites as alternatives to fiber-reinforced composites, polyblends of a thermotropic liquid crystalline polymer (LCP) and poly(ethylene terephthalate) (PET) were prepared. Fiber-spinning of the blends was performed on a piston-driven plastometer. Blends of LCP and a low-intrinsic-viscosity PET resin showed poor mechanical performance, which was attributed to their processing behavior. Blends of LCP and a high intrinsic-viscosity PET manifested an almost additive behavior with regard to tensile modulus and strength. Elongation of the blends, however, displayed a radical decline, which is reminiscent of fiber-reinforced composites. Heat treatment of the blend fibers modestly increased the tensile properties of the LCP-rich compositions. Blend fibers from PET-rich compositions exhibit a moderate decline in tensile properties owing to thermal relaxation of PET. The data demonstrate that in situ composites or blends of thermotropic LCPs and isotropic polymers present challenging alternatives to fiber-reinforced composite systems because of their ease of processing.