Melt-spinning of in-situ composites of a thermotropic liquid crystalline polyester in a miscible matrix of poly(ether ether ketone) and poly(ether imide)

Blends of a thermotropic liquid crystalline polyester (TLCP) and a thermoplastic matrix of 75 wt% poly(ether ether ketone) and 25 wt% poly(ether imide) were melt-spun into fibers. The fibers were evaluated in terms of morphology and mechanical properties. Composite fibers containing more than 25 wt% TLCP exhibited a morphology in which the TLCP was dispersed as very long fibrils with good alignment of the molecules in the spinning direction; correspondingly the fibers followed the rule of mixtures behavior for stiffness versus composition. For fibers containing 5 and 10 wt% TLCP, both fibril aspect ratio and molecular orientation were lower, and the stiffness was below the rule of mixtures. This difference can be explained by interfacial tension effects, which are of paramount importance in the deformation of TLCP particles into fibrils.