Morphological Characteristics and the Modulus of Liquid Crystalline Polymer Fibers Dispersed in a Thermoplastic Matrix

Abstract

The morphology of a polycarbonate (PC)-based blend containing a thermotropic liquid crystalline polymer (LCP) component has been characterized in terms of the layer structure, layer thickness, aspect ratio, and number of the shear-induced fibers developed during injection molding. This dispersed LCP phase was still embedded as fibers and deformed droplets in the PC matrix, and their tensile modulus was usually unknown due to the testing problems. Based on the morphological characteristics, a calculation procedure has been developed to estimate the modulus of these fibers and droplets by using a set of micromechanical models. It has been found that the average tensile modulus of these shear-induced LCP fibers and deformed droplets seems to be a material constant, independent of the injection molding condition, i.e., the shear flow condition. For the LCP Vectra A950 studied, the calculated tensile modulus was 24.0 GPa. This value was in fair agreement with that reported in literature. It was larger than that of the injection-molded pure LCP samples and smaller than that of the drawn pure LCP strand.