The morphology of extruded blends containing a thermotropic liquid crystalline polymer

Abstract

Abstract Three different polymer blends consisting of an isotropic matrix and a ther‐motropic liquid crystalline polymer (LCP) as the reinforcement were extruded. Polycarbonate (PC) and polyetherimide (PEI) were the two matrices, and the LCPs used were Vectraw A950 of Hoechst‐Celanese, a copolyester of hydroxybenzoic and 2,6 hydroxynaphthoic acids and an LCP of Granmont Inc., a condensation polymer of terephthalic acid, (l‐phenylethyl)hydroquinone, and phenylhydroqui‐none. These extrudates were characterized by a quantitative morphological technique to determine the percentage of LCP present as fibrils and the average domain diameter. These experimental observations were then coupled with the component Theological behavior and a simple heat transfer analysis to explain the morphology and property differences between the blends. Blends with the Granmont LCP showed no appreciable increase In the quantity of fibrils with draw ratio, for example, whereas the amount of fibrils in Vectra® blends tended to increase to a plateau with draw. The tensile modulus of the blends agreed well with composite theory, with average fibril moduli of 24.6 GPa and 23,3 GPa for Vectra® and the Granmont LCP, respectively. These differences can be explained in terms of the cooling behavior of the LCPs.