Morphology in Blends of a Thermotropic Liquid Crystalline Polymer and Polypropylene

Abstract

Abstract By monitoring the development of morphology a novel dual extrusion process from the point that the thermotropic liquid crystalline polymer (TLCP) stream meets the matrix material to the final drawn strand, a clear mechanism for the development of the TLCP reinforcement is presented. It was found that under appropriate mixing configurations the fibrillar TLCP morphology seen in strands produced from this method originate at the onset of mixing in the phase distribution system and are subsequently refined as the melt passes through the static mixing elements. The axially continuous morphology seen at the entrance of the die is maintained and further developed as the blend passes through the die and is drawn. In contrast, strands produced using the single extruder blending or the dual extrusion method with excessive mixing produce a droplet morphology prior to the die. At a very low concentration of TLCP, the droplets are too small and well dispersed to sufficiently coalesce and deform into fibrils in the elongational flow field of the die and drawing process. These phenomena result in an undesirable morphology for self reinforcement which clearly has been seen in the measured mechanical properties of the strands.