EXTRUSION BLOW MOLDING OF MICROCOMPOSITES BASED ON THERMOTROPIC LIQUID-CRYSTALLINE POLYMERS AND POLYPROPYLENE

This work is concerned with the extrusion blow molding of bottles from pellets of polypropylene (PP) containing pregenerated microfibrils of thermotropic liquid crystal polymers (TLCPs), referred to as microcom posites. The TLCPs used are HX6000 and Vectra A950. The microcomposite s are produced by drawing strands of PP and TLCPs generated by means o f a novel mixing technique and pelletizing the strands. The work was u ndertaken in an effort to improve on the properties observed for in si tu composites in which the TLCP fibrils are generated in elongational flow fields that occur in polymer processing operations and to determi ne if TLCP reinforced bottles could be produced by extrusion blow mold ing of microcomposites. In situ composites usually exhibit highly anis otropic mechanical properties and the properties do not reflect the fu ll reinforcing potential of the TLCP fibers. Factors considered includ e the effect of TLCP concentration and in situ composite strand proper ties on the mechanical properties and anisotropy of bottles made from microcomposites. Specifically, strands having three different draw rat ios are used to produce bottles at 10 and 20 wt% TLCP. Increasing the in situ composite strand modulus is shown to cause an increase in both the machine and transverse direction moduli of the composite bottles. The mechanical properties of the bottles increase with increasing TLC P composition. Finally, the machine and transverse direction propertie s are not balanced in the composite bottles produced in this study (de grees of anisotropy ranging from 1.5 to 1.8). The mechanical anisotrop y is probably the result of a low blow up ratio (2) in the bottles and the TLCP fibers being oriented primarily in the machine direction due to the shear flow in the die.