Injection molding of poly(ethylene terephthalate) reinforced with pregenerated thermotropic liquid crystalline polymer microfibrils

摘要

This work was concerned with the injection molding of polytethylene terephtha- late) (PET) reinforced with pregenerated thermotropic liquid crystalline polymer (TLCP) fibrils, where the TLCP bad a higher melt processing temperature than PET. These composites, referred to as pregenerated microcomposites, were produced using a two step processing scheme. First, a novel dual extrusion process was used to spin strands of PET reinforced with nearly continuous TLCP fibrils. Second, these strands were subsequently chopped into pellets and injection molded below the melt processing temperature of the TLCP but above that of PET. This allowed the high modulus TLCP fibrils generated in the spinning step to be retained in the injection molded samples. TLCP concentration and strand draw ratio were varied in the composne strands to determine how they affected mechanical properties. It was shown that the best properties were obtained using strands containing 50 wt.% TLCP with draw ratios >50, which were diluted to the desired loading level with a low viscosity injection molding grade of PET. Specifically, these composites had tensile moduli as high as 5.7 GPa when reinforced with 30 wt.% HX1000. Also, it was determined that pregenerated microcomposites had smoother surfaces than glass-filled PET.