Modification of the processing window of a thermotropic liquid crystallinepolymer by blending with another thermotropic liquid crystalline polymer

This paper is concerned with properties and processing performance of two t hermotropic liquid crystalline polymers (TLCPs) produced by DuPont (HX6000 and HX8000) with widely varying melting points and blends of these two TLCP s. This work was carried out in an effort to develop a TLCP suitable for ge nerating poly(ethylene terephthalate) (PET) composites in which the melting point of the TLCP was higher than the processing temperature of PET. Stran ds of the neat TLCPs and a 50/50 wt % TLCP-TLCP blend were spun and tested for their tensile properties. It was determined that the moduli of the HX80 00, HX6000, and HX6000-HX8000 blend strands were 47.1, 70, and 38.5 GPa, re spectfully. Monofilaments of PET-HX6000-HX8000 (50/ 25/25 wt %) were spun w ith the use of a novel dual extruder process. The strands had moduli as hig h as 28 GPa, exceeding predictions made using the rule of mixtures and tens ile strengths around 275 MPa. The strands were then uniaxially compression molded at 270 degrees C. It was found that after compression molding, the m odulus dropped from 28 GPa to roughly 12 GPa due to the loss of molecular o rientation in the TLCP phase. However, this represents an improvement over the use of HX8000. (C) 1999 John Wiley & Sons, Inc.