Viscosity changes due to TLCP melt structure development in very low concentration TLCP/HMMPE blends

A low nematic transition temperature thermotropic liquid crystalline polymer (TLCP), copolyester of HBA/HQ/SA, acts as a processing aid for high molecular mass high density polyethylene (HMMPE). Even at TLCP concentrations of 0.2, 0.5 and 2 wt%, there is a bulk viscosity reduction >90% at 185 degrees C. The processing window is expanded from a shear rate of 100 s(-1) to > 1000 s(-1). Rheo-optical studies show the melt structure is an important factor in reducing viscosity: biphasic, anisotropic TLCP being best. The mechanism is believed to be the forced alignment of HMMPE molecules in the presence of highly oriented TLCP molecules