THE VISCOSITY REDUCING EFFECTS OF VERY-LOW CONCENTRATIONS OF A THERMOTROPIC COPOLYESTER IN A MATRIX OF HDPE

A thermotropic liquid crystalline polymer (TLCP), denoted as TLCP(1), was used as a processing aid for high density polyethylene (HDPE). The TLCP was a copolyester of hydroxybenzoic acid, hydroquinone and sebac ic acid and was blended with HDPE to give 0.2, 0.5 and 2 wt% TLCP(1) b lends. At a temperature of 185 degrees C, when TLCP(1) is in the nemat ic regime, the processing window for HDPE was increased tenfold from a maximum shear rate of 100 s(-1) for pure HDPE to 1170 s(-1) for a 2 w t% TLCP(1) blend, There were large viscosity reductions of between 85% and 90% compared with the pure HDPE when the blended material was use d at a wall shear stress value of approximately 2.4 x 10(5) Pa. This v iscosity reduction was attributed to the TLCP(I) droplets changing sha pe from spheres to slender fibrils under shear flows.