Transesterification, morphology and some mechanical properties of thermotropic liquid crystal polymers/polycarbonate blends

Blends of polycarbonate (PC) and thermotropic liquid crystal polymer Vectra-A (VA), with up to 20 wt.% VA were prepared at temperatures up to 320 degrees C. Transesterification (TE) was found to take place notably at the highest blending temperature. At this temperature, it increased linearly with the VA content. TE products, located at PC/VA interfaces led to reductions in the size of dispersed phase droplets, as shown by scanning electron microscopy. The inference of increased compatibility was consistent with improvements in mechanical property parameters of the blends. These also showed that mixing time was a factor in defining interfacial states. Acid-base interaction data gave further evidence of the presence of TE products, notably when blending occurred at 320 degrees C, and suggested that similar to 10 wt.% of VA was needed to saturate interfaces with PC. The absolute values of acid and base interaction constants were found to be very low, confirming earlier evidence that near 320 degrees C dispersion forces are dominant at PV/VA interfaces, contributing to enhanced compatibility in blends prepared at these high temperatures. (C) 2000 Elsevier Science B.V. All rights reserved.