IN-SITU COMPOSITE - PHENOLPHTHALEIN POLYETHERSULFONE-THERMOTROPIC LIQUID-CRYSTALLINE POLYMER BLENDS

Phase behavior, thermal, theological and mechanical properties plus mo rphology have been studied for a binary polymer blend. The blend is ph enolphthalein polyethersulfone (PES-C) with a thermotropic liquid crys talline polymer (LCP), a condensation copolymer of p-hydroxybenzoic ac id with ethylene terephthalate (PHB-PET). It was found that these two polymers form optically isotropic and homogeneous blends by means of a solvent casting method. The homogeneous blends undergo phase separati on during heat treatment. However, melt mixed PES-C/PHB-PET blends wer e heterogeneous based upon DSC and DMA analysis and SEM examination. A ddition of LCP in PES-C resulted in a marked reduction of melt viscosi ty and thus improved processability. Compared to pure PES-C, the charp y impact strength of the blend containing 2.5% LCP increased 2.5 times . Synergistic effects were also observed for the mechanical properties of blends containing < 10% LCP. Particulates, ribbons, and fibrils we re found to be the typical morphological units of PHB-PET in the PES-C matrix, which depended upon the concentration of LCP and the processi ng conditions.