A STUDY ON BLENDS OF LIQUID-CRYSTALLINE COPOLYESTERS WITH POLYCARBONATE .2. TRANSESTERIFICATION CONTROL

The inhibited and catalyzed ester exchange (transesterification) durin g melt blending of poly(bisphenol-A carbonate) (PC) and liquid crystal line poly(oxybenzoate-co-ethylene terephthalate) (POB-PET 40/60; P46) was investigated with differential scanning calorimetry. It was found that the ester exchange between P46 and PC was effectively inhibited f or a 20% P46 blend at 240 degrees C, as further confirmed by nuclear m agnetic spectroscopy. When the blending temperature and P46 concentrat ion increased, only the transesterification between the PET segment in P46 and PC took place under inhibition. The morphology of the blends was analyzed with scanning electron microscopy and displayed a disconn ected interface between P46 and PC under inhibition. Conversely, the t ransesterification took place between the POB segment in P46 and PC wh en a catalyst was added. (C) 1996 John Wiley & Sons, Inc.