Effects of chemical reactions on the properties of polycarbonate liquid crystalline polymer blends

Abstract

Effects of chemical reactions on the properties of the polycarbonate (PC)/ liquid crystalline polymer (LCP) blends are considered here. Not only thermal and rheological behaviors, but also morphology and molecular weight change are investigated. Reactive blends were prepared in a cylindrical flask at 300 degrees C with varying processing time in the presence of a catalyst by the melt-phase reactions. For comparison, physical blends, in which chemical reactions were minimized, were also prepared at 300 degrees C in a twin-screw extruder. It seems that transesterification and repolymerization did not occur, but depolymerization reaction took place slightly in PC/LCP physical blends. In reactive blends, however, transesterification and repolymerization as well as depolymerization reaction took place simultaneously. The depolymerization reaction occurred mainly at an early stage of processing; whereas, repolymerization reaction becomes especially dominant after some time (more than 30 min) in the presence of the catalyst, which had a great impact on its molecular weight. Also, chemical reactions changed the glass transition temperature and morphology as well as rheological behavior, which resulted in the enhanced miscibility in reactive blends. (C) 1999 John Wiley & Sons, Inc.