Inhibited transesterification and enhanced fibrillation of TLCP by nano-SiO 2 in polycarbonate matrix

Abstract

Hybrid composites composed of a thermotropic liquid crystalline polymer (TLCP), nano-SiO 2 and polycarbonate (PC) were prepared by melt blending in a twin-screw extruder. Infrared spectroscopy analysis indicated that the transesterification between PC and TLCP molecules during melt blending was significantly reduced in TLCP/PC blends filled with nano-SiO 2, compared to the unfilled TLCP/PC one. Scanning electron microscopy (SEM) observation showed that better compatibility and finer TLCP dispersion were reached in the unfilled blend, which made the fibrillation of TLCP difficult in capillary flow even at high shear rate. In contrast to this, well-developed TLCP fibrils were formed by capillary flow in nano-SiO 2 filled TLCP/PC blends. By increasing the nano-SiO 2 concentration and shear rate, the fibrillation of TLCP was significantly enhanced. Thermodynamically the interfacial tension between these components and dynamically the viscosity ratio of TLCP to PC were used to investigate the mechanism of nano-SiO 2 in inhibiting the transesterification and enhancing the fibrillation of TLCP droplets in these hybrid composites.