Rheology and Physical Properties of Polysulfone In-Situ Reinforced with a Thermotropic Liquid-Crystalline Polyester

Abstract

Blending Amoco polysulfone Udel P-1700 and Hoechst Celanese thermotropic liquid-crystalline polymer (TLCP) Vectra A-950 in a twin-screw extruder produced in-situ composites. An inclusion of TLCP did not notably change the thermal properties of polysulfone but the rheological properties were notably changed depending on the measured temperature and blend composition. In the vicinity of crystal-nematic transition temperature, an incorporation of TLCP into polysulfone increased the melt viscosity and gave rise to a large yield stress. Above the crystal-nematic transition temperature, however, TLCP dramatically decreased the melt viscosity and the resultant yield stress was very small. The tensile strength and modulus of as-spun polysulfone/TLCP fibers were increased as the TLCP content and spin draw ratio were increased. The increase in tensile strength with spin draw ratio was more noticed with the polysulfone/TLCP fiber containing higher TLCP content. Wide angle X-ray diffraction patterns suggested that the increase in tensile strength is ascribable to the enhanced molecular orientation and resultant fibrillation of TLCP. The compositional moduli of as-spun blend fibers where well fitted to the additivity rule of mixtures, viz., the Tsai-Halpin equation for the reinforcement of infinite aspect ratio.