Interrelationships between Rheological, Morphological, and Mechanical Properties of Polystyrene/Liquid Crystalline Polymer Blends

Abstract

The effects of the viscosity ratio of dispersed phase to matrix on the rheological, morphological, and mechanical properties of blends of polystyrene and two rheologically different liquid crystalline polymers (LCPs) were investigated. Two different rheological behaviors are obtained by blending polystyrene (PS) and two different LCPs: one is the case that the viscosity of dispersed phase is lower than that of matrix phase as observed in PS/Rodrun blends, and another one is the case that the viscosity of dispersed phase is higher than that of matrix phase as observed in PS/Vectra blends. Scanning electron micrographs of fracture surfaces of injection-molded samples show that the finely distributed LCP fibril structure is observed for PS/Rodrun blends where the viscosity of the dispersed LCP phase is lower than that of the polystyrene matrix phase, whereas dispersed LCP phase in PS/Vectra blends show the spherical form of LCP domains. Mechanical properties of injection molded specimens show that the modulus of PS/Rodrun blends shows a strong positive deviation from the simple additive rule, whereas the modulus of PS/Vectra blends follows the simple additive rule of mixture. These mechanical properties are well consistent with the morphological characteristics of the PS/LCP blends.