THERMAL-CONDUCTIVITY AND THERMAL EXPANSIVITY OF IN-SITU COMPOSITES OFA LIQUID-CRYSTALLINE POLYMER AND POLYCARBONATE

The thermal conductivity and thermal expansivity of extruded blends of a liquid crystalline polymer (LCP) and polycarbonate (PC) with volume fraction (V-f) of LCP between 0.09 and 0.8 have been measured as func tions of draw ratios lambda ranging from 1.3 to 15. At V-f < 0.3, the LCP domains are dispersed in a PC matrix and the aspect ratio of the d omains increases with increasing lambda. At V-f > 0.55, phase inversio n has occurred and the LCP becomes the continuous phase. The axial the rmal conductivity K-parallel to increases while the axial expansivity alpha(parallel to) decreases sharply with increasing lambda, as a resu lt of the higher aspect ratio of the LCP fibrils and the improved mole cular orientation within the fibrils. Since the transverse thermal con ductivity and expansivity are little affected by drawing, the blends e xhibit strong anisotropy in the thermal conduction and expansion behav ior at high lambda. At V-f < 0.3, the behavior of K-parallel to is rea sonably modeled by the Halpin-Tsai equation for short fiber composites . At high draw ratio (lambda = 15), all the blends behave like unidire ctional continuous fiber composites, so K-parallel to and alpha(parall el to) follow the rule of mixtures and the Schapery equation, respecti vely.