Rheological and mechanical properties of polycarbonate-liquid-crystalline polymer blends with controlled chemical reactions

Abstract

Chemical reactions can occur during the melt blending of polymers containing an ester group because ester groups are usually unstable at high temperatures; this instability generally deteriorates the mechanical properties of blends. Here, effects of chemical reactions on the rheological and mechanical properties of polycarbonate (PC)/liquid-crystalline polymer (LCP) blends are carefully investigated to determine a method for minimizing such undesirable impacts. For comparison, a physical blend, in which chemical reactions were minimized, was prepared at 300 degreesC in a twin-screw extruder. Both shear viscosity and complex viscosities of reactive blends were lower than those of physical blends, being almost proportional to [(M-w) over bar](3.4) as a result of depolymerization and transesterification. Because of the enhanced miscibility, the tensile modulus of reactive blends increased compared with that of physical blend, according to the increase in the degree of incorporation (DI). It was also possible to increase tensile modulus if triester was added to the reactive blends. (C) 2001 John Wiley & Sons, Inc.