IN-SITU COMPATIBILITY OF POLYSTYRENE AND LIQUID-CRYSTALLINE POLYMER BLENDS

The styrene-glycidyl methacrylate (SG) copolymer can be used to compat ibilize the immiscible and incompatible blends between polystyrene (PS ) and liquid crystalline polymer (LCP) copolyester. The epoxy function al groups present in the SG copolymer can react with the carboxylic an d/or the hydroxyl terminal groups of the LCP at interface to form the SG-g-LCP copolymer during melt processing. This in situ-formed graft c opolymer tends to reside along the interface to reduce the interfacial tension in the melt state and to increase the interphase adhesion in the solid state. However, the compatibilized PS/LCP blends reduce the number of LCP fibrils formed and have a tendency to form droplet LCP d omains. The overall mechanical properties, stiffness and toughness of the blends improved after compatibilization, but the extent of the imp rovement is not very significant. It appears that the gain from the ad hesion enhancement is more than offset by the loss due to the reductio n in LCP fibril formation. The ethyl triphenylsphosponium bromide cata lyst can further improve the compatibility of the blends by increasing the rate of the graft reaction. Copyright (C) 1996 Elsevier Science L td.