Microstructural and mechanical characteristics of compatibilized polypropylene hybrid composites containing potassium titanate whisker and liquid crystalline copolyester

Maleic anhydride (MA) compatibilized polypropylene (MPP) hybrid composites reinforced with potassium titanate whiskers (K2Ti6O13) and liquid crystalline polymer (LCP) were prepared in a twin-screw extruder followed by injection molding. The surface of whiskers were treated with tetrabutyl orthotitanate before blending. Scanning electron microscopic (SEM) examination showed that elongated LCP fibrils are formed in the skin section of hybrids reinforced with whiskers of various concentrations. Consequently, the hybrids reinforced with both LCP fibrils and whiskers exhibited anisotropic mechanical properties. Tensile test showed that longitudinal Young's modulus and tensile strength of hybrids tend to increase with increasing whisker content. Moreover, the stiffness and tensile strength of hybrids were higher than those of MPP/K2Ti6O13 composites. Such enhancement in mechanical properties resulted from the compatibilizing effect of MA-grafted-PP, and from the hybrid reinforcing effect of LCP fibrils and K2Ti6O13 whiskers. Torque measurements revealed that LCP addition is beneficial in reducing the melt viscosity of MPP/K2Ti6O13/LCP hybrids. The results of SEM observations generally correlate well with the mechanical measurements. The effects of MA compatibilization on the microstructure and mechanical properties of hybrids are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.