EFFECTS OF PROCESSING CONDITIONS ON THE MECHANICAL PERFORMANCE OF MALEIC-ANHYDRIDE COMPATIBILIZED IN-SITU COMPOSITES OF POLYPROPYLENE WITH LIQUID-CRYSTALLINE POLYMER

Maleic anhydride compatibilized blends of isotactic polypropylene (PP) and thermotropic liquid crystaline polymer (LCP) were prepared either by the direct injection molding (one-step process), or by twin-screw extrusion blending, after which specimens were injection molded (two-s tep process). The morphology and mechanical properties of these inject ion molded in situ LCP composites were studied by means of scanning el ectron microscopy (SEM), Izod impact testing, static tensile, and dyna mic mechanical measurements. SEM observations showed that fine and elo ngated LCP fibrils are formed in the maleic anhydride compatibilized i n situ composites fabricated by means of the one-step process. The ten sile strength and modulus of these composites were considerably close to those predicted from the rule of mixtures. Furthermore, the impact behavior of LCP fibril reinforced composites was similar to that of th e glass fiber reinforced polymer composites, On the other hand, the ma leic anhydride compatibilized blends prepared from the two-step proces s showed lower mechanical performance, which was attributed to the poo rer processing behavior leading to the degradation of PP. The effects of the processing steps, temperatures, and compatibilizer addition on the mechanical properties of the PP/LCP blends are discussed.