PP/LCP composites: effects of shear flow, extensional flow and nanofillers

PP/LCP composites moulded under shear flow and extensional flows were prepared in this work. It was observed that the predominating shear flow during injection moulding was unable to induce in-situ reinforcements in the Rodrun LC5000/PP blend. With the introduction of an additional drawing process, fibrous LCP was developed. The fibrillation of the LCP phase was found to increase with the draw speed and the formation of LCP fibrils was manifested as higher strength and stiffness. However, due to the poor adhesion between the pre-generated LCP fibrils and PP matrix, the strength of the extensional PP/LCP composites was lower than that of direct injection moulded LCP/PP blend. In another approach, silica fillers were introduced to the LCP/PP blend and the LCP fibrillation was found to improve. The nanosilica was believed to behave as a viscosity thickening agent and was able to promote the LCP droplet-fibril transition effectively. The nanofiller/LCP/thermoplastic system possessed dual reinforcements which imparted good properties to the composite.