Microinjection molding of polypropylene/graphite composites

A series of polypropylene/graphite (PP/G) composites were prepared via melt blending, followed by compression molding and microinjection molding (µIM) processes. In μIM, a micropart (µ-part) which has a three-step decrease in thickness along the melt flow direction was fabricated. Volume electrical conductivity of subsequent moldings was measured using a two-point method. The preferred alignment of G along the melt flow direction is beneficial to the enhancement of electrical conductivity in this specific direction. In addition, the thermal behavior of PP, PP/G composites and the thick section of corresponding µ-parts was evaluated by differential scanning calorimetry. Results indicated that the addition of G and the thermo-mechanical history that was experienced by the polymer melts influenced the crystallization process of PP.