Microcellular polypropylene single-polymer composites prepared by insert-microcellular injection molding

An insert-microcellular injection molding process was performed on an injection molding machine equipped with a supercritical fluid system. The prepared microcellular polypropylene (PP) single-polymer composites (SPCs) combine the advantages of SPCs with benefits of microcellular plastics, they hold the promise for further reduced weight, improved fiber-matrix interface and enhanced recyclability. In comparison with the solid PP, the weight reductions of the tensile and impact microcellular PP SPCs (MPPSPCs) could be up to 12.9% and 3.3% respectively, the tensile and impact strengths of the MPPSPCs were improved by 59% and 1799% respectively. Based on the tensile properties, the injection temperature of 220 °C and injection speed of 70 mm/s were the optimum processing for the tensile MPPSPC samples. The typical morphology structure of the MPPSPC sample includes five different layers: sandwiched fabric layer, transition layer between fabric and core, center core layer, transition layer between skin and center core, skin layer.