Flexural properties and morphology of microcellular-insert injection molded all-polypropylene composite foams

Single-polymer composite foams or all-polymer composite foams have been developed with further reduced weight, good interfacial adhesion and enhanced recyclability. All-polypropylene (PP) composite foams were prepared by the insert injection molding combined with microcellular injection molding. Flexural properties of the all-PP composite foams were reported and compared with solid PP, all-PP composites and PP foams. In comparison with solid PP, the 4.23% weight reduction, 16.52% increase of flexural strength and 20% increase of flexural modulus were achieved by the all-PP composite foams produced at the injection temperature of 220 °C and injection speed of 40 mm/s. Especially, the all-PP composite foams could have lower weight but higher flexural strength than the all-PP composites without foaming. The effect of injection temperature and injection speed on the flexural properties of all-PP composite foams was investigated to explore the optimum processing parameters for balancing good interfacial adhesion and weight reduction. Morphology properties were also investigated. The effect of processing conditions on the cell size and cell density of the all-PP composite foams was analyzed.