Strong and high void fraction PP/CNS nanocomposite foams fabricated by core-back foam injection molding

Polypropylene/carbon nanostructure (PP/CNS) nanocomposite foams with a void fraction as high as 78% were successfully prepared by foam injection molding (FIM) with core-back operation. Rheological curves and differential scanning calorimetry results showed that the added CNS significantly improved the melt strength and accelerated the crystallization process of PP, respectively. A high mold temperature was applied to overcome the adverse effect of CNS, which had a high thermal conductivity and went against the preparation of high void fraction (VF) products. Thus, adding CNS could dramatically increase cell density by three orders of magnitude. With a CNS loading of 5 wt%, the PP/CNS nanocomposite foam with a cell size of about 60 mu m, cell density over 10(7) cells/cm(3), and a void fraction of 78% was obtained. More interestingly, the specific flexural modulus of the PP/CNS composite foam with 50% void-fraction was increased by 37% relative to the neat solid injection-molded PP. PP/CNS composite foams with adjustable cell structure and good mechanical properties show great potential for electromagnetic interference (EMI) shielding and sensors applications.

Automated summary

Polypropylene/carbon nanostructure (PP/CNS) nanocomposite foams with high void fraction and good mechanical properties were successfully prepared using foam injection molding technique. The addition of carbon nanostructures improved the melt strength and crystallization process of PP, and a high mold temperature overcame the adverse effect of CNS, leading to significantly increased cell density.