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

Abstract

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 μm, 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.

Recent Trends in Polymeric Foams and Porous Structures for Electromagnetic Interference Shielding Applications

“…Consequently, the EMI SE produced comparatively higher results than the un-foamed composite counterpart (around 37 dB, almost 30% higher than the non-foamed composite). A similar injection molding-based foaming process (specifically, the core-back injection process) was used by Wang and co-workers [ 12 ] to prepare lightweight polypropylene (PP)-carbon nanosheets (CNS) and nanocomposite foams with microcellular structures. In this work, the authors showed that it was possible to obtain foams with higher specific flexural modulus values than that of their respective un-foamed injection-molded counterparts; hence, foams show great potential as EMI shields for sensor-based applications.…”

Recent Trends on Polymeric Foams and Porous Structures for Emi Shielding Applications

“…As mentioned before, as the combination of CF addition and chemical foaming led to foams with more uniform smaller-sized cellular structures, EMI SE resulted comparatively higher than the unfoamed composite counterpart (almost 37 dB, almost 30% higher than the non-foamed composite). A similar injection molding-based foaming process, more specifically core-back injection, was used by Wang and co-workers [28] to prepare lightweight polypropylene (PP)-carbon nanosheets (CNS) nanocomposite foams having a microcellular structure. In this work, the authors showed that it was possible to obtain foams having higher specific flexural modulus values than that of their respective unfoamed injection-molded counterparts, hence foams showing great potential as EMI shields for sensor applications.…”