Enhanced electrical conductivity and EMI shielding performance through cell size-induced CNS alignment in PP/CNS foam

The incorporation of cell structure within conductive polymer composites (CPCs) presents significant advantages for electrical properties. An innovative approach, involving the enlargement of cell size, was proposed to enhance electrical conductivity (EC) and electromagnetic interference shielding effectiveness (EMI SE). Herein, polypropylene/carbon nanostructure (PP/CNS) nanocomposite foams with a fixed void fraction were produced using core-back foaming injection molding technique, and their cell sizes were well-controlled by modifying the nitrogen (N₂) content. The results reveal that as the cell size increased from 71 to 317 μm, the EC and EMI SE increased from 1.43 × 10⁻³ to 5.07 × 10⁻³ S/cm and from 48.5 to 59.2 dB, respectively. The enhanced EC was attributed to the slightly aligned CNS and the shorter actual conductive paths. Furthermore, our novel CPC foams showed a maximum specific SE of 329 dB∙cm²/g, exhibiting superior EMI shielding performance compared to other existing CPC foams.