Microcellular Conductive Carbon Black or Graphene/PVDF Composite Foam with 3D Conductive Channel: A Promising Lightweight, Heat‐Insulating, and EMI‐Shielding Material

In this study, a lightweight microcellular carbon‐based filler/poly(vinylidene fluoride) (PVDF) composite foam is fabricated with a 3D conductive network that is thermally insulating, electrically conductive, and fabricated on a large scale. This composite can be used for high‐efficiency thermal insulation and electromagnetic interference (EMI) shielding applications. The prepared composite demonstrates low density, high electrical conductivity, and excellent thermal insulation properties. The structure and density of the conductive network and the carbon‐based filler content has a significant influence on the electrical conductivity of the prepared composite foam. Although the composite comprises microcellular PVDF beads of the same density, the conductivity of the composite‐comprising strip beads is greater than that comprising spherical beads. In the same conductive network structure, as the size of the microcellular PVDF beads decrease, the conductive network becomes denser, which results in a higher conductivity. Furthermore, with an increase in the conductive filler content, the conductivity improves significantly. Excellent EMI shielding materials with optimal filler content and particle shapes, exhibiting EMI shielding effectiveness of up to 40–50 dB, are developed. The prepared composite foam possesses excellent application potential in the fields of ultra‐light thermal insulation, conductivity, and EMI shielding. The ultra‐lightweight (density,