Electromagnetic Interference Shielding Foams Based on Poly(vinylidene fluoride)/Carbon Nanotubes Composite

Polymeric electromagnetic interference (EMI) shielding foaming materials are found and applied in many frontier fields such as aerospace, transportation, and portable electronics. In this paper, a foam based on a composite system of poly(vinylidene fluoride) (PVDF) filled with carbon nanotubes (CNTs) is prepared for EMI shielding properties by using a solid-state supercritical CO₂ foaming strategy. PVDF is chosen as the matrix because of its excellent chemical resistance, thermal stability, and flame retardancy. The inclusion of CNTs renders this composite system enhanced complex viscosity and storage modulus by about two orders of magnitude. The electrical conductivity and EMI specific shielding effectiveness of obtained foams can be adjusted and reached the optimum value of 0.024 S m⁻¹ and 29.1 dB cm³ g⁻¹, respectively, originating from the gradual development of interconnected CNTs and conductive CNTs network as well as the introduction of cell structure in PVDF matrix. Interestingly, the reorientation of CNTs caused by foaming process results in electrical conductivity percolation threshold of PVDF/CNTs foams markedly decreases, in comparison to their unfoamed samples. This study provides a facile, efficient, green, and economic route for the preparation of EMI shielding foams consisted of fluorinated polymers and carbonaceous fillers.