Poly(Vinylidene Fluoride-Hexafluoropropylene) Composites With Carbon Based Nanofillers for Electromagnetic Interference Shielding

In the current work, a series of flexible polymer matrix composites (PMCs) based on poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) as the polymer matrix and carbon nanofillers, namely single-walled nanotubes (SWCNT) or carbon blacks (CB), were fabricated via a facile preparation method of blending and solution casting. The electrical conductivity, morphology, dielectric constant, mechanics, and electromagnetic interference (EMI) shielding properties of the composite films were adjusted by varying the carbon type (CB = Ketjenblack, Vulcan, or SWCNT = Tuball) and amount (0.1-15 wt%). The influence of the conductive nanofillers on the EMI shielding effectiveness (SE) and microwave absorbing properties in the X-band frequency range (8-12 GHz) were investigated. By increasing the carbon content, the EMI shielding properties of the composite films were improved due to an increase in the magnitude of the electromagnetic properties. As the loading of these carbon fillers approach the percolation threshold, the dielectric constant of the composite can dramatically increase because of the construction of a microcapacitor network. However, these nanofillers/polymer composites generally have high dielectric loss near the percolation threshold due to the direct connection between carbon nanofillers. The PVDF-HFP/Tuball composite particularly contributed low dielectric loss to the electromagnetic (EM) wave, resulting in excellent microwave absorption properties with a SE per unit thickness of 337.5 dB/mm and 2.5x less weight compared with conventional aluminum with the same SE, demonstrating the promise of using these materials as practical EMI shields.