Incorporating a microcellular structure into PVDF/graphene-nanoplatelet composites to tune their electrical conductivity and electromagnetic interference shielding properties

In this study, we found a simple and effective method to fabricate lightweight poly(vinylidene fluoride) (PVDF)/10 wt% graphene nanoplatelet (GnP) nanocomposite foams with excellent electromagnetic interference (EMI) shielding effectiveness. To this end, solvent blending, film casting, and hot compression procedures were used. The PVDF/10 wt%-GnP nanocomposite foams, which had different microcellular structures, were obtained by adjusting the foaming parameter. Notably, the electrical conductivity and the EMI shielding properties decreased linearly with elevated foaming degree (i.e., the void fraction). Furthermore, they quickly decreased, having a large slope with an increasing void fraction, when the void fraction was below the critical foaming degree of 55% void fraction. When the void fraction was above this critical foaming degree, the electrical conductivity and EMI shielding values decreased slowly with a smaller slope. The EMI shielding properties were critically determined by the foam thickness. The EMI shielding properties of the PVDF/10 wt%-GnP foam with a void fraction of 48.7% increased from 12.4 to 32.2 dB at 26.5 GHz and from 15.2 to 37.4 dB at 40 GHz when the sample thickness increased from 1.5 to 3.0 mm. We concluded that the PVDF/GnP composite foams with tunable electrical conductivity and light weight offered much promise for use as excellent EMI shielding materials. Moreover, this study adopted a novel approach toward the design of conductive lightweight polymer/carbon composite foams for use in a wide range of electronic applications.