Dielectric properties and thermal conductivity of graphene nanoplatelet filled poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend

Poly(methyl methacrylate) (PMMA) and graphene nanoplatelet (GNP) was introduced into poly(vinylidene fluoride) (PVDF) via a solution blending process, and a series of PVDF/PMMA/GNP composites were obtained. Scanning electron microscope (SEM) micrographs of the composite with 4 wt% GNP loading showed that GNP randomly dispersed and partly arranged parallel to each other in the matrix. Fourier transform infrared (FT-IR) spectroscopy results and X-ray diffraction (XRD) analysis revealed the increasing percentage of β- and γ-phase PVDF crystals in the composites with increasing the GNP contents. The frequency dependent electrical conductivity and dielectric properties of composites have been performed in the range of 10² − 10⁷ Hz which obeyed the percolation theory. Dielectric constant and dielectric loss of composites increased with increasing GNP contents in the all frequency region. A dielectric constant of ~148 and dielectric loss of ~0.3 was observed at 10² Hz with 4 wt% of GNP loading, which is near the percolation threshold. Meanwhile, the thermal conductivity reached up to 0.84 W/m K for PVDF/PMMA/GNP composites with 4 wt% of GNP loading. An approch was provided to develop a variety of highly thermally conductive dielectric materials.