High dielectric permittivity and low percolation threshold in nanocomposites based on poly(vinylidene fluoride) and exfoliated graphite nanoplates

A nanocomposite system consisting of poly(vinylidene fluoride) and exfoliated graphite nanoplates (PVDF/xGnPs) was proposed. The xGnPs were selected as the conductive filler, because of their good electrical and thermal conductivity, high mechanical strength, and large aspect ratio. A required amount of xGnPs was first ultrasonically dispersed in 200 mL of N,N-dimethylformamide (DMF) for 1 hour. Then, PVDF was added into the xGnP suspension, and the mixture was poured onto a glass plate to form a thin film after stirring for 30 mm at 80°C, and ultrasonicating for another 2 h, and dried at 70°C for 3 days. Samples for testing were made by hot pressing several solution cast films stacked together at 200°C. The dielectric properties of the samples, when measured, showed a significant increment because of the inhomogeneous dispersion of xGnPs in the PVDF polymer matrix.