A comprehensive investigation of dielectric properties of epoxy composites containing conducting fillers: Fluffy carbon black and various types of reduced graphene oxide

Abstract The dielectric properties of epoxy nanocomposites with conducting nanofillers, such as graphene based and fluffy carbon black (FCB) were investigated in the frequency range of 40 to 30 MHz using an impedance analyzer to measure the dielectric permittivity, tan δ and AC conductivity. At very low filler loadings, epoxy nanocomposites showed remarkable dielectric characteristics. Dielectric constant of the composites decreased with increasing frequency and increased with filler loading. This is related to a decrease in interfacial polarization with increasing frequency and greater interfacial polarization with increase in filler loading. Dielectric loss peaks of epoxy nanocomposites with frequency suggested that both DC conductivity and dielectric polarization processes due to inhomogeneity within the nanocomposites contribute towards dielectric loss. Rising of AC conductivity of the composites with frequency was mainly due to hopping of charge carriers. An AC conductivity of 8.33 × 10 −4  S/m and 2.455 × 10 −5  S/m at 30 MHz was recorded for FCB/epoxy at 5 phr composite and neat epoxy. This composite also exhibited the maximum dielectric permittivity, 3.16 at 40 Hz and 0.82 at 30 MHz. The distinctive dielectric properties of epoxy‐based nano dielectric systems are due to the significant volume fraction of interfaces in the bulk of the material and the consequent interactions between charged nanoparticle surface and epoxy chains.