Dielectric analysis of high-density polyethylene-graphite composites for capacitor and EMI shielding application

In this article, we present and analyze the dielectric properties of high-density polyethylene (HDPE)-graphite(Gr) composites in low and radio frequency ranges for capacitor and electromagnetic interference (EMI) shielding application, respectively. The HDPE-Gr composites were prepared by mixing and the hot compression mold technique. The dielectric constant and AC conductivity of HDPE-Gr composites according to graphite volume fraction follow the power law model of percolation theory. The percolation threshold of the composites was estimated to be 0.039 (similar to 7 wt % of Gr). The HDPE-Gr composites exhibited high dielectric constants, high dissipation factors, and high AC conductivities at a certain addition of graphite in low frequency and radio frequency regions. The AC conductivity of the composites with the higher content of graphite depicted frequency independency in low and radio frequency region. The EMI shielding properties of the HDPE-Gr composites was evaluated in the radio frequency region and it was found that the maximum EMI shielding of the composites was obtained. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012