Dielectric relaxation behavior of exfoliated graphite nanoplatelets filled ethylene vinyl acetate copolymer and ethylene propylene diene terpolymer blend

Exfoliated graphite nanoplatelets(xGnP) filled 50:50 blend of ethylene vinyl acetate copolymer(EVA) and ethylene propylene diene terpolymer (EPDM) composites were prepared by solution casting followed by compression moulding method. The microstructure, dielectric characteristics and conducting behaviour were investigated as function of xGnP loading and frequency range of 10² to 5 × 10⁶Hz. Dielectric constant increases with increase in xGnP loading and showed maximum value at 10 phr loading and then decreases with increase in xGnP loading. The enhancement of dielectric constant is due to Maxwell–Wagner–Sillars (MWS) interfacial polarization between the exfoliated graphite nanoplatelets and EVA/EPDM polymer blend interfaces. From Nyquist plot it is observed that with increase in xGnP loading beyond 6 wt% semicircles are obtained which become prominent above 8 wt% loading. AC conductivity values increases with increase in xGnP loading and a percolation threshold of 6 wt% was observed for EVA-EPDM (50:50) blend system which is much lower than the EVA-xGnP as well as EPDM-xGnP systems. The non-linear current–voltage(I–V) characteristics below the percolation threshold is obtained which is due to tunnelling and at higher xGnP loading, a liner I–V characteristic is due to direct contact between the xGnP nanoplatelets.