Dielectric Relaxation Behavior of Exfoliated Graphite Nanoplatelet-Filled EPDM Vulcanizates BIKASH KUMAR DASH, 2 P. GANGA RAJU ACHARY, 2 NIMAI C. NAYAK, 1,4 and R.N.P. CHOUDHARY 3 1.—Center for Nanoscience and Nanotechnology, Siksha ‘O’ Anusandhan University, Bhuba- neswar, Odisha 751030, India. 2.—Department of Chemistry, Siksha ‘O’ Anusandhan University, Bhubaneswar, Odisha 751030, India. 3.—Advanced Materials Research Laboratory, Department of Physics, Siksha ‘O’ Anusandhan University, Bhubaneswar, Odisha 751030, India. 4.—e-mail: nimainayak@soauniversity.ac.in The present study investigates the dielectric relaxation and mechanical behavior of exfoliated graphite nanoplatelet (XgnP)-filled ethylene-propylene- diene terpolymer (EPDM) vulcanizates with variation in frequency, tempera- ture and xGnP loading. The samples were prepared by a solution–cast method using toluene as the solvent followed by compression molding. The enhanced permittivity and ac conductivity which sharply changes above 20 wt.% of xGnP loading shows the conducting behavior of the composites. The real parts of the impedance for the vulcanizates were continuously decreased up to 40 wt.% whereas the complex part shows an increasing tendency at the same loading expressing the increase in the conductivity of the vulcanizates. The percolation threshold of the xGnP-loaded EPDM vulcanizates was at 25 wt.% of xGnP loading. A more prominent effect of temperature on dielectric loss tangent is observed at 85°C, and 100°C. The ac conductivity increases with the rise in temperature. The Nyquist plots of xGnP-reinforced EPDM show the small intercepts on the Z¢ axis at 85°C, and 100°C for the 40 wt.% loading. The experimental complex impedance plots were in good agreement with the model-fitted plots. The tensile strength of 15 wt.% xGnP-filled vulcanizate increases up to 12 times more than the unfilled EPDM whereas the elongation at break (%) increases up to 700% at the same loading of xGnP. Young’s modulus has been doubled and quadrupled for the vulcanizates with 20 and 40 wt.% of xGnPs, respectively, compared to the pure EPDM samples. The results indicate that the xGnP–EPDM conductive composite can find applica- tions in the area of antistatic material, electrostatic discharge gaskets, etc. Key words: EPDM, xGnP, dielectric, nyquist plot INTRODUCTION Conducting elastomeric composites have been attracting extensive interest due to their wide range of applications such as antistatic materials, spark plug cables, high voltage cable insulation, flexible electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding materials. These con- ducting composites are prepared by incorporating carbonaceous materials like carbon black, 1–5 gra- phite, carbon fibers, 6 carbon nanotubes (CNTs), graphene and exfoliated graphite nanoplatelets (xGnP) 7 into a polymer matrix. Elastomeric matri- ces, like styrene butadiene rubber (SBR), isobuty- lene isoprene rubber (IIR), natural rubber (NR), ethylene propylene rubber (EPR), ethylene vinyl acetate (EVA), nitrile butadiene rubber (NBR), and ethylene-propylene-diene terpolymer (EPDM), are extensively used. EPDM is an elastomeric polymer having super- oxidative stability and excellent weathering (Received September 7, 2015; accepted September 1, 2016) Journal of ELECTRONIC MATERIALS DOI: 10.1007/s11664-016-4935-1 Ó 2016 The Minerals, Metals & Materials Society