A Study of the Dielectric Relaxation of Nitrile-Butadiene Rubber, Ethylene-Propylene-Diene Monomer, and...

This study presents an integrated analysis of the dielectric characteristics of nitrile-butadiene rubber (NBR), ethylene-propylene-diene monomer (EPDM), and fluoroelastomer (FKM) polymers. Dispersion spectra were obtained over a wide range of frequencies and temperatures, and, via our self-developed "Dispersion Analysis" program, the obtained dielectric spectra were precisely deconvoluted. Notably, α, α', β, and γ relaxation phenomena, including the DC conduction process, were identified in NBR, whereas three relaxation processes, namely, α, β, and the Maxwell‒Wagner‒Sillars (MWS) process, as well as DC conduction, were observed in EPDM and FKM copolymers. The activation energies (Ea) for secondary relaxation-namely, β, γ, and MWS-and the DC conduction process, which are observed in NBR, EPDM, and FKM, were determined via the Arrhenius temperature dependence model, and these values were compared with previously published results. Furthermore, the glass transition temperature (Tg), extrapolated from the relaxation rate of the α process, was estimated via the Vogel-Fulcher-Tamman-Hesse (VFTH) law. The values of Tg obtained using dielectric spectroscopy for NBR, EPDM, and FKM agreed well with the differential scanning calorimetry (DSC) measurements. This study provides foundational insights into the dielectric properties of widely used rubber polymers, offering a comprehensive reference for future research.