Analysis of the dielectric spectroscopy of an epoxy-ZnO nanocomposite using the universal relaxation law

Abstract

There is currently no unified theory that explains the role of nanofillers in polymeric insulation. Consequently, different methods such as dielectric spectroscopy analysis are used to understand this role. The existence of a strong interaction between nanoparticles and a polymer is widely accepted. However, the interaction between dipoles has been taken into consideration in Jonscher's Universal Relaxation Law (URL) but not in the Debye theory. Hence, the URL was used in this article as a method to analyze the spectra of epoxy-ZnO nanocomposites and to try to determine the nanoeffect mechanism. At 160°C above Tg (116°C), the typical phenomenon of low-frequency dispersion occurs in the epoxy-ZnO nanocomposites, and with filler loading increased up to 5 wt %, the value of n (calculated from the ε ra″ spectrum of the nanocomposites) increases both at high and low frequencies. This result indicates that higher loadings correspond to lower dielectric losses changing per radian. Moreover, the decrease in quasi-direction conduction indicates that the gross dielectric losses of the nanocomposites are also less than pure epoxy resin (EP) at low frequencies. This finding may be attributed to the strong bonding between the nanofillers and the EP, which limits the movement of some macromolecular chains. The URL provides an analytical method for determining the mechanism of the effect of nanofillers on polymers. Copyright © 2012 Wiley Periodicals, Inc.