ELECTRIC MODULUS AND INTERFACIAL POLARIZATION IN COMPOSITE POLYMERIC SYSTEMS

The applicability of the electric modulus formalism is investigated on a Debye-type relaxation process, the interfacial polarization or Maxw ell-Wagner-Sillars effect. Electric modulus, which has been proposed f or the description of systems with ionic conductivity and related rela xation processes, presents advantages in comparison to the classical a pproach of the real and imaginary part of dielectric permittivity. In composite polymeric materials, relaxation phenomena in the low-frequen cy region are attributed to the heterogeneity of the systems. For the investigation of these processes through electric modulus formalism, h ybrid composite systems consisting of epoxy resin-metal powder-aramid fibres were prepared with various filler contents and their dielectric spectra were recorded in the frequency range 10 Hz-10 MHz in the temp erature interval 30-150 degrees C. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami equations of dielectric relaxation are expressed in the electric modulus form. Correlation between experimental data a nd the various expressions produced, shows that interfacial polarizati on in the systems examined is, mostly, better described by the Davidso n-Cole approach and only in the system with the higher heterogeneity m ust the Havriliak-Negami approach be used. (C) 1998 Chapman and Hall.