Abstract
A diglycidylether of bisphenol A (DGEBA) epoxy resin was synthesized, and cured with 3, 3' diaminodiphenyl sulfone (DDS) at a curing temperature of 120 degrees C. The relaxation properties of the realized polymers were studied by two complementary techniques: dielectric relaxation spectroscopy (DRS), in the temperature range 173-393K and in the frequency interval 10(-1)-10(6) Hz, and thermally stimulated depolarization current (TSDC) with a windowing polarization process. Current-voltage (I-V) measurements were also carried out to study interfacial relaxations. Dielectric data were analyzed in terms of permittivity and electric modulus variations. Three relaxation processes (alpha, beta and alpha) have been identified. They were found to be frequency and temperature dependent and were interpreted in terms of the Havriliak-Negami approach. Relaxation parameters were determined by fitting the experimental data. The temperature dependence of the relaxation time was well fitted by the Arrhenius law for secondary relaxations, while the Vogel-Fulcher-Tamann model was found to better fit the tau(T) variations for a relaxation. We found tau(0) = 4.9 10(-12) s, 9.6 10(-13) s and 1.98 10(-7) s for gamma, beta and alpha relaxations, respectively. The obtained results were found to be consistent with those reported in the literature. Due to the calculation of the low-frequency data of dielectric loss by the Hamon approximation, the Maxwell-Wagner-Sillars (MWS) relaxation was highlighted.