Dynamics of epoxies: a full dielectric analysis by wideband spectroscopy

The dynamics of monoepoxide (CGE) and diepoxide (DGEBA) compounds, investigated by wideband (10(2)-10(10) Hz) dielectric spectroscopy from below to above the glass transition temperature in the range 130-360 K, shows a bimodal relaxation and the presence of a de conductivity contribution. The fitting of the data by the Havriliak-Negami function provided the temperature behaviour of conductivity, relaxation times, dielectric strengths and shape parameters. The glass transition phenomenon was detected by the changes of both the relaxation strength and the low frequency slope of the secondary relaxation, and a transition temperature T-B > T-g between two different relaxation regimes, coincident with the splitting temperature of the systems, was also recognised, The comparative analysis of the results draws an overall picture which improves our information on the dynamics of the systems and also supports some recent ideas on the splitting between main and secondary relaxations. (C) 1998 Elsevier Science B.V. All rights reserved.