Dipolar relaxations in an epoxy-amine system

Dipolar relaxations in a reactive epoxy-amine system based on diglycidyl ether of bisphenol A with 4,4'-diaminodiphenylsulfone were studied with the Havriliak-Negami function. The system was cured isothermally at 140 degreesC using simultaneous kinetic and microdielectric studies. The relaxation time was calculated from the frequency f(max) of the peak of the loss factor epsilon" versus frequency f. A linear relation exists between the logarithm of the relaxation time tau and the glass transition temperature T-g. Then, log tau follows the Di Benedetto equation revisited by Pascault and Williams allowing the prediction of the relaxation time T during cure. The unrelaxed permittivity at high frequency epsilon(s) the relaxed or static permittivity epsilon(u) and the skewness parameter beta were found independent on the conversion or the curing timed The distribution parameter a decreases as curing time t increases. The difficulty of orientation of dipoles in the electric field due to vitrification is responsible of these behaviours. (C) 2002 Elsevier Science Ltd. All rights reserved.