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Dielectric measurements of an epoxy resin, N, N-diglycidyl-4-glycidyloxyaniline, have been carried out in the supercooled and glassy phase over a broad frequency range (10 2-6 109 Hz). The measurements reveal electrical transport due to ionic impurities as well as three different dipolar relaxations—in addition to the - and -relaxation, a slower 0 -relaxation is recognized, whose loss peak is disclosed after subtraction of the dc conductivity contribution. The glass transition is found to affect markedly the secondary relaxation, whose strength and shape parameters change across Tg. The major inference from the results concerns the existence of a transition in the dynamics, occurring some tens of degrees above Tg, in the vicinity of the temperature TS where the peaks of the - and -relaxations merge. Evidence in favour of such a transition is given by: (i) the change in the temperature dependence of the -relaxation time; (ii) independently, the change in the temperature dependence of the dc conductivity; (iii) the breakdown of the Debye-Stokes-Einstein model, replaced at lower temperatures by a fractional regime. Concerning the 0 -process, it shows a Vogel-Fulcher behaviour with the same temperature T0 as the -relaxation but, unlike this last, it is not involved in a splitting phenomenon with the -relaxation. Several hypotheses concerning the nature of the 0 -process are explored.

The conductivity and dielectric relaxation behaviour of a glass-forming monoepoxide, cresyl glycidyl ether (CGE), were studied from to by impedance spectroscopy, in the temperature interval 83 - 333 K. Data analysis indicated the existence of a transition temperature marking the separation between two different relaxation regimes, in accordance with previous results given by Stickel and co-workers. The temperature is well above the glass transition temperature , and coincides with the temperature at which the timescales of the main and secondary relaxation processes coincide, so at there is a unique overall relaxation process. The splitting layout of CGE differs from that of the very common diepoxide diglycidyl ether of bisphenol-A (DGEBA), studied previously, and also the relaxation at high temperature has a correspondingly different dynamical behaviour. The relaxation strength behaviour is also analysed and compared with that of DGEBA; the similarities are discussed.