TSDC in epoxy networks of well-controlled architecture - Experimental evidence for local and non-local relaxation process

Local and non-local relaxation processes were distinguished by investigatin g the heating rate dependence of the thermally stimulated discharge current (TSDC) line-shape in the case of three epoxy networks of well-controlled a rchitecture. These networks were chosen because their chain dynamics differ by the relative extent of their local and short-scale cooperative molecula r motions, as a consequence of marked differences in crosslink density. As far as local motions are concerned, the TSDC evolution measured at low temp erature can be accounted for by using a model based on a distribution of ac tivation energies. On the other hand, the higher temperature part of the sp ectrum of the densely crosslinked network, which mainly results from cooper ative motions, shows a much different behavior which cannot be fitted by su ch a distribution model.