The dynamic torsional characteristics of a difunctional, bisphenol-A-type epoxy resin cured with different amounts of metaphenylene diamine, using two cure cycles, were determined in torsion at four frequencies between −150° and 200°C. Besides two prominent relaxations, α and β, a third broad, but not very intense, relaxation has been shown to be present in all samples in the intermediate temperature range and has been designated the α transition. An analysis of the data on the temperature and frequency dependence of these relaxations allows some insight into their possible molecular origins. The torsional moduli were found to be related to the molecular packing, as reflected in their densities.
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Gupta et al. (1984) studied this question.
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