The work reported here consists of an investigation of the dynamics of the glass transition and secondary relaxations in terms of possible epoxy network’s molecular structure variations induced by variable cure heating ramp rates or after immersion of cured samples in acetone. A dielectric loss permittivity maximum at frequency (fmax) for the sub-Tg δ peak was found to shift to higher values with increasing temperature in Arrhenius fashion. This relaxation was assigned to phenyl ring flipping in the main DGEBF chain facilitated by the presence of adjacent flexible ether linkages. Effect of acetone ingress on the epoxy network’s sub-Tg and Tg motions will be presented. As shown in the enclosed Figure, values of the Tg relaxation peak maximum were found to shift upwards with increased immersion time of the cured samples in acetone. This would reflect faster Tg relaxation motion with increased acetone ingress due to plasticization. Distribution of relaxation times, G(τ) will be extracted from the fitted spectra and values will then be related to differences in molecular weight between crosslinks (Mc) within the epoxy networks.

Dielectric spectroscopic analysis of cure behavior and relaxation processes in polymer composites

249th National Meeting (2015)

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