Molecular dynamics of an epoxy resin studied by Thermally Stimulated Depolarization Currents

The Thermally Stimulated Depolarization Current (TSDC) technique has been used to study the molecular mobility of diglycidyl ether of bisphenol-A (DGEBA) in the temperature range from −160 °C up to 10 °C. The molecular mobility in the glassy state and in the supercooled liquid was then characterized. Two secondary relaxations were detected, one of them partially disguised by the main α-process. Differential Scanning Calorimetry (DSC) was used to analyse the dynamics of the structural relaxation around Tg (from the heating rate dependence of the onset temperature of the glass transition signal). The values of the fragility index obtained in this work by TSDC and DSC are compared with the values reported in the literature obtained from other experimental techniques. A relaxation above the glass transition temperature was also observed. The controversy about the attribution of this upper-Tg mobility at the molecular level is reported.