THz Spectroscopic Study of Degradation of Epoxy Resins

Two kinds of epoxy resins, HE and SE, were prepared. The resin SE is soft, while HE is hard. After they were heated at 90 °C or higher or irradiated with gamma rays for various periods, their absorption spectra were measured in a frequency range from 0.5 to 5.0 THz. As a result, it has become clear that the intensity of the THz absorption in SE correlates well with the intensity of its mid-infrared (mIR) absorption due to the formation of carbonyl groups. In contrast, HE shows no appreciable changes in both THz and mIR absorption spectra. The above THz absorption can be an oxidation index of epoxy resin.