Dynamics of an epoxy system near the glass transition studied by Brillouin and dielectric spectroscopies

The relaxation processes of an epoxy resin were investigated by light scattering and broadband dielectric spectroscopy around the glass transition temperature T-g. Dielectric spectroscopy measurements give evidence of two relaxations, a structural and a secondary one, merging into a single process well above T-g. Besides the regular divergence of the structural relaxation time, the glass transition is also evidenced by changes of the shape parameters and of the relaxation strength of the secondary process. A comparison between dielectric and Brillouin data shows that Brillouin spectra are markedly sensitive to the secondary relaxation.