Dielectric relaxation of glass-forming epoxy resin under high pressure

Measurements of relaxation time in epoxy resin [poly(bisphenol $A$-co-epichlorohydrin), glycidyl end capped] in the supercooled liquid state have been carried out using dielectric spectroscopy over the frequency range from 10 mHz to 10 MHz as a function of pressure (up to $p=250\mathrm{}\mathrm{MPa}$) and as a function of temperature. To our knowledge, this is the first time a two-dimensional surface of relaxation times $\tau =\tau \mathrm{}(T,p)\mathrm{}$ in epoxy resin has been plotted. The pressure and the temperature dependence of structural relaxation times are in good agreement with the extended Vogel-Fulcher-Tammann equation. For isobaric data, the fragility of the epoxy system reveals a tendency to decrease at elevated pressures. By using pressure as an additional variable, the influence of pressure on glass transition temperature $T_g$ has been determined.