In situ study of the temperature activated kinetics of water sorption in an epoxy varnish

The dielectric permittivity of a polyepoxy varnish with glass transition temperature (Tg) 61 °C is monitored during immersion in 0.5 M NaCl aqueous solution, by electrochemical impedance spectroscopy, at various temperatures the range [21; 78] °C. sorption curves are first analysed Fickian approach. An Arrhenius-type dependence apparent coefficient diffusion observed, no visible influence Tg. Below 46 °C, clearly do not obey Fick′s second law diffusion. On another hand, Kohlrausch-Williams-Watts function (KWW) satisfactorily fits all isothermal curves. KWW time constant has same activation as diffusion, and likewise unaffected stretching exponent displays strong on Tg, correlates behaviour observed rubbery state, thought to be governed molecular heterogeneities network. A linear rule mixture used estimate water uptake temperature. originality this work lies situ analysis kinetics (constant immersion), which performed above (rubbery state) below (glassy Tg coating.