Influence of the humidity of the surface electrical conductivity in an epoxy resin

Surface currents were measured with a comb-shaped electrode system deposited on the same side of the sample. The samples were prepared with a diglycidyl ether of bisphenol A resin (DGEBA) cured with isophorm diamine (IPD). The results obtained with dry samples have shown a transitory current essentially due to a dipolar mechanism and, after a time t_p, a permanent current of ionic origin. When the sample was kept in a humid atmosphere, the adsorbed water molecules, bonded to lateral groups in the epoxy resin, increased the duration and the intensity of the transitory currents. On the other hand, ions formed by the water of sorption induce an increase in the permanent current intensity