Influence of the temperature on the dielectric properties of epoxy resins

Electrical degradation processes in epoxy resins, such as electrical treeing, were found to be dependent on the temperature at which the experiments were carried out. Therefore, it is of considerable research interest to study the influence of temperature on the dielectric properties of the polymers and to relate the effect of temperature on these properties to the possible electrical degradation mechanisms. In this work, the dielectric properties of two different epoxy resin systems have been characterized via dielectric spectroscopy. The epoxy resins used were bisphenol-A epoxy resins Araldite CY1301 and Araldite CY1311, the later being a modified version of the former with added plasticizer. The CY1301 samples were tested below and above their glass transition temperature, while the CY1311 were tested well above it. Both epoxy systems possess similar behaviour above the glass transition temperature, e.g. in a flexible state, which can be characterized as a low frequency dispersion (LFD). On the other hand, it was found that below the glass transition temperature CY1301 samples have almost "flat" dielectric response in the frequency range considered. The influence of possible interfacial features on the measured results is discussed.