DIELECTRIC STUDIES OF THE CURE OF EPOXY MATRIX SYSTEMS

Dielectric spectroscopy was used to monitor the curing process of two epoxy resin systems. The basic system (system I) consisted of DGEBA(a difunctional epoxy) and a polyamide in a 50-phr mixture. In addition, a comparative analysis was performed on a high-performance resin system (system II) used primarily in unidirectional composite applications. This system contained TGDDM (a tetrafunctional epoxy) and DDS (a tetrafunctional amine) in a 25-phr mixture. The dielectric data were obtained using a simple yet functional sample cell electrode designed and constructed in the laboratory. For system I, isothermal dielectric data were used to determine apparent activation energies for the temperature range from 22 to 70 degree C. The data showed that the activation energy was a function of temperature and increased as the temperature of the cure increased. This indicated that the reaction mechanism was also a function of temperature. For system II, data were collected between 140 and 190 degree C and an overall activation energy for that temperature range was determined. The overall activation energies for both systems, calculated using dielectric spectroscopy, compared favorably to those obtained using differential scanning calorimetry.