Effects of Stoichiometric Mixing Ratio on Epoxy Cure —A Dielectric Analysis

Abstract

The goal of this study was to investigate the effects of epoxy/amine mix ratio on cure through the use of real time dielectric response. Microdielectric sensors were used to monitor molar mix ratios of EPON 828/DDS ranging from 3/1 to 1/3. Microdielectric results show that dielectric constant varies from about 9 to 30 with increasing DDS content in uncured resin. Times to the 10 kHz dipole loss peak during cures at 177°C are found to decrease with increasing DDS content. Above a ratio of 2/1 and below 1/2, due to the low molecular weight of the reaction products, loss peaks do not occur. Ionic conduction is shown to have a strong correlation with calorimetric kinetic cure data. The influence of both excess amine and excess DDS is to produce cured material with high ionic conduc tion levels. Deviations from ideal stoichiometery as small as 1.1/1 produce noticeable dif ferences in the finally cured network.