Vitrification, devitrification, and dielectric relaxations during the non-isothermal curing of diepoxy-cycloaliphatic diamine

摘要

The curing of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with a diamine based on 4,4'-diamino-3,3'-dimethyldicyclohexylmethane (3DCM) was analyzed by dielectric relaxation spectroscopy (DRS) between -100 and 220 degrees C, at heating rates ranging from 0.1 to 2 K min(-1). The permittivity, epsilon', and the loss factor, epsilon", were measured by DRS in the frequency range between 1 and 100 kHz. The dielectric relaxations were correlated with the relaxations observed previously by temperature modulated differential scanning calorimetry (TMDSC) at the same heating rates and in modulation conditions of amplitude 0.2 K and a period of 60 s, which is equivalent to a measuring frequency of 16.7 mHz. The di-electric measurements showed three frequency-dependent dipolar relaxations and one ionic relaxation, which was independent of the frequency. The dipolar relaxations were associated with the glass transition of the unreacted system and the vitrification and the devitrification processes of the system during the crosslinking reaction, and the ionic relaxation was associated with the beginning of the crosslinking reaction. (c) 2006 Wiley Periodicals, Inc.