DETERMINATION OF GLASS TRANSITION-TEMPERATURE FROM VISCOSITY AND CONDUCTIVITY MEASUREMENTS FOR AN EPOXY-AMINE SYSTEM DURING CURING

The melt viscosity and the direct current (de) conductivity have been investigated for three bisphenol-A novolac-type epoxide oligomers (PGEBANs) that have some branching in each molecule in comparison with the diglycidyl ether of bisphenol-A (DGEBA) oligomer without branching. The novolac-type PGEBAN oligomer has an experimental relationship between the melt viscosity (eta) and the dc conductivity (sigma), sigma.eta(k) = const, which is the same form observed for the DGEBA oligomer. The exponent k has a linear relationship with the glass transition temperature (T-g) for the two types of oligomers with and without branching. The T-g dependence of k for the epoxide oligomers was used to analyze the T-g of a DGEBA-amine system that had some degree of branching in the molecule based on the bisphenol-A structure. The T-g of the DGEBA-amine system, which was calculated from the k that had been nondestructively determined from the viscosity and the conductivity measurements, was consistent with the T-g experimentally measured by differential scanning calorimetry (DSC). (C) 1993 John Wiley & Sons, Inc.