RELAXATIONS IN THERMOSETS .11. SOLVENT EFFECT ON THE CROSS-LINK NETWORK IN AN EPOXIDE AMINE THERMOSET

Thermosets of the diglycidyl ether of Bisphenol A cured with 4,4'-diaminodiphenylmethane were prepared by mixing the components first in a methyl ethyl ketone solution and second in their pure states. These were studied by differential scanning calorimetry. The T(g) of the thermoset prepared by the first procedure is 30-degrees-C lower in the initial stages of curing than of that prepared by the pure components. This difference is reduced to 15-degrees-C at full cure. The presence of solvent molecules during the early stages of chemical reactions decreases the cross-link density in the ultimately formed network structure, which in turn, as shown in an earlier paper (Polymer 1987, 28, 2023), decreases the rubber modulus of the thermoset.