Glass transition temperature predictions for non-stoichiometric epoxide-amine networks

The glass transition temperature of various diepoxide-diamine binary or diepoxide/diamine/monoamine ternary systems containing an amine or an epoxide excess, was determined by d.s.c. after complete cure. The copolymer effect of various species such as secondary amines and chain ends, was deduced from Di Marzio's approach7 to the crosslinking effect on Tg and the hypothesis of additivity of the group molar contributions MiTgL−1 of the difunctional groups. The results suggest that all tertiary nitrogens, even branching point ones, act as crosslink points. The chain end contribution depends on their structure but can be considered as constant in a given structural series, thus allowing good Tg predictions with only one adjustable parameter.