Modelling of condensation reactions in an amine-cured epoxy system with groups of unequal reactivity

A simple model is presented to simulate the process of network formation involving bifunctional epoxies and amines. This model takes account of different reaction rates of the primary and the secondary amines. At the start of the reaction, the amine could either be a mixture of primary and secondary amines or only primary amine, but as a hydrogen of a primary amine is consumed during the reaction, the other hydrogen becomes secondary. The principal effects of the higher reactivity of the primary amines are: (a) increased extents of reaction are required to reach the gel point, with this extent being dependent on the initial stoichiometry; and (b) increased number of less branched species are generated during the reaction.