Theoretical modeling of the effect of proton donors and regeneration reactions in the network build-up of epoxy thermosets using tertiary amines as initiators

• A structural model describing the epoxy homopolymerization with tertiary amines is presented.
• Expressions for relevant pre-gel and post-gel statistical averages are derived.
• The effect of initiator regeneration and chain transfer is analyzed.
• Protic impurities have a relevant role on the network build-up.

A kinetic-structural model for the curing of epoxy resins with tertiary amines as initiators has been proposed. This model is based on a likely reaction mechanism, which includes the effect of tertiary amine regeneration and the effect of proton donors on the initiation and chain-transfer, and a statistical network build-up methodology based on the independent reactivity of epoxy groups and the random recombination of primary chains. A significant effect of proton donors or impurities is predicted by the model, which can be explained by their likely participation as chain-transfer agents and initiating sites. The occurrence of tertiary amine regeneration has also a profound effect on the curing, but the different regeneration mechanisms have opposite effects and may be counter-balanced. This flexible model is able to explain the curing behavior of different epoxy formulations with tertiary amines as initiator.

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