Reaction and characterisation of a two-stage thermoset using molecular dynamics

Abstract

The two-stage curing reaction of unsaturated polyester polyurethane hybrid resins is modelled using all-atom molecular dynamics simulations. The reactions – a urethane reaction and a radical polymerisation – are modelled based on atom distances and probabilities calculated by an Arrhenius law, without the need for intermediate minimisation steps. As representatives of this thermoset class two resin systems are considered. First, a simple virtual resin with just enough structure to be capable of the described reactions is used to verify the reaction process. Second, a system is studied which is designed to be similar to a commercially available hybrid resin used in conjunction with fibre reinforcements. Both systems are simulated and the results are used to evaluate the chemical reaction process and then to identify the resulting material's macroscopic properties and behaviour. These properties are determined at different cross-linking stages of the curing process providing a unique insight into the development of these parameters during the chemical reaction.