Influence of thermal diffusion on the solvent absorption kinetics of highly cross-linked epoxy resins

The influence of heat transfer on the solvent absorption kinetics of an epoxy o-cresol novolac resin composite which is applied for the encapsulation of heat emitting devices is investigated theoretically. The fundament of the model is the PC-SAFT equation of state which is extended by a network term for including the arising elastic forces in the epoxy resin network. PC-SAFT supplies an expression for the chemical potential which is the driving force in a non-equilibrium thermodynamic approach to account for the coupled heat and mass transfer. With this model, it is investigated how the influences of the solvent absorption kinetics due to thermal diffusion depend on factors such as the temperature gradient, the polarity and state of the solvent. It was found that in heat induced polymer matrices, the coupling of mass and heat transfer cannot be neglected. For the first time, it could be shown by the application of PC-SAFT in a non-equilibrium thermodynamic framework, that there is a large influence of the solvent polarity on the thermodiffusion.