Thermoset materials frequently display non-classical moisture sorption behaviors. In this paper, we investigated this issue from an experimental point of view as well as in terms of modeling the water transport. We used the gravimetric technique to monitor water uptake by epoxy samples, with several thicknesses exposed to different levels of humidity during absorption and desorption tests. Our results revealed that the polymer displays a two-stage behavior with a residual amount of water that is desorbed progressively. We proposed a phenomenological reaction-diffusion scheme to describe this behavior. The model describes water transport as a competition between diffusion and the reaction, during which the local diffusivity and solubility depend on the local advancement of the reaction. We then implemented our model using COMSOL Multiphysics and identified it using a MATLAB-COMSOL optimization tool and the experimental data. We discussed the relation between the hydrophilicity of the product of the reaction and the diffusion behavior. We examined the reaction-induced modification of the water concentration field. It is worth noting that part of the phenomenology can be explained by the presence of hydrolyzable groups.

In this paper, we studied the water transport in thermoset matrices. We used Fourier Transform Infrared analysis (FTIR) during sorption/desorption experiments to investigate the interaction between sorbed water and the epoxy network. Our results demonstrated that the polymer matrix undergoes hydrolysis. We found that the chemical species involved in the reaction process was the residual anhydride groups. These results support the physical basis of the three-dimensional (3D) diffusion/reaction model. We finally showed that this model is able to reproduce multi-cycle sorption/desorption experiment, as well as water uptake in hybrid metal/epoxy samples. We simulated the 3D distributions of the diffusing water and the reacted water.International audienceIn this paper, we studied the water transport in thermoset matrices. We used Fourier Transform Infrared analysis (FTIR) during sorption/desorption experiments to investigate the interaction between sorbed water and the epoxy network. Our results demonstrated that the polymer matrix undergoes hydrolysis. We found that the chemical species involved in the reaction process was the residual anhydride groups. These results support the physical basis of the three-dimensional (3D) diffusion/reaction model. We finally showed that this model is able to reproduce multi-cycle sorption/desorption experiment, as well as water uptake in hybrid metal/epoxy samples. We simulated the 3D distributions of the diffusing water and the reacted water

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