Modelling the diffusive behavior of polymer foam immersed in water

This study introduces a refined methodology for modeling water diffusion in polymeric foams. The approach is grounded in Darcy’s law, which governs diffusion in porous media. A modified diffusion law is proposed to describe the complex interplay between the foam’s mechanical state and the dynamics of water transport. The resulting diffusion kinetics follows a three step mechanism controlled by a parameter that captures the interaction between Darcy-governed diffusion and diffusion influenced by mechanical properties. Notably, at low values of this parameter, the kinetics closely approximate those predicted by Fick’s laws. The framework is further extended to sandwich structures composed of composite skins and a polymer foam core. In this configuration, the diffusion process proceeds in two distinct phases: an initial pseudo-step corresponding to skin saturation, followed by diffusion within the foam core. A series of experimental studies corroborate this intricate diffusive behavior, underscoring the robustness and applicability of our model.