Liquid sorption by rubber sheets and evaporation; models and experiments

The sorption of liquid by rubber sheets has been considered as a diffusion process controlled by a constant diffusivity. In spite of the swelling, the thickness of the sheet may be assumed to remain constant for integrating Fick's law as diffusion proceeds. The evaporation of liquid from the rubber is diffusion controlled. No analytical solution can be obtained in general cases. A model is described, based on an explicit method with finite differences, taking into account the diffusivity and rate of evaporation. This model gives results for desorption in good agreement with experiments in the case of motionless air and with stirring. Results with high stirring can also be obtained by analytical solution of Fick's law integrated by taking zero for the concentration of liquid on the rubber faces at the start of the process.