DIFFUSION OF A CHEMICAL THROUGH THE LIQUID LOCATED IN A POLYMER - MODELING AND EXPERIMENTS

When a polymer is put in contact with a liquid, some matter transfers may take place, following rather complex processes. The case considered here is a polymer initially saturated with liquid through which a chemical diffuses. The problem is thus the diffusion of the chemical through the liquid located in the polymer, and the determination of the diffusivity. A method for measuring the diffusivity is developed and tested by using the three-step technique: immersing the polymer bead in the liquid so that it becomes saturated; soaking the pre-saturated bead in the same liquid containing a small amount of the chemical; and determining the kinetics of release of the chemical out of the bead when the bead is re-immersed into the same pure liquid. The process of release of the chemical is controlled by diffusion. The diffusivity is obtained from the experimental kinetics, and the accuracy of this value is tested by comparing the experimental and calculated kinetics of release of the chemical.