In order to investigate the kinetic of the diffusion of a liquid in a polymer matrix, the study of the diffusion oF the n-heptane in ethylene vinyl acetate is carried out. The polymer considered has a spherical shape. The kinetics of absorption and desorption of the Iiquid are carried out experimentally by weighing the bead at successive times. Thus the experimental curve is compared to the calculated curves using the analytical and numerical solutions. Two numerical solutions, based on finite differences are suggested:
1. Numerical solution for the bead without swelling
2. Numerical solution for bead with swelling and subsequent change in dimensions.

The second purpose seems being the better and give a good agreement with the experience since the diffusivity (experimental and calculated) are of the same magnitude.