Aging by solvent absorption
Physical aging of polymer materials

Let's consider a sample of initially "pure" polymer material of thickness L, placed at time zero in a medium (gaseous, liquid or solid), containing a single species E soluble in the polymer, the other components of the medium having solubilities in this polymer low enough for their effect to be neglected. Assuming that the penetration of the solvent into the material does not lead to a chemical reaction, irreversible damage or total dissolution of the polymer, an increase in the mass (i.e. concentration of E in the polymer) of the sample will be observed, according to the kinetics shown in figure 3 .