MODEL FOR DIFFUSION OF LOW-MOLECULAR SUBSTANCES THROUGH POLYMERS

A model for diffusion of low-molecular substances through polymers is proposed. The model is based on the idea that the diffusion kinetics i s affected by the relaxation of a polymer matrix. Well-known diffusion types such as Fickian diffusion, Fickian diffusion with relaxation, ' 'case 2'' diffusion, anomalous diffusion, diffusion accompanied by dam ped oscillations of the weight of diffusant transported into the polym er, and ''supercase 2'' diffusion are considered. It is shown that the se types of diffusions are particular cases of the relaxation model pr oposed. Possible reasons and a sequence of steps in which one type of diffusion can follow after another are discussed.