Diffusion and solution in high polymers

Abstract

The results of a number of investigations have shown that the diffusion of vapours through high polymers does not conform to Fick's law. This thesis presents data on the diffusion of benzene vapour through films of rubber and of polythene together with a discussion of the deviations from Fick's law. Rates of diffusion and permeation have been measured over a wide range of temperature and pressure. Prom the temperature variation the energies of diffusion and permeation have been calculated. The variation of these rates with pressure has been related to experimentally determined activities and it is shown that the deviations from Fick's law are due to: (1) Non-linear dependence of activity upon concentration. (2) Variation of mobility of the benzene in the polymer with concentration. By making use of a suitably modified form of Pick's law these two factors have been measured, and they have each been examined in the light of approximate theories.