Permeability of Gases Through Filled and Unfilled Rubber Membranes

Permeation experiments were conducted to study the structural differ- ences between synthetic poly-cis 1,4-isoprene SNR and natural rubber NR, as well as differences resulting from filling with carbon black. The study aimed further at testing Frischs theory of isotope effects in activated diffusion and on the unit size of the free volume in rubbers. The rubber samples consisted of thin crosslinked sheets of NR AND SNR. The carbon content in the filled samples was 16 by volume. The permeation rate of hydrogen and deuterium through filled and un-filled NR and SNR were measured by the time-lag method as a function of temperature and pressure 40-85 C and 1-55 cm of Hg. The permeability coefficient, p, diffusion coefficient, d, and solubility, s, thus deduced were further used to evaluate the energies of activation for permeation and for diffusion, and the heat of solution according to the Arrhenius equation. The results show that hydrogen has generally a higher permeability and diffusivity than deuterium and that the permeabilities or diffusivities are markedly reduced by the presence of the filler.