The Self-diffusion of Surface Active Agents in Nylon

Abstract The self-diffusion rates of sodium dodecyl sulfate, sodium tetradecyl sulfate, sulfuric acid and hydrochloric acid in nylon containing various amounts of each solute and their temperature dependence were measured by the surface radioactivity decrease method using 35S and 36Cl. From the experimental results, it has become clear that the diffusion of the solute in nylon is important in the process towards the attainment of sorption equilibrium of these substances by nylon, and in this case the presence of water in nylon is necessary for the diffusion to take place appreciably. The diffusion coefficients were much smaller than those in their aqueous solutions. The diffusion rates of the surface active agents depended little on the concentration in nylon compared with those of the inorganic acids. The diffusion rates of sulfuric acid and hydrochloric acid depended largely on their concentration in nylon. This will be due to a difference of the mechanism of diffusion between the former and the latter. The activation energies of SDS and sulfuric acid for diffusion were considerably great and approximated to those of many substances in solid.