The influence of ions on water transport in nylon 6 films

Nylon 6 films are directly exposed to saline solutions containing mono-valent ions and the water uptake is measured with magnetic resonance imaging (MRI). Both the amount of water uptake and the rate of water uptake are studied. First, the films are exposed to solutions with different concentrations of NaCl. Later, solutions of salts such as LiCl, KCl and KNO3 are used. It is shown that all salts act similar. They reduce the amount of water ingressing the nylon film and also slow down the rate of uptake. It seems that water uptake can be predicted by knowing the activity of the salt solution on top of the nylon film. Element analysis shows that ions migrate into the nylon film. Although ions do enter the film, their amount is not large enough to influence the diffusivity and chemical potential of water in the nylon film.