The oxygen permeation rates of the materials were determined
at 50 and 90% RH and 23 ◦C using a OXTRAN Model 2/21 ML Mocon
(Lippke, Neuwied, Germany). The film samples were first conditioned
at the RH of the experiment in the desiccators described
above. Two identical samples were then placed in the apparatus
for analysis. The samples were conditioned in the cells for 6 h, then
the transmission values were determined every 45 min. After the
permeation tests were completed, continuous permeation experiments
were carried out on each sample to determine the diffusion
coefficient (D). From the transmission rate values measured during
the transient state, the value of D was assessed from the solution
to Fick’s second law for the boundary conditions of an isostatic
permeation experiment