AbstractPermeability of ethylcellulose and nitrocellulose films to thirteen different gases and vapors was determined. The solubility of these gases and vapors in ethylcellulose and nitrocellulose was also measured by gravimetric and volumetric methods of equilibrium sorption. From these data for permeability and solubility, diffusion coefficients of the gases and vapors in the polymeric films were calculated by means of the relation,P=DS, in whichPandSare the permeability and solubility constants, respectively. It was found that the diffusion coefficientDdecreased linearly with an increase of molecular weight; however, the shape factor of the molecules played an important role in the diffusion process. The solubility constants increased linearly with an increase of the Lennard‐Jones force constants ϵ/kwhen solubility was expressed on a weight basis rather than a volume basis. Both ethylcellulose and nitrocellulose are noncrystalline. Higher solubility, diffusibility, and permeability of ethylcellulose than that of nitrocellulose are considered to be due to the molecular packing in the fil
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