The permeability of poly(ethyl methacrylate) to gases and water vapor

Abstract

AbstractThe permeabilities, diffusivities and solubilities of He, Ne, A, O2, N2, Kr, CO2, H2S, and H2O in poly(ethyl methacrylate) have been measured above and below the glass temperature. Water showed a small increase in solubility when the polymer was heated above the glass temperature. Water also showed anomalous behavior in that the solubilities calculated from the permeability constants and the time‐lag diffusion constants are much less than those measured by direct weighing. The behavior had been found previously with other polymers and has been interpreted in terms of the clustering of water molecules in the polymer. The Arrhenius plots of the permeability and diffusion constants for water showed the change in slope at the glass temperature reported to occur with many gases and vapors through other polymers. The gases, however, showed no change in slope even with large molecular size gases such as silicon tetrafluoride and sulfur hexafluoride. The results found with water are interpreted as due to the plasticizing effect of the penetrant when the polymer is above the glass temperature. In the case of the gases, the lack of a transition effect is interpreted in terms of the relative sizes of the gas molecule and the average hole she of the polymer. The energies of activation for diffusion were found to be proportional to the 1.6 power of the molecular diameter of the; penetrants, i.e., intermediate between that found for rubber and for both poly(vinyl acetate) and poly(ethylene terephthalate).