Separation of gaseous mixtures by permeation through polyethylene film

The permeation of polyethylene film by carbon dioxide, ethane, and propane at elevated pressures was investigated. In addition, the separation of mixtues of ethane and propane by permeation was studied. Both hydrocarbon vapors' permeation exhibited pressure dependence, with propane showing the greatest variation over the same range. In the case of the mixture separation study, the achieved degree of separation was lower than would be predicted on the basis of the pure component permeation constants. Moreover, the total flow of vapor through the film was greater than would be expected on the basis of the individual gas flows. This was attributed to an anomalous diffusion phenomenon of ethane in the presence of dissolved propane due to a plasticization of the polymer network.