Permeation of Oxygen and Nitrogen Gases through Poly(ethylene-co-vinyl acetate) Membranes

The transport of oxygen and nitrogen gases through uncrosslinked and crosslinked poly(ethylene-co-vinyl acetate) membranes has been analyzed. Poly(ethylene-co-vinyl acetate) was crosslinked by dicumyl peroxide and benzoyl peroxide. Neat sample showed a lower permeation coefficient due to the crystalline nature. The crystalline nature was supported by X-ray diffraction analysis. The difference in the permeation behavior of the two crosslinked samples was correlated with crosslink density. Crosslink density was calculated using equilibrium sorption method. Differential scanning calorimetry analysis also supports the different permeation behavior of the crosslinked samples. The O-2/N-2 selectivity of the membranes was estimated. The influence of the crosslink density and size of penetrants on permeation were analyzed. The effect of free volume on the gas barrier properties was investigated by positron annihilation lifetime spectroscopy.