Effect of water presence on the sorption of organic compounds in ethylene–vinyl alcohol copolymers

Abstract

Sorption isotherms of methanol, ethanol, propanol, butanol, hexanol, ethyl caproate, and limonene in 4 ethylene-vinyl alcohol (EVOH) copolymers with different ethylene contents were determined by inverse gas chromatography (IGC) at 25°C and different relative humidity conditions. From sorption isotherms, solubility coefficients were determined and used as a tool for comparison. Besides affecting the morphology of the polymers by plastification, sorbed water seems to increase the polarity of the medium. Sorption of alcohols increases at high relative humidity; both plasticization and polarity cause this behavior. The effect is more important for the smaller alcohols and among polymers for those with low ethylene content. As the sorbant becomes nonpolar, plasticization and polarity effects become antagonistic. Indeed, the effect of water presence in sorption of hexanol is not significant, and sorption of limonene and ethyl caproate is even reduced at high water content.