EFFECT OF WATER PRESENCE ON THE SORPTION OF ORGANIC-COMPOUNDS IN ETHYLENE-VINYL ALCOHOL COPOLYMERS

Sorption isotherms of methanol, ethanol, propanol, butanol, hexanol, e thyl caproate, and Limonene in 4 ethylene-vinyl alcohol (EVOH) copolym ers with different ethylene contents were determined by inverse gas ch romatography (IGC) at 25 degrees C and different relative humidity con ditions. From sorption isotherms, solubility coefficients were determi ned and used as a tool for comparison. Besides affecting the morpholog y of the polymers by plastification, sorbed water seems to increase th e polarity of the medium. Sorption of alcohols increases at high relat ive humidity; both plasticization and polarity cause this behavior. Th e 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, an d sorption of limonene and ethyl caproate is even reduced at high wate r content. (C) 1998 John Wiley & Sons, Inc.