COMPARISON OF UNIQUAC WITH RELATED MODELS FOR MODELING VAPOR SORPTIONIN POLAR MATERIALS

By a systematic investigation of solvent polymer systems of even great er complexity, this work analyses the relative performances of UNIQUAC and related models to account for sorption phenomena in polar elastom ers (polyurethaneimides) with vapours of moderate to strong polarity ( ether, ester, alcohol). Four different UNIQUAC-type models have been c hosen for this study: UNIQUAC, UNIQUAC-HB, UNIQUAC-FV and UNIQUAC-FV+H B. They mainly differ in corrective and/or additional terms accounting for particular effects such as free volume (FV) effects or hydrogen b onding (HB) or a combination of both (FV+HB). Their main respective ad vantages are discussed with regard to the solvent and polymer chemical structures and the type of interactions involved in the sorption phen omenon. UNIQUAC-FV is shown to provide the best results for the sorpti on of aprotic species (ether, ester) in polyurethaneimides, as could b e expected for elastomers for which free volume effects are usually be lieved to be significant. However, the sorption of a protic species (a lcohol) is best described by UNIQUAC-HB, i.e. the UNIQUAC model specif ically modified for systems involving strong interactions by hydrogen bonding. Hydrogen bonding could therefore prevail on free volume effec ts for these particular systems. (C) 1998 Elsevier Science B.V. All ri ghts reserved.