Determination of the diffusion coefficients of organic solvents in polyepichlorohydrin: A comparative study of inverse gas chromatography and sorption methods

The diffusivity of organic solvents in polyepichlorohydrin was studied with two different experimental setups: inverse gas chromatography (IGC) with packed columns and sorption measurements in gravimetric experiments monitored in a Cahn electrobalance. The aim of this work was to test the possibility of solving an inherent problem in the data reduction of IGC measurements, that is, the necessity of characterizing the morphology of the polymer coated on the support (usually given in the so-called geometric factor of the column). Temperatures between 35 and 65degreesC were used in the IGC experiments, whereas the sorption measurements were performed between 30 and 40degreesC. Glass beads were used as supports in IGC for obtaining data concerning the variation of the plate height with the average gas velocity, with which the use of the Van Deemter equation allowed the determination of the diffusion coefficient if the geometric factor was known. In the sorption experiments, the diffusion coefficients at different penetrant activities were directly measured. For their extrapolation within the same concentration range used for IGC (infinite dilution of the penetrant), the theoretical model of Vrentas and Duda was used. By a combination of sorption and IGC experiments, the geometric factor of an IGC column could be adjusted, and this allowed the determination of the diffusion parameters of any other solvent in the same column. (C) 2003 Wiley Periodicals, Inc.