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

Abstract

ABSTRACT: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 65°C were used in the IGC experiments, whereas the sorption measurements were performed between 30 and 40°C. 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.

Diffusion Behavior of Water at Infinite Dilution in Hydroxypropyl Xylan Films with Sorbitol and Cellulose Nanocrystals

“…22 Following the Arrhenius behavior simply suggests that the water molecules exhibited a hopping diffusion mechanism as described in the free volume theory. 21 Table 4 summarizes the activation energy values determined based upon the data shown in Figures 8 and 9. Over the temperature range of interest, activation energy decreases with increasing concentration of sorbitol.…”

“…In order to measure the diffusion coefficient at infinite dilution, the Van Deemter equation was used. 21,22…”

“…At infinite dilution, retention time of the probe is independent of concentration, and the concentration of probe molecules in the stationary phase is in equilibrium with that of the gas phase. In order to measure the diffusion coefficient at infinite dilution, the Van Deemter equation was used. , where H is the equivalent theoretical plate height that is determined from the widths of the eluting peaks for different carrier gas flow rates, and u is the average linear carrier gas flow rate. A is attributed to the eddy diffusion that is defined as 2 λd p .…”

Effect of Humidity on the Permeability of Alcohols in Hydroxypropyl Xylan Films

“…Van Demeter equation was used to obtain diffusion coefficients. The equation has been described in our previous work as well as some other studies by Etxabarren et al and Kalaouzis and Demertzis . Van Deemter curves were obtained by plotting height equivalent to theoretical plate, H , (from peak widths and retention times) versus linear velocity of carrier gas, V .…”

Determination of the infinite dilution diffusion and activity coefficients of alkanes in polypropylene by inverse gas chromatography

“…The molecular transport of small moleculars in polymer sheet membranes is of considerable importance in a wide variety of manufacturing operations of polymers 1, 2. Accurate measurements of the activity coefficients and diffusivities for small molecules in polymers have been a very difficult but important issue for many years.…”