Quantitative approach for the prediction of preferential sorption in the case of pervaporation of a physico-chemically similar binary mixture (original) (raw)
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Sorption experiments are often conducted in gravimetric sorption columns where several deviations from ideal conditions could potentially occur. For example, heat effects due to solvent sorption, errors introduced due to concentration dependent diffusion coefficients and swelling are unavoidable. In this study, we develop a model to study the importance of the combination of these effects in obtaining diffusion coefficients from sorption experiments. The model is used to explore a wide range of operating conditions and physical parameters.
Sample-dimension effects in the sorption of solvents in polymers — a mathematical model
Journal of Membrane Science, 1978
It has recently been reported in the literature that, given a polymer-solvent pair, different sorption behaviors are observed according to the size of the sample. A mathematical model is developed for the coupled swelling-diffusion phenomenon in the polymer sample, which allows the prediction of such sample-dimension effects. Five different kinds of behavior are predicted for a given polymer-solvent pair, and the corresponding size bounds are related to the relevant physicochemical properties of the system. Comparison with a large body of literature data is satisfactory.
The influence of permeant properties on the sorption step in hydrophobic pervaporation
Journal of Membrane Science, 2003
Liquid solubility measurements were performed by immersion of poly(octyl)methylsiloxane (POMS) in dilute aqueous solutions of homologous series of aliphatic esters and alcohols with compound specific concentrations of 20, 40, 80 and 120 ppm. Measurements were performed at 20 • C with both single-and multi-compound mixtures and linear sorption isotherms were obtained. By fitting experimentally determined molar solubility coefficients to their liquid molar volumes, exponential relationships were obtained for compounds within the same chemical group. The solubility coefficients of alcohols were smaller than those obtained for esters of approximately the same molecular size due to the hydrophilic hydroxyl group in the former. There was evidence of some coupling effects; in the case of larger esters the solubility was higher when they were sorbed from multi-compound solutions of esters. The solubility of all the alcohols except n-octanol was the same regardless of whether they were sorbed from single-or multi-compound solutions. As far as the n-octanol was concerned, the solubility decreased when other alcohols were present in the solution. One possible explanation of this is that the ability of alcohols to form clusters through hydrogen bonding modifies the polymer phase by reducing its ability to take up n-octanol.
Measurement and correlation of vapor sorption equilibria of polymer solutions
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Solvent sorption equilibrium data of binary solventrpolymer systems were measured using a vacuum electromicrobalance. Solvents tested were benzene, cyclohexane, n-hexane, water and methanol. Rubbery Ž. Ž. Ž. polymers tested were poly dimethylsiloxane, PDMS , poly iso-butylene, PIB , poly propylene oxide, PPO and Ž. poly vinyl alcohol, PVA. Data obtained in the present study, together with existing literature data, were Ž E. Ž. correlated by both the UNIQUAC, Gibbs function g-model and a recent volumetric EOS equation of state proposed by the present authors based on a non-random lattice-hole theory.
Sorption phenomena of organic solvents in polymers: Part I
European Polymer Journal, 2005
In this work we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, sixty-one isothermal data sets for forty copolymer + solvent binaries and for fourteen of their parent homopolymer + solvent binaries have been used in the temperature range of 23.5-80°C. Solvents studied are acetone, acetonitrile, 1-butanol, 1,2-dichloroethane, chloroform, cyclohexane, hexane, methanol, octane, pentane, and toluene. Copolymers studied are poly(acrylonitrile-co-butadiene), poly(styrene-co-acrylonitrile), poly(styreneco-butadiene), poly(vinyl acetate-co-ethylene), and poly(vinyl acetate-co-vinyl chloride). All copolymers are random copolymers. Some homopolymers are also studied: polyacrylonitrile, poly(cis-1,4-butadiene), poly(ethylene oxide), polystyrene and poly(vinyl acetate). According to these data sets, solvent weight fraction in the polymer is plotted against solvent vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, v. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, C are used to interpret the equilibrium data.
European Polymer Journal, 2016
In this work, a new methodology to determine the solvent sorption curve (pressurecomposition curves for the vapour-liquid equilibrium) of a polymer/solvent mixture, from the Flory Huggins data measured at the composition extremes of the binary mixture (infinite dilution of polymer, and infinite dilution of solvent) has been proposed. This methodology is based on the works of Bernard Wolf about the dependence of the Flory Huggins parameter, v, on the polymer composition. The methodology was validated for ten different polymer/solvent systems, with an overall value of the Average Absolute Deviation (%AAD) between the literature and estimated pressure values around 1%. Once validated, the procedure was employed to obtain the sorption curves of several systems of interest for our research group: the binary mixtures of ethylene/vinyl acetate copolymer (EVA), the ones of its correspondent homopolymers, polyethylene (PE) and polyvinyl acetate (PVA), with cyclohexane, and the binary system polyvinyl acetate/methanol. For these systems, the Flory Huggins parameter values at infinite dilution of solvent and polymer were taken from our previous works (studies of inverse gas chromatography and intrinsic viscosity, respectively). Finally, from the previously obtained values, the dependence of the Wolf parameters on the vinyl acetate percentage was analyzed taking into account the excess properties.
The analysis of sorption data of organic vapors in polymeric membranes through novel theories
Journal of Membrane Science, 1996
Analysis of sorption data of hydrocarbon vapors in polyethylene and polypropylene films using Flory Huggins, UNIFAC, Michael-Hausslein and Flory-Rehner theories are presented. Basically two models are used, one deduced with UNIFAC and Michael-Hausslein (UNIFAC-M-H) approach and the other with UNIFAC and Flory-Rehner (UNIFAC-F-R) theory. Prediction of penetrant activity values through these theories fit quite well the experimental results with errors ranging between 4.7 and 10.8%. The mean arithmetic values of the fraction of elastically effective chain in the amorphous region are,/= 0.4915 and f= 0.3354 for polypropylene (PP) and polyethylene I PE), respectively. The experimental results with polypropylene are correlated, establishing a unique expression to predict solubility and solubility coefficient. The dependence of solubilily in polypropylene over the whole range of temperature it is also presented.
Colloid & Polymer Science, 1993
Flory Huggins theory modified by Pouchly has been applied to predict maxima and minima in the curve of total sorption in ternary polymer systems formed by a polymer and two liquids. In this work, different diagrams based on experimental magnitudes easily obtained such as the difference in affinities of liquids, solvents and non solvents, and the solvent molar volume ratio. Total sorption parameter has been considered to be the decisive magnitude to define extrema conditions in both cosolvent and cononsolvent ternary polymer systems. The theoretical prediction is not altered by the inclusion of ternary interactions. Different examples of ternary systems dealing with vinyl polymers and polydimethyl siloxane have been used to test the above formalism.
The present investigation is concerned with the development of a new iterative method permitting, for a Fickian sorption of a binary liquid mixture in thin polymer sheets, the simultaneous determination of the self-diffusion coefficients of the components of the mixture, and their uptake fractions at equilibrium. The approach is based on a new equation describing a parallel Fickian sorption of the components of the mixture into thin polymer sheets. The procedure was tested with ideal and Monte Carlo simulated data. The method, applied to ideal simulated data that corresponded to various values of D 1 , D 2 and f, perfectly extracted the desired parameters. The application of the method to Monte Carlo simulated data revealed that this method is fairly applicable even when the simulated data are considerably obscured by ''noise''. Finally, the proposed method was successfully applied to the experimental data concerning the sorption kinetics of ethanol-water mixture (75 vol % in EtOH) at 378C in thin polymeric sheets of triethyleneglycol dimethacrylate (TEGDMA).
Sorption mechanism in organic solutions of uncharged polymers
Journal of Applied Polymer Science, 2010
In this work, we use the vapor-sorption equilibrium data to show the degree of solvent upturn in each solvent-polymer system. For this purpose, 20 isothermal data sets for five polymer þ solvent binaries have been used in the temperature range of 298-413 K. Solvents studied are benzene, pentane, hexane, toluene, and chlorobenzene. Homopolymers studied are: polystyrene, poly-(vinyl acetate), polyisobutylene, and polyethylene. According to these data sets, solvent weight fraction in the polymer is plotted against solvent vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory-Huggins theory to obtain dimensionless interaction parameter, v. Also the Zimm-Lundberg clustering theory and non-ideality thermodynamic factor, C are used to interpret the equilibrium data. V