Diffusion of two associated solvents in various compositions through a swelling polymer material, EVAc (original) (raw)
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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.
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European Polymer Journal, 1994
Swelling of poly(ethylene-co-vinyl acetate) (ESCORENE UL 00218, EXXON Chemicals, Belgium) in solvents of different types has been carried out by the volumetric method at three temperatures. The swelling kinetics are related to the swelling rate constants. A new variable, a', is introduced and defined for comparing kinetic parameters in various polymer-solvent systems. A kinetic model of a reversible first order process was taken as a theoretical model because of the best fitting of experimental data to this model. The solvents are considered from the kinetic (swelling rate constants as indicators) and thermodynamic (equilibrium swelling degree as indicator) points of view. Poly(ethylene-covinyl acetate) interacts with solvents mainly by dispersive forces, but the kinetics of swelling may also be affected by other factors, such as the viscosity and molar volume of the solvent.
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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.
Sorption and diffusion of n-alkanes into bromobutyl rubber membranes
Polymer International, 1995
Sorption and diffusion of n-alkanes into bromobutyl rubber membranes were investigated in the temperature interval 25–60°C by a sorption gravimetric method. The Fickian diffusion equation was used to calculate the diffusion coefficients, which were dependent on the size of the alkanes, their interactions with the chain segments of the polymer and temperature. The diffusion coefficients varied from 0.34×10−7 cm2/s (n-hexadecane) to 9.94×10−7 cm2/s (n-hexane). The activation energy for diffusion varied from 14kJ/mol (n-hexane) heptane to 2.0kJ/mol for n-hexadecane. The sorption/swelling results are discussed in terms of first and second order kinetic equations. The molar mass between chain-entanglement-crosslinks was estimated from swelling data. The experimental and calculated results showed a systematic dependence on the increasing size of the alkanes. None of the solvents showed any degradative effects on the polymer.