Permeation of high‐pressure gases in poly(ethylene‐co‐vinyl acetate)

Abstract

A previously proposed theoretical treatment to elucidate the pressure dependence of gas permeability is improved in order to apply it to polymer-gas systems in which gas dissolution follows the Flory-Huggins equation. Permeation rates of N2, CH4, and COz in poly (ethyleneco-vinyl acetate) are measured in the pressure range below 90 atm at 1O-4O0C, and the effect of pressure on permeability is found for each gas. The data are analyzed using the improved method to estimate the contributions of concentration and hydrostatic pressure to the pressure dependence of permeability. The concentration effect decreases with increasing temperature, whereas the hydrostatic-pressure effect is almost independent of temperature. Crystallinity dependence of the concentration effect is discussed in connection with high-pressure permeation data of other semicrystalline polymers reported elsewhere.

Transport Properdines of Gases in Polymers: Bibliographic Review

“…V * being dependent on the molecular size of the penetrants, the following relation is proposed (Naito et al, 1993): (65) d -is the average molecular diameter of the gas, A a constant and n a constant between 2 and 3 (for LDPE and PP). As for α, it is proportional to the partial molar volume and then, to the penetrant diameter.…”

“…The first one of these two mechanisms tends to retard the diffusion process by reducing the segmental motions whereas the second enhances it. Naito et al (1991Naito et al ( , 1993Naito et al ( , 1996 have investigated the pressure effect (up to 10 MPa) on the permeability of some pure gases (with various molecular sizes and solubilities) in rubbery polymers such as PE, PP, poly(ethylene-co-vinyl acetate) and polybutadienes. To describe simultaneously both opposite effects related to pressure, they proposed, at a given temperature, the following model:…”

Analyse et simulation de l'influence de la température et de la pression sur les coefficients de transport du CO2 dans du PVDF

“…Le premier effet entraîne une forte diminution de la vitesse de diffusion des molécules alors que le second accé-lère ce phénomène. Pour décrire ces deux effets, D 0 * (p) peut s'exprimer sous la forme : Naito et al (1996) : (5) seulement valable pour des pressions ne dépassant pas 10 MPa (Naito et al, 1993(Naito et al, , 1996. L'évaluation des effets de couplage entre la température et la pression sur le coefficient β(T, p), caractérisant l'influence de la concentration, est effectuée.…”

“…Ceci est confirmé par Naito et al (1993Naito et al ( , 1996. Dans le tableau 8, les valeurs numériques des différents paramètres intervenant dans l'équation (4) sont récapitulées.…”

Diffuso-Kinetics and Diffuso-Mechanics of Carbon Dioxide / Polyvinylidene Fluoride System under Explosive Gas Decompression: Identification of Key Diffuso-Elastic Couplings by Numerical and Experimental Confrontation

“…The diffusion in turn plasticizes the macromolecular chains involving a larger free volume. Naito et al [22,23] have studied the permeability of a series of pure gases into polymers in the rubbery state, such as polyethylene, polypropylene, and polybutadienes. The effect of gas pressure was carried out up to 10 MPa.…”