Concentration and temperature dependence of diffusion coefficients for systems polymethyl acrylate and n-alkyl acetates

Abstract

Experimental data for the intrinsic diffusion coefficients 9 of methyl acetate, ethyl acetate, n-propyl acetate, and n-butyl acetate in polymethyl acrylate (P.M.A.) have been obtained as functions of penetrant concentration over a range of temperatures well above the glass transition point of pure P.M.A. For the four penetrants studied, plots of log 9 against ZQ are linear over the range of v1 at high temperatures and show downward curvature at low temperatures, where 7.11 is the volume fraction of penetrant. The apparent activation energies for diffusion, calculated from temperature dependence data for 9 at zero concentration, are approximately the same for all acetates and decrease continuously with increasing temperature. When compared at the same temperatures, these energies are smaller by a constant factor than the apparent activation energies for the viscous flow of pure P.M.A. Based on an equation for the molar friction coefficient of the penetrant, which is similar in form to the Doolittle viscosity equation, a theory is developed for temperature and concentration dependences of 9 for organic vapour into rubbery polymeric solids. Tests of it are made with the data from the present study as well as those from some previous works. In all cases examined, fairly good agreement between experimental data and predicted relations is obtained.

Transport Properdines of Gases in Polymers: Bibliographic Review

“…One of the most promising and earliest free volume models was developed by Fujita. Fujita (Fujita et al, 1960;Fujita and Kishimoto, 1961) suggested the molecular transport to be due to a redistribution of free volume and not due to a thermal activation. The basic idea of this theory is that a diffusing molecule can only move from one position to another when, in its neighbourhood, the local free volume exceeds a certain critical value.…”

“…However, Fujita et al (1960) considered it inappropriate for the diffusion of small molecules like water in rubbery polymers, which is largely independent of the concentration. Kulkarni and Stern (1983) studied the diffusion of CO 2 , CH 4 , C 2 H 4 and C 3 H 8 in PE (φ a = 0.552) at 5°, 20°and 35°C for pressures reaching 4 MPa.…”

“…The concentration dependence of D can be represented by: Fujita et al (1960) proposed a similar relation from considerations based on the free volume theory. Concerning the solubility coefficient, speaking about its dependence on concentration or on pressure is equivalent because one has the general relation:…”

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

“…Fujita et al [19] have proposed a similar relationship from considerations based on the free volume theory.…”

Nanomembrane Materials Based on Polymer Blends

“…The shape and size of a penetrant molecule will influence the rate of transport within the polymeric matrix. Some researchers have reported a decrease in diffusivity with an increase in the size of the penetrant [24][25][26]. The transport and diffusion in filled polymers depend on the nature of the filler, the degree of adhesion and their compatibility with the polymer matrix.…”