Toluene diffusion in butyl rubber

Abstract

The sorption isotherm and the polymer mass‐fixed diffusion coefficients, D, for toluene in butyl rubber have been measured by the incremental sorption method to concentrations of 130%, corresponding to a solvent volume fraction of 0.578. The increase in D with concentration is strongly exponential to a concentration of 30% and then begins to level out. Since the nature of the dimensional change occurring in vapor sorption was not known, the values of D were converted to solvent self‐diffusion coefficients, D1, assuming both swelling in the thickness direction (1D) and isotropically (3D). The free volume (FV) theory of Fujita was fitted to the resulting D1 with the zero concentration diffusion coefficient and the self‐diffusion coefficient of toluene as limiting values leaving only a single arbitrary parameter. In this form the FV theory was able to describe the trend of the experimental D1 for the 1D and 3D cases equally well. Values of D were back‐calculated from the FV relations for the 1D and 3D cases for comparison with the experimental results and with the diffusion coefficient determined by immersion in toluene. These comparisons favor the assumption that swelling is isotropic. It appears that the simple free volume relation is capable of providing a satisfactory representation of the experimental data with only a single fitting parameter, although there are moderate quantitative discrepancies. © 1994 John Wiley & Sons, Inc.

Free-volume microprobe study of iodine diffusion in polymers

“…This simple theory has been tested and found to describe satisfactorily the diffusion of a number of organic liquids and vapours in polymer solutions 14. Recently, Schneider et al 15 have shown that the diffusion of toluene in butyl rubber follows the predictions of the Fujita's free‐volume theory 11. 13 It should be noted here that, in these studies, the free‐volume of the polymers was obtained through indirect methods.…”

Water Sorption Studies in a RGP Contact Lens Polymer Paraperm by Positron Lifetime Technique

“…Based on these results, we tried to fit the experimental results using Eq. (8). It showed us that Eq.…”

“…The parameter A d depends mainly on the size of the diffusant while B d depends on the minimum volume required for the displacement of the diffusant. Since diffusion depends on the chemical structure of the polymer and the size of the diffusant molecules, understanding of the diffusion mechanism is usually done through the application of Fick's laws and its modified versions from which one can obtain information on the rate of diffusion and the polymer segmental relaxation [7,8].…”

Effect of cross‐linking on the free volume properties of natural rubber

“…The sorption isotherms showing mass-time curves are plotted in Fig. 1 for four different weight percents of sulphur indicated in the Figure. At the equilibrium mass values, the value of the network chain density was calculated for each sulfur concentration in the network via the modified Flory-Rehner equation [8,17].…”