Predicting ability of free-volume theory for solvent self-diffusion coefficients in rubbers
โ Scribed by Seong-Uk Hong
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 622 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0021-8995
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โฆ Synopsis
The effect of solvent size on the diffusion process is studied for various solvents with natural rubber and polybutadiene in terms of the free-volume theory. The importance of energy effects on the diffusion of penetrants in rubbers is examined. The critical molar volume of the polymer jumping unit is correlated with its glass transition temperature over the range 172 K to 305 K. The correlation shows a linear relationship between these two properties and can be used to predict one of the most sensitive free-volume parameters. Using this parameter in conjunction with the Vrentas-Duda free-volume theory, solvent self-diffusion coefficients in rubbers are then predicted over wide ranges of concentration and temperature. For all the systems, the predictions are comparable with experimental data.
๐ SIMILAR VOLUMES
Several versions of free-volume theory have been proposed to correlate or predict the solvent diffusion coefficient of a polymer/solvent system. The quantity of free volume is usually determined by the Williams-Landel-Ferry (WLF) equation from viscosity data of the pure component in these theories.
It is well established that diffusion and relaxation processes in polymers above T, are closely related in that they are both governed by the polymer segmental motions, which are believed to be determined by the free volume present in the system. The diffusion coefficients of gases in elastomers can