Actions for MOLECULAR DIFFUSION IN CONCENTRATED POLYMER SOLUTIONS (FREE-VOLUME THEORY, DEBORAH NUMBER, THERMAL HISTORY).

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MOLECULAR DIFFUSION IN CONCENTRATED POLYMER SOLUTIONS (FREE-VOLUME THEORY, DEBORAH NUMBER, THERMAL HISTORY).

Author
HOU, AN-CHI
Physical Description
102 pages
Additional Creators
Pennsylvania State University
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Summary
The free volume theory for diffusion in concentrated polymer solutions proposed by Vrentas and Duda is evaluated using diffusivity data collected over wide temperature and concentration ranges for the toluene-poly(vinyl acetate) system. The conventional sorption technique is utilized to measure the mutual diffusion coefficients.
The influence of solvent shape on the diffusion is investigated. The Vrentas-Duda free volume theory is used to interpret the diffusion mechanism of such irregular shape molecules in polymer solutions. It is found that the segmentwise diffusion occurs for n-alkane molecules with sufficient length in molten polystyrene. This result is compared with the diffusion rate of other solvents of similar size but with spherical shape.
The predictive capabilities of Vrentas-Duda, Fujita, and Paul versions of free volume theory are examined. The expressions for concentration dependence of mutual diffusion coefficients at the pure polymer limit are derived for each version. Experimental data are compared with predictions of these three versions of free volume theory.
Anomalous diffusion is observed in ethylbenzene-poly(ethyl methacrylate) system at 120(DEGREES)C, which is more than 50(DEGREES)C above the glass transition temperature of the polymer. The diffusion Deborah number, which indicates the relative rates of the diffusion of penetrant molecules and the relaxation of polymer molecules to new conformations, is calculated. The Deborah number criterion is then evaluated by experimental findings.
Diffusion of organic solvents in glassy polymers is investigated. The influence of thermal treatment for polymers on the diffusion coefficients is also examined and interpreted with free volume concept. Diffusivity data above glass transition temperature are used to predict the diffusion coefficients below glass transition temperature by the Vrentas-Duda free volume theory.
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Dissertation Note
Ph.D. The Pennsylvania State University 1986.
Note
Source: Dissertation Abstracts International, Volume: 47-07, Section: B, page: 3018.
Part Of
Dissertation Abstracts International
47-07B
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