Permeation of Mixed Penetrants through Glassy Polymer Membranes.
Final rept. Feb 81-Jan 85,
NORTH CAROLINA STATE UNIV AT RALEIGH
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This report summarizes the results of research activities supported by the Army Research Office. Three important areas were investigated 1 Selective permeation of mixed gaseous penetrants in glassy polymers 2 Transport of a reactive penetrant in polymers and 3 Effects of chemical modification resulted from exposure to reactive penetrants on the permeability of the polymer to permanent gases. The results of the first study indicated that the penetrants in a gaseous mixture compete with each other for diffusion paths provided by the microvoid sorption sites existing typically in a glassy polymer when the polymer was vitrified. The permeability to a given penetrant in a mixture is depressed from its pure-component value simply due to the competition effect. In the second area, we found that polyimide, often quoted for its chemical stability, is susceptible to attack by a strong nucleophile, ammonia. Finally, through ESCA and permeability measurements, we demonstrated that high-temperature fluorination of polyethylene, which gives a relatively well defined surface fluorinated layer, is controlled by the diffusion rate of fluorine. On the other hand, room temperature fluorination tends to be reaction-controlled and results in a distribution of fluorine atoms throughout the thickness of the film.
- Polymer Chemistry