Determining Extent of Ion-Exchange in Various Counterion Nafion Membranes Using Prompt Gamma Neutron Activation Analysis (PGAA)
Final rept. Jun 1999-Mar 2001
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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Researchers have performed structural evaluations on Nafion membranes for many years. Various research groups have published a large volume of data however, much of the work done by these groups is contradictory. One important aspect of the membranes is the chemical uniformity and quantity of water within the membrane under investigation. A new technique that has shown its usefulness for providing accurate and fast quantitative measurements of chemical composition quickly is prompt gamma neutron activation analysis PGAA. In this work, a sulfonyl fluoride-form membrane, an as-received membrane from the manufacturer, and several differently pretreated H-form Nafion membranes were examined using PGAA. The evaluation showed the necessity for pretreatment of membranes to eliminate contamination. A series of counterion-exchanged membranes were also examined to determine maximum conversion achieved and to identify possible limitations to complete conversion. The results show that it is possible to obtain nearly complete or complete conversion to the counterion from the H-form Nafion samples. Water content can be limited within the membrane but not eliminated. In samples that were not pretreated, complete ion exchange was limited by the contamination.
- Organic Chemistry
- Physical Chemistry