Determining Extent of Ion-Exchange in Various Counterion Nafion Membranes Using Prompt Gamma Neutron Activation Analysis (PGAA)

Report No. ARL-TR-2679
Authors: Sandra K. Young, Samuel F. Trevino, Nora C. Beck Tan, and Rick L. Paul
Date/Pages: March 2002; 28 pages
Abstract: 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.
Distribution: Approved for public release
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Last Update / Reviewed: March 1, 2002