Proton exchange membranes by radiation grafting of styrene onto FEP films. IV. Evaluation of the states of water

✍ Scribed by Bhuvanesh Gupta; Otto Haas; Günther G. Scherer

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 581 KB
• Volume: 57
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1995.070570709

✦ Synopsis

The nature of water in proton exchange membranes, obtained by radiation grafting of styrene onto poly(tetrafluoroethy1ene-co-hexafluoropropylene) (FEP) films and subsequent sulfonation, was investigated by differential scanning calorimetry. It was found that the membranes contained three different types of water, which were categorized as freezingfree, freezing-bound, and nonfreezing water. The degree of grafting had a considerable influence on the relative ratios of these three types of water molecules. The nonfreezing water per ion-exchange site ratio was found to be independent of the degree of grafting. However, freezing-free and freezing-bound water per ionic site ratios increased with increasing graft levels. A correlation between the water uptake and the structural changes occurring in the membrane as a function of the degree of grafting was established. 0 1995