Nafion/poly(vinyl alcohol) blends: Effects of crosslinking conditions on transport properties
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Optimizing the efficiency of the direct methanol fuel cell requires new polymer electrolyte membranes (PEM) that exhibit high selectivity (i.e., high proton conductivity and low methanol crossover). Crosslinked polymer blend membranes of Nafion and poly(vinyl alcohol) (PVA) were developed and studied. Crosslinked PVA had a higher affinity for water compared to methanol, where Nafions preference is reversed. Blend membranes were crosslinked both chemically and thermally, where thermal crosslinking was performed at 120-250C. Proton conductivity decreased with increasing PVA content in the blend; however these trends differed based on the crosslinking technique. More specifically, at low PVA contents and high crosslinking temperatures, blend membranes were two times more selective with a similar proton conductivity compared to Nafion 117 the most commonly used PEM in fuel cells. Blend membranes showed a reverse trend with increasing crosslinking temperature, where proton conductivity remains constant, while methanol crossover decreases. This is an abstract of a paper presented at the AIChE Annual Meeting and Fall Showcase (Cincinnati, OH 10/30/2005-11/4/2005).
