Nafion

2-[1-[Difluor[(trifluorethenyl)oxy]methyl]-1,2,2,2-tetrafluorethoxy]-1,1,2,2-tetrafluorethansulfonsäure

Ionomer

Stiff, white, odorless substance

Fixed

2.1 g/cm3

About 110 ° C ( in the dry state )

0.5 to 2.31 · 10-3 (m · ohm ) -1

Attention

Nafion is a sulfonated tetrafluoroethylene polymer ( PTFE), which was in charge of developing in the late 1960s by Walther Grot as a modification of Teflon. Nafion is an entirely new class of polymers known as ionomers. " Nafion " is a registered trademark of DuPont.

Properties

The addition of strongly acidic sulfonic acid Nafion was the first time a polymer with ionic properties. It shows some fundamentally different from those of the Teflon different characteristics while maintaining high chemical resistance:

• Rapid diffusion of water and alcohols, but hydraulically sealed
• Selectively conductive to protons and other cations ( barrier effect for anions)
• High operating temperatures as compared to other polymers (up to 190 ° C)

Technical applications for Nafion membranes

• Ion -exchange membranes in chlor -alkali electrolysis
• Drying or humidification of gases because of its high selectivity and permeability of water (vapor )
• Proton- exchange membrane for polymer electrolyte fuel cells
• Proton exchange membrane for direct methanol fuel cells
• Preparation of chromic acid and regeneration of verunreingten chrome baths
• Production of Kaliumdicyanidoaurat (-I ) by dissolution of a gold anode in potassium cyanide ( KCN)
• As a strongly acidic solid catalyst

A disadvantage in the industrial application of Nafion membranes for fuel cells, the degree of loss of proton conductivity above 100 ° C, too high a permeability of water and methanol for use in direct methanol fuel cells. However, this applies also for other perfluorinated exchanger materials.