Perfluorocarboxylate membranes Flemion

A novel perfluorocarboxylate membrane named Flemion was developed by Asahi Glass Co., Ltd. in 1975, resulting from its long experience both with manufacture of various fluorochemicals and with electrodialysis using membranes. 

This chapter summarizes the preparation and the fabrication of perfluorocarboxylate polymers and their fundamental properties including those of the ionized salt-type membranes. The application of Flemion in chlor-alkali electrolysis is also described. 

Perfluorocarboxylate ionomer Flemion Asahi Glass Chloralkali membrane... 

The Nafion membranes have ionic contents of 0.66-0.91 Eq/kg. A bUayer of these two extremes of composition is made and also a bilayer with a perfluorocarboxylate (Flemion) polymer. The bilayered membranes are made by melt processing the precursor copolymer, which then, in membrane form, is hydrolyzed. 

The molecular structure of a conventional polymer used for a PFSA membrane is shown in Fig. 1. Membranes registered as Nafion (DuPont), Flemion , (Asahi Glass), and Aciplex (Asahi Chemical) have been commercialized for brine electrolysis and they are used in the form of alkali metal salt. Figure 4 shows a schematic illustration of a membrane for chlor-alkali electrolysis. The PFSA layer is laminated with a thin perfluorocarboxylic acid layer, and both sides of the composite membrane are hydrophilized to avoid the sticking of evolved hydrogen and chlorine. The membrane is reinforced with PTFE cloth. The technology was applied to PEFC membranes with thickness of over 50 xm [14]. 

Perfluorocarboxylates, the Flemions, were introduced with the idea that a carboxylate at a given ion content would be less hydrophilic than a sulfonate and so would be of help in balancing the ionic content of an ion-exchange membrane with its permselectivity and hydrophilicity as required. The bilayered Nafions also resulted from similar thinking and at tempt to combine certain advantages of the two types. 

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