Perfluorinated ionomer membranes permselectivity

Perfluorinated ionomer membranes show considerable promise with respect to their performance characteristics, low resistivity, high permselectivity, and long-term stability. However, the present cost of these membranes is more than 300 per square meter. The relatively high cost limits their application in many electrochemical cells when cost effectiveness is a major concern. 

The most important commercial application of perfluorinated ionomer membranes is currently in the chlor-alkali industry. These materials are used as permselective separators in brine electrolysis cells for the production of chlorine and sodium hydroxide. This... 

H. L. Yeager and J. D. Mallnsky, "Permselectivity and Conductance of Perfluorinated Ionomer Membranes 1n Chlor-Alkali Electrolysis Process", presented at the Amer. Chem. Soc. Mtg., Philadelphia, Aug. 1984. 

Perfluorinated ionomer membranes have been developed for use as separators in chlor-alkali electrolysis cells. Using an automated test apparatus, the current efficiency and voltage drop of such a high performance membrane were evaluated as a function of several cell parameters. Results are plotted as three dimensional surfaces, and are discussed in terms of current theories of membrane permselectivity. 

For isolation of electrode reactants in either an energy storage cell or an electrochemical cell employed for electrosynthesis, a chemically and physically stable, permselective separator membrane is generally required. Two recent classes of polymeric materials are of interest for such application perfluorinated ionomers of which Nafion[48,49] is an example, and alkali metal-coordinating polyethers and polyesters of which polyethylene oxide-LiCFaSOa mixture is an example[50-52]. 

This is evidenced by the amount of literature on ionomers and by the appearance of two monographs devoted to the subject (J, ). Most of the research effort on the ionomers has focused on only a small number of materials, notably ethylenes (3-9 ), styrenes (10,11), rubbers (12-16) and recently aromatic (17) and fluorocarbon-based ionomers (18). The last material is known for its high water permeability and cation permselectivity. Because of its unique properties, it has been employed as an ion-exchange membrane in chlor-alkali cell operations in electrochemical industries. Perfluorinated ion-exchange membranes are the subject of the present chapter. 

---