Perfluorocarboxylic acid membrane preparation

Water Content. Figure 4 shows the relation between the water content of perfluorocarboxylic acid membrane prepared by chemical treatment and the ion exchange capacity with varying external solution concentration. As the concentration of the external solution increases, the membrane shrinkage increases and the water content is therefore decreased. The influence of... 

Figure 9. Electric resistance, ion exchange capacity (meq/g dry resin) and concentration of NaOH, for perfluorocarboxylic acid membrane prepared by chemical...

Table III shows the mechanical properties of perfluorocarboxylic acid membrane prepared by chemical treatment and perfluorosulfonic acid membrane.

Perfluorocarboxylic acid membrane prepared by chemical treatment... 

The monolayer perfluorocarboxylic acid membrane can be prepared, if necessary, by chemical treatment which causes the chemical reaction throughout the membrane. 

Figure 2. The thickness of CO OH layer, current efficiency, and electric resistance of a multilayer perfluorocarboxylic and sulfonic acid membrane prepared by chemical treatment (COOH/SOsH).

Perfluorocarboxylic acid membrane is prepared by hydrolyzing the film of copolymer of PVEX monomer with carboxylic acid group or its precursor and TFE by conventional method. 

The typical perfluorocarboxylic acid membrane developed by Asahi Chemical is a multilayer membrane prepared by chemical treatment. The structure of the membrane is optimized for high current efficiency and low electric resistance. The thickness of the carboxylic acid layer is in the range of 2 to 10 microns. The chemical structure of the membrane is as follows (72). 

Figure 1 shows the general methods for preparation of perfluorocarboxylic acid monolayer and multilayer membranes. 

Multilayer membranes with perfluorocarboxylic and per-fluorosulfonic acid groups can be prepared by lamination of two different films containing the respective polymers96 98 or by chemical conversion of perfluorosulfonic acid to perfluorocarboxylic acid.99"102 The latter method is preferred to achieve the desired thickness of 5-10 /xm of the carboxylic acid pendant group. 

These composite membranes are prepared either by lamination of the perfluoro-carboxylate and perfluorosulfonate films [75-77] or by the chemical conversion [78-80] of one surface of the perfluorosulfonic acid to perfluorocarboxylic acid to realize a carboxylate layer thickness of 5-10 xm. 

Terpolymerization (2, 3, 4, 6, 8, 33). Membranes containing both perfluorocarboxylic and sulfonic acid groups can be prepared by hydrolyzing a film formed by terpolymerization of TFE and two PVEX monomers containing a carboxylic ester group and sulfonyl fluoride group. 

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