Fluorinated ionomers properties

Heitner-Wirguin, C. Recent advances in per-fluorinated ionomer membranes structure, properties and applications. J. Membr. Sci. 1996, 120 (1), 1-33. 

Dependence of the membrane properties from membrane type (nonfluorinated and partially fluorinated ionomer). We have developed partially fluorinated covalently cross-linked membranes by reaction of disulfmated poly (ethersul-fones) with pentaflnorobenzene sulfochloride and different cross-hnkers [90]. The scheme for the preparation of such partially fluorinated covalent ionomer networks is given in Fig. 8.10. The obtained membranes showed high H -conductivities and moderate SW. In Table 8.5, some of the properties of one... 

Table 8.5 Properties of nonfluorinated and partially fluorinated ionomer membranes...

Tan, L., and Buskanin, R.S. Emulsion polymerization of fiuorinated monomers using per-fluorinated and/or ionomers as surfactant emulsifiers in the process, U.S. Patent 7,262,246 (August 28, 2007) to 3M Innovative Properties Co. 

One of these, which has recently become increasingly important in electrochemical applications, and which is one of the materials discussed extensively in this volume, is the Nafion ionomer family. These materials were developed by the duPont company, and consist of hydrophobic fluorocarbon backbone chains, with hydrophilic per-fluorinated ether side chains terminated by sulfonic acid groups or corresponding alkali salts. The Nafions possess many exceptional properties which are not encountered in other ionomer systems, particularly the high water permeability (26,27), permselectivity with regard to ion transport (28-30), durability in strong alkali (26), thermal stability (26,31), and others. 

There is no doubt that the perfluorinated ionomer membranes take initiative in this field and contribute a great deal in the commercialization and wide diffusion of fuel cells in the early stage. In terms of environmental compatibility (recyclability or disposability) and production cost, the perfluorinated ionomer membranes should be replaced with non-fluorinated alternative materials within the next decade. Challenge is how to achieve comparable conductivity and durability with the non-fluorinated membranes. Currently, no alternative materials have overcome the trade-off relationship between these two conflicting properties. In addition to the... 

Guiver et al. of National Research Council, Canada developed comb-shaped poly(arylene ether) electrolytes containing 2-A sulfonic acid groups on aromatic side chains (d) [76]. Their membranes showed relatively high proton conductivity and well-developed and continuous ionic domains. However, trade-off relationship between water uptake and proton conductivity of their membranes was not better than that of Nafion. In order to pronounce the hydrophilic/hydropho-bic differences, another series of comb-shaped aromatic ionomers with highly fluorinated main chains and flexible poly(a-methyl styrene sulfonic acid) side chains were developed [77]. The membranes seemed to have better properties than their previous version, however, chemical instability of the side chains needed to be improved. 

Figure 6-61. Heat-resistance properties of resins retaining 50 percent of properties obtainable at room temperature with resin exposure and testing at elevated temperature. Zone 1 Acrylics, cellulose esters, LDPE, PS, PVC, SAN, SBR, UF, etc. Zone 2 Acetals, ABS, chlorinated polyether, ethyl cellulose, EVA, ionomer, PA, PC, HDPE, PET, PP, PVC, PUR, etc. Zone 3 PCTFE, PVDF, etc. Zone 4 Alkyds, fluorinated ethylene-propylene, MF, polysulfone, etc. Zone 5 TS acrylic, DAP, epoxy, PF, TS polyester, PTFE, etc. Zone 6 Parylene, polybenzimidazole, silicone, etc. Zone 7 PAI, PI, etc. Zone 8 Plastics in R D etc. Since plastics compounding is rather extensive, certain basic resins can be modified to meet different heat-resistance properties.

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