Fluorinated ionomers

W. Grot, Fluorinated ionomers, PDL handbook series, William Andrew Pub., Norwich, N.Y., 2008. 

The experimental collection efficiencies for H202 (estimated Graham s law diffusion coefficient is 0.18 cm2/s) for an aqueous scrubber Nafion (per-fluorinated ionomer) membrane DS (L = 40 cm, d0 = 0.5 cm, and d = 0.06 cm) have been experimentally determined by two independent ap-... 

Major areas of application are in the field of aqueous electrochemistry. The most important application for perfluorinated ionomers is as a membrane separator in chloralkali cells.86 They are also used in reclamation of heavy metals from plant effluents and in regeneration of the streams in the plating and metals industry.85 The resins containing sulfonic acid groups have been used as powerful acid catalysts.87 Perfluorinated ionomers are widely used in worldwide development efforts in the held of fuel cells mainly for automotive applications as PEFC (polymer electrolyte fuel cells).88-93 The subject of fluorinated ionomers is discussed in much more detail in Reference 85. 

Nation and other fluorinated ionomers are copolymers of tetrafluorethylene (TFE) and perfhiorinated vinyl ethers... 

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

The first two books of the series cover commercial fluoropolymers (ethylinic) the third book focuses on their applications in the chemical processing industries. The fourth book deals with fluoroelastomers, the fifth with fluorinated coatings and finishes, and the sixth book is about fluorinated ionomers such as Nafion . 

The use of low-cost basic polymers instead of Nation is an interesting alternative [19,20].The development of new polymers for ionomer membranes including perfluorinated ionomers, partially fluorinated ionomers, nonfluorinated ionomers, high-molecular/low-molecular composite membranes as well as novel polymer modification processes and novel membrane materials is summarised in [21]. 

K.A. Mauritz, Organic-inorganic hybrid materials Per-fluorinated ionomers as sol-gel polymerization templates for inorganic alkoxides. Materials Science and Engineering C—Biomimetic and Supramolecular Systems 1998, 6, 121-133. 

Gore-Select membrane is a recent innovation that is useful for fuel cells. The membrane is made by filling the pores of Gore-Tex (expanded PTFE) with a per-fluorinated ionomer Hke Nafion. The resulting membrane is about 20 pm thick, about one tenth the thickness of a Nafion membrane, and it has about half the resistance of Nafion. Membrane-electrode assembhes are made by applying platinum black coatings (0.3 mg/cm ) to both surfaces. They are reported to perform well in fuel cells [46]. 

M. Saito, S. Tsuzuki, K. Hayamizu, T. Okada, Alcohol and proton transport in per-fluorinated ionomer membranes for fuel cells, J. Phys. Chem. B 110 (2006) 24410-24417. 

Industrial availability of ionomeric dispersion is today limited to fluorinated ionomers one. 

Fluorinated ionomers are known for their use as ion-permeable electrolyte membranes most commonly in chloro-alkali electrolysis, electrochemical devices, and H2/O2 fuel cells. The polymer membrane facilitates the transport of protons between... 

From the reviewed work, it can be concluded that obviously the use of partially fluorinated aromatic cationomers as ionical cross-linkers leads in most cases to better chemical and thermal stabilities of the blend membranes than if nonfluorinated cationomers would be applied as acidic blend components. Among aU acidic cross-linkers, the sulfonated and partially fluorinated ionomer S9 (Fig. 4.5) leads to the best chemical stability of the referring base-excess PBI blend membranes. 

Yandrasits M (2011). New fluorinated ionomers for proton exchange membranes . In Advances in New Materials for Proton Electrolyte Fuel Cell Sjvife/Mi, Asilomar, CA. 

Partially fluorinated ionomer membranes Among this material class is the BAM3G membrane type composed of sulfonated or phosphonated poly(a,(5,(5-trifluorostyrene) and its copolymers [2-4] and the different types of grafted membranes based on partially fluorinated polymer foils, as developed by Scherer [5], Sundholm [6], and others. 

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...

Research has been actively conducted for the past 20 years in search of alternatives to perfluorinated membranes for PEMFC and DMFC applications. Partially fluorinated ionomers are of great interest among other various candidates in such efforts. Like perfluorinated membranes, partially fluorinated ionomers also have a PTFE-like polymer backbone as a main part to resist chemical attacks. However, ionic groups are attached to styrenic moieties instead of perfluorinated side chains. Due to its availability and easy sulfonation, styrene is a reasonable choice for ionomeric materials. In the late 1990s, Ballard Power Systems introduced a partially fluorinated low-cost membrane for fuel cell applications [24,47,48]. Ballard Advanced Materials (BAM) membrane is a family of sulfonated styrenic co-polymers of a,p,p-trifluorostyrene and substituted a,p,p-trifluorostyrene co-monomers by emulsion polymerization. The chemical structure of BAM membrane is shown in Fig. 13.9. 

Althongh perfluorinated or partially fluorinated ionomers are mostly favored as fuel cell membrane materials due to their unique resistance to chemical attack from their surroundings, fundamental solution to overcome inherent shortcomings of Nafion and other fluorinated membranes would be the development of chemically different types of ionomers. Alternative membranes for PFS A can reduce methanol crossover as low as two orders of magnitude. Such membranes are discussed in the following sections. 

New electrolyte formulation Non-fluorinated ionomer membranes such as phosphazene, arylene, poly(benzimidazole) or FBI, hydrocarbon polymers, nanoporous silicon membranes to serve as proton conductors (Apanel et al., 2(X)4 Chu et al., 2(X)5). 

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