Sulfonated polyether ketone

Several reviews on membranes for DMFC fuel cells have been published in the last decade [1-9], starting with that by Kreuer [1], discussing the differences between Nafion and sulfonated polyether ketone membranes. According to Fig. 6.1, reviews published till 2006 [1 ] cover only one third of the ionomeric membranes currently developed for DAFC. More recent reviews deal with polyimide ionomer membranes [5], composite membranes for high temperature DMFC [6], non-perfluorated sulfonic acid membranes [7], modified Nafion membranes [8], and hybrid membranes [9-11]. 

One of the significant differences between hydrocarbon ionomers and perfluoro-sulfonic acid polymers is add groups. The pKa value of benzenesulfonic acid (PhSOsH) is 2.5 and that of trifluoromethanesulfonic acid (CF3SO3H) is —13. The pKa value was estimated to be ca. 1 for sulfonated polyether ketone and ca. —6 for Nafion membranes [78]. Therefore, the effective proton concentration and proton mobility should be lower in the hydrocarbon ionomer membranes. Without appropriate molecular design such as multiblock copolymer and sulfonic acid clusters as mentioned above, hydrocarbon ionomer membranes lack well-developed ionic channels due to less pronounced hydrophilic and hydrophobic phase separation, which causes the lower proton conductivity at low humidity. 

New organic-inorganic composite membranes based on sulfonated polyether-ketone (SPEK) and SPEEK were synthesized with SiO, TiO, and ZrO. The modification of SPEK and SPEEK with ZrO reduced the methanol flux by 60-fold. On the other hand, there was a big compromise on conductivity, which was reduced by 13-fold, while modification of PEK and SPEEK with silane (SiO ) led to a 40-fold decrease of water permeability without a large decrease of protonic conductivity [35]. With some encouraging results of the modification of PEK with SiO, TiOj, and ZrO, modification of PEK with heteropolyacid further yielded some notable results. Actually the composite membranes were prepared using an organic matrix... 

Sulfonated polyether ketones are obtained by reaction with chlorosulfonic acid and have potential as asymmetric membranes. Under suitable conditions, the polymer chain was not degraded, although chlorosulfonated derivatives were not isolated. ... 

High performance resins Polyphenylene sulfide Polysulfone Polyether sulfone Polyether ketone Polyether ether ketone Polyetherimide... 

The swelling in liquid water could be a nonrelevant value to describe the membrane behavior in fuel cells. As an example, the sulfonated polyether ketones suffer from an excessive water uptake when immersed in hquid water at elevated temperatures [110], while a high-temperature fuel eeU test over 1400 h has been performed with fully hydrated gases [2]. Therefore, the swelling in hquid water at elevated temperature is of limited value. Most of the authors prefer nowadays to determine the water uptake under defined temperature and RH conditions. Water sorption isotherms have been measured and analyzed [40,104,119]. These results confirmed the previous data since the sorption isotherms are superimposable when expressed in 2 values for different ion contents and chemical structures [40,48,49,56]. The sorption isotherms were classically analyzed as the superposition of different phenomena (Henry, clustering, dual-mode, Flory-Huggins, and BET II processes) [119]. The water sorption isotherms exhibit a distinct sorption-desorption hysteresis, which was attributed to the very low desorption process [40]. 

Polyarylether Ketones. The aromatic polyether ketones are tme thermoplastics. Although several are commercially available, two resins in particular, poly ether ether ketone [31694-16-3] (PEEK) from ICI and poly ether ketone ketone (PEKK) from Du Pont, have received most of the attention. PEEK was first synthesized in 1981 (20) and has been well studied it is the subject of numerous papers because of its potential use in high performance aircraft. Tough, semicrystalline PEEK is prepared by the condensation of bis(4-fiuorophenyl) ketone with the potassium salt of bis(4-hydroxyphenyl) ketone in a diaryl sulfone solvent, such as diphenyl sulfone. The choice of solvent is critical other solvents, such as Hquid HE, promote the reaction but lead to premature low molecular-weight crystals, which do not exhibit sufficient toughness (21). 

In addition to Nafion-based catalyst layers, additional types have been developed, including CLs with different ion exchange capacities (lECs) [57,58] or with other hydrocarbon-type ionomers such as sulfonated poly(ether ether ketone) [58-60], sulfonated polysulfone [61,62], sulfonated polyether ionomers [63], and borosiloxane electrolytes [64], as well as sulfonated polyimide [65]. These nonfluorinated polymer materials have been targeted to reduce cost and/or increase operating temperature. Unfortunately, such CLs still encounter problems with low Pt utilization, flooding, and inferior performance compared wifh convenfional Nafion-based CLs. 

Various kinds of engineering thermoplastics such as polyether sulfone, polyether imide, polyaryl ether ketone, and polyphenylene oxide have been studied as toughening agents for... 

There are also a few common polymers whose accepted names convey relatively little information about the repeating unit structure. The primary examples are polycarbonate, poly(phenylene oxide), polyamide-imides, poly-sulfones, and polyether ketones (see Table 1.3). 

PTFE can be compounded with polymeric fdlers with adequate thermal stability. Examples of such polymers include polyarylates such as polyether-ketone, polyphenylene sulfone, and polyphenylene sulfide. Surface characteristics such as wear rate, coefficient of friction, and surface tension can be modified with these additives. 

To prepare new and inexpensive membranes, various trials have been made 196 sulfonated aromatic polyether membrane such as polyether ketones (PEEK),197 sulfonated polysulfone198 and membranes from sulfonated polyphenylene sulfide,199 phosphoric acid-doped polybenzimidazole, (PBI),200 polybenzimidazole having sulfonic acid groups,201 polybenzimidazole with phosphonic acid groups,202 a blend membrane of polybenzimidazole and sulfonated polysulfone,203 sulfonated phosphazene polymer.204... 

X = CO Phenolphthalein polyether-ketone (PEK-C) X = SO2 Phenolphthalein polyether-sulfone (PES-C)... 

Fra Francis, B., Thomas, S., Thomas, S. P., Ramaswamy, R., Rao, V. L. Diglycidyl ether of bisphe-nol-A epoxy resin-polyether sulfone/polyether sulfone ether ketone blends phase morphology, fracture toughness and thermo-mechanical properties. Colloid Polym. Sci. 285 (2006) 83-93. 

Ismail AF, Othman NH, Mustafa A (2009) Sulfonated polyether ether ketone composite membrane using tungstosilic acid supported on silica-aluminium oxide for direct methanol fuel cell (DMFC). J Membr Sci 329 18-29... 

Mecheri B, D Epifanio A, Traversa E, Licoccia S (2008) Sulfonated polyether ether ketone and hydrated tin oxide proton conducting composites for direct methanol fuel cell applications. J Power Sources 178 554-560... 

Shan J, Vaivars G, Luo HZ, Mohamed R, Linkov V. Sulfonated polyether ether ketone (PEEK-WC)/phosphotungstic acid composite ... 

Polyether ketone ketone Polyether sulfone or polysulfone Polyethylene... 

Figure 7.10 Schematic representation of the possible interactions between the sulfonated polyether-ether ketone and the titanium-based component in the hybrid matrix.

Figure 7.16 Water uptake in sulfonated polyether-ether ketone (SPEEK) +Ti02 nanocomposite membranes as a function of the filler content. 0 refers to the untreated T1O2,1 to the dopamine-treated Ti02, and 2 to the polyethylene-imine-treated T1O2.

Zhou et al. [173] studied the effects of surface treatment of calcium carbonate particles with sulfonated polyether ether ketone on the mechanical and thermal properties of composites with polyether ether ketone in various proportions prepared using a twin-screw extruder. These workers used tensile, impact, and flexural testing, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The influences of filler particle, loading, and surface treatment on deformation and crystallinity of polyether ether ketone were discussed. 

In a cost comparison by Gebert et al. [42], it is concluded that sulfonated Polyether ether ketone (S-PEEK) and phosphoric acid-doped polybenzimidazole (H3PO4-PBI) could be a factor of five cheaper than Nafion. As discussed earlier, this cost advantage is only helpful when not offset by lower MEA power density. 

PE professional engineer PECTFE Polyethylene chlorotrifluoroethylene PEEK polyetheretherketone PEEL polyether ester PEI polyetherimide PEK polyether ketone PEKK polyether ketone ketone PEN polyethylene naphthalate PES polyether sulfone PET polyethylene terephthalate PETG polyethylene terephthalate glycol... 

High performance engineering thermoplastics have recently assumed increasing importance due to their exceptional properties at elevated temperatures. A number of such specialty polymers have been introduced into the market for high temperature applications and examples of some of the outstanding ones are polyphenylene oxide (PPO), polyphenylene sulfide (PPS), polyether sulfone (PES), polyaryl sulfone (PAS), polyether ketone (PEEK), polyether imide (PEI) and polyarylate (PAr). 

It has been suggested that instead of membranes made from perfluorinated sulfonic acids (PFSAs), membranes be used made from other, heat-resistant polymers containing the sulfonic acid group. One could think here of sulfonated polyimides (SPIs) and sulfonated polyether ether ketones (SPEEKs). Membranes made from such polymers have a sufficiently high protonic conductivity at elevated temperatures but are less sensitive to lower humidities and water loss. 

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