Aciplex® membranes

Miyake, N. et ah. Durability of Asahi Kasei Aciplex membrane for PEM fuel cell application, in Proceedings of the 206th ECS Meeting Proton Conducting Membrane Fuel Cells IV, Honolulu, HI, October 3-8, 2004, p. 333. 

PFSA lonomer and PTFE Reinforcement at Asahi Kasei Aciplex Membranes.794... 

This chapter also presents a comparison between Nafion 112 and Aciplex 1002 membranes, showing almost indistinguishable performance in the lower current density region (Figure 27.51). At higher current density, the superior behavior of Aciplex was attributed to the lower EW of the Aciplex membranes [94]. 

FIGURE 27.49 V-I curve of Aciplex membranes. Cell performance was evaluated with a single cell of 10 cm electrode area. The Pt loadings of anode and cathode were about 0.1 and 0.2 mg cm , respectively. Source Asahi Kasei. (From Wakizoe, M., Kodani, T., and Ota, T., Abstracts of the 2003 Fuel Cell Seminar, 2003.)... 

Ferrous iron in the anolyte is oxidized to Fe " by dissolved chlorine. Since the solubility product of ferric hydroxide is very small ( 10 ), iron deposits on the membrane surface before it can penetrate the membrane. Iron, therefore, does not affect the selectivity of the membrane but may increase the voltage drop by reducing the effective area. Nickel has similar effects. Iron is generally less harmful because of very low solubility. However, it was reported [109] that in the presence of iron contamination, the current efficiency of Asahi Chemical cells with Aciplex membranes decreased by 2%. The cell voltage, on the other hand, was unaffected over 50 months of operation. The source of the iron was potassium ferrocyanide, an anticaking agent in the evaporated salt used as the raw material. 

Miyake, N., Wakizoe, M., Honda, E., and Ohta, T. 2006. High durability of Asahi Kasei Aciplex membrane. ECS Transactions 1 249-261. 

FIGURE 12.12 The comparison of single-cell performance between Nafion membrane and Aciplex membrane. (From Yi Baolian, Fuel Cell—Principal, Technology, Application[M], The Chemical Industrial Press, Beijing, China, 2003.)... 

The ML32NCH electrolyser equipped with the Aciplex F-4401 membrane has been in commercial operation at 6 kA m-2 for approximately one year at Asahi Chemical s chlor-alkali plant. As shown in Figs 17.16 and 17.17, the electrolyser has achieved a cell voltage of 3.17 V and a current efficiency of 96%, while operating at 6kA m-2. This operation is continuing the present plan is to investigate the performance of the ML32NCH at a current density of 8 kA m-2. 

Later, Hinatsu et al. studied the uptake of water, from the liquid and vapor states at various temperatures, in acid form Nafion 117 and 125, and Aciplex and Flemion membranes, although the latter two similar products will not be discussed here. These studies were motivated by a concern over the deleterious effects, involving either overly dry or overly wet membranes, on electrical conductivity within the context of polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. 

As discussed above, the most commonly known and studied PEMs are based on nonaromatic perfluori-nated hydrocarbons such as Nation, Aciplex, Flemion, and what are termed the Dow membranes. However, their chemical synthesis is challenging due to the safety concerns of tetrafluoroethylene and the cost/ availability of the perfluoroether comonomers. These issues have relegated detailed synthetic research on polyperfluorosulfonic acid materials to the industrial sector or to a few specialized academic labs. 

Other perfluorinated ionomer membranes, chemically very similar to Nafion, are also available commercially. Aciplex, manufactured by the Asahi Chemical Company, is very similar to Nafion, except that it has perfluoropropanesulfonic acid side chains. Flemion (Asahi Glass Company), in contrast, possesses perfluorobutanoic acid functions. 

The PFSA membranes nsed in the present study were Aciplex-SF-1004 with dimension of 10x10x0.117 tmn. The polymers were irradiated with 1.17 and 1.33 MeV garmna-ray from a cobalt-60 source, installed at the Takasaki Research Establishment of Japan Atomic Energy Agency (IAEA), at room temperatnre and atmospheric pressure. The resultant ionization doses to the polymers by the ganrma-ray irradiation were 530 kGy. 

PEMFCs generally operate at temperatures <100°C. PFSA-based polymer ionomer membranes like Nafion, Gore, Aciplex, and Flemion are not significantly affected by temperatures up to 150°C where most of the water is lost and membranes may suffer irreversible dry out. Chemical degradation of these membranes in the form usually starts with the loss of sulfonate groups at over 220°C [7]. 

The synthesis of the monomers as well as the polymerization of PFSA membranes involve dangerous reactions under conditions of high pressure and temperature. Additionally, the synthesis of the comonomer that is commonly referred to as perfluorosulfonylfluoride ethyl propyl vinyl ether (PSEPVE) involves numerous steps with low yields. These factors contribute to the cost of these materials. The synthesis routes described in detail by Doyle and Rajendran are summarized here. The synthesis of the long-chain PFSA monomers used in commercial systems like Nafion, Flemion, and Aciplex proceeds through... 

Asahi Kasei develops membranes mainly for chlor-alkali electrolysis technology with Aciplex F PFSA membranes. The Aciplex F membrane is employed in plants with a total production capacity of over 5 million tons of sodium hydroxide... 

FIGURE 27.51 Performance comparison between fuel cells with Nafion 112 and Aciplex 1002 membranes according to Du et al. (Reproduced from Du, X.Z., Yu, J.R., Yi, B.L., Han, M., and Bi, K.W., Phys. Chem. Chem. Phys., 3, 3175, 2001. With permission from the PCCP Owner Societies.)... 

Despite perfluorinated polymer electrolytes (Nafion, Flemion, Aciplex) having been used extensively in PEMFCs, their poor thermal mechanical stability (low Tg), high methanol permeability, and extremely high production costs have led to limitations of their large-scale application. Therefore, a variety of hydrocarbon polymer electrolytes have been developed during the past decade, with the greatest emphasis placed on the costs, conductivity, and durability of these materials. At the same time, the poor mechanical stability and inadequate durability of the hydrocarbon polymer membranes were identified as the main barriers to their practical application. 

T. Hanaoka, R. Tanaka, M. Tasaka, M. Hamada and K. Yoshie, Thermal membrane potential across test anion-exchange membrane Aciplex STA and the transported entropy of counterions, Maku (Membr.), 1993,18, 363-370. 

MAJOR APPLICATIONS Nafion is the DuPont trademark for its family of perfluorinated ionomers, that is, resins and membranes. Asahi Chemical Industry Company produces Aciplex and Asahi Glass Company, Ltd., Japan, produces Flemion both are competitive products to Nafion in form and function. These perfluorinated ionomers are used in a variety of applications, the largest of which are as an ion exchange resin and in membrane separators in the commercial electrolysis of brine to produce caustic and chlorine. Nafion membranes are also being used in the development of fuel cells and as heterogeneous super acid catalysts in supported, cubed, or powdered form. 

Perfluorosulfonic acid (PFSA) membranes as shown in Fig. 1 were first developed for fuel cells by DuPont as Naflon and installed into the Biosatellite spacecraft in 1967 [1,2]. Various types of PFSA polymers, such as Flemion , Aciplex , and Dow membrane, were developed subsequently. They have excellent chemical stability, high proton conductivity, and high water diffusivity in a wide range of temperatures, brought about by the nature of fluorinated compounds and these non-cross-linked structures [3-5]. 

The molecular structure of a conventional polymer used for a PFSA membrane is shown in Fig. 1. Membranes registered as Nafion (DuPont), Flemion , (Asahi Glass), and Aciplex (Asahi Chemical) have been commercialized for brine electrolysis and they are used in the form of alkali metal salt. Figure 4 shows a schematic illustration of a membrane for chlor-alkali electrolysis. The PFSA layer is laminated with a thin perfluorocarboxylic acid layer, and both sides of the composite membrane are hydrophilized to avoid the sticking of evolved hydrogen and chlorine. The membrane is reinforced with PTFE cloth. The technology was applied to PEFC membranes with thickness of over 50 xm [14]. 

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