Membrane durability

D. L. Peet, Membrane Durability in Chlor—Alkali Plants, Electrochemical Society Meeting, Honolulu, Hawaii, Oct. 1987 Proceedings of the Symposium on Electrochemical Engineering in the Chlor—Alkali and Chlorine Industries, PV. 88-2, 1988, pp. 329—336. 

All these parameters influence the durability of the membrane. Durability also depends on the area of application. 

Liu, W., Ruth, K. and Rusch, G. 2001. Membrane durability in PEM fuel cells. Journal of New Materials for Electrochemical Systems 4 227-232. 

Adverse oxidation of membrane occurs at higher concentrations of oxidizers such as chlorine, ozone and hydrogen peroxide. The chemicals are important for slime control, and rather high concentrations of the chemicals are dosed for sterilization of RO feed system, especially in cases of ultrapure water system, and of waste water treatment system. The evaluation of membrane durability against oxidizing chemicals informs us the proper procedures for RO maintenance. 

X. Huang, X. Wang, J. Preston, L. Bonville, H.R. Kunz, M. Perry, D. Condit, effect of water management schemes on the membrane durability in PEMFCs. ECS Trans. 16, 1697 (2008)... 

Liu, W. and Crum, M., Effective testing matrix for studying membrane durability in PEM fuel cells. Part 1. Chemical durability, ECS Trans., 3, 531, 2006. 

There are four principle causes for membrane failure under normal operating conditions (in other words, reduced membrane durability). These reasons are (a) hydrogen-induced embrittlement of the membrane, (b) fatigue fracture due to repetitive swelling and contraction of the membrane, (c) mismatch in the CTE of the membrane and underlying support layer, and (d) defects in the underlying support layer that cause a hole or tear to develop in the membrane. 

Figure 8.10. Apparatus for testing membrane durability with respect to hydrogen-induced swelhng.

When considering the influence of thermal expansion or hydrogen-induced expansion on membrane durability, it should be remembered that the absolute magnitude of expansion is dependent on the size (dimensions) of the membrane. Generally, smaller membranes will be more durable than larger membranes. 

Very little is known about the influence of grain growth, or crystallization if the membrane is composed of an amorphous alloy, on membrane durability. The as-fabricated permselective metal membrane will be polycrystalline or amorphous, depending on the alloy composition and fabrication method. Amorphous, or metallic glass, structures are far less common than are polycrystalline structures. Both amorphous and polycrystalline structures are quasi-stable, meaning that structures are kinetically stabilized and slow to rearrange to the thermodynamically favored structure. In both cases, this would be a single crystal of the metal. 

Gode, P. Ihonen, J. Strandroth, A. Ericson, H. Lindbergh, G. Paronen, M. Sundholm, F. Sundhohm, G. Walsby, N. Membrane durability in a PEM fuel cell studied using PVDF based radiation grafted membranes. Fuel Cells 2003, 3 (1-2), 21-27. 

Specifically, the limitations of greatest practical significance are the following (1) low permeation flux, (2) inadequate permselectivity, (3) inadequate membrane durability or service lifetime, (4) membrane fouling, and (5) excessively high capital or operating costs. These deficiencies render LM processes either technically impractical or (more often) uneconomic, for such apphcations. 

Ways to increase membrane durability have been examined by various researchers across the country. Maurtiz et al. examined the use of metal-oxide metal particles to increase the properties of the membrane. A titanium isopropoxide (Figure 11.4) addition to Nation membranes generates quasi-network particles this improves membrane modulus and dimensional stability [17], In addition, the titanium matrix reduces fuel crossover and minimizes chemical degradation. Table 11.2 shows the increase in modulus along with stress and strain and stress changes after the addition of the titanium matrix [17], With a 20% load of the titanium matrix, performance criteria remain comparable. Acid functionality remains intact however, water uptake is reduced as volume inside clusters is occupied. Conductivity is reduced due to chain mobility [17],... 

Improved Cathodes High-Temperature Membranes Durability Studies Fuels Effects... 

Determine reformate effect on proton exchange membrane durability... 

The tube-and-shell, or tubular, membrane module is easily adapted for use with drawn tubular membranes as well as membranes that are made by depositing a thin permselective metal layer onto a porous tube support. There are three significant variants to this module design. One is based on the membrane tubes fixed to a header at each end of the membrane tube. The second is similar in that both ends of the membrane tubes are fixed to a header, but to the same header. In the second design, the membrane tubes are bent into a U shape, which can be easily done with small diameter metal tubes. The third is based on a single header, to which open sides of closed-one-ended membrane tubes are fixed. The closed-ends of the membrane tubes are suspended freely. This latter design is more common for commercial applications, due to free thermal expansion and greater membrane durability (see above discussion), whereas laboratory test-and-evaluation practices favor the first variant for its ease of assembly. If the membrane is a drawn, thin-walled tube, the membrane tube will usually be brazed to the header. This is more difficult if the membrane tubes are to be fixed at both ends to head-... 

Hatanaka T, Takeshita T, Murata H, Hasegawa N, Asano T, Kawasumi M, Morimoto Y (2008) Electrode and membrane durability issues of PEFCs. ECS Trans 16 1961-1965... 

Fenton s test, which consists in the immersion of the membrane in a H2O2 solution (30 w/w%) containing 20 ppm of Fe, monitoring the rate of fluoride ions release into the solution, has become a common ex situ accelerated test for membrane durability [91, 92]. Fenton test usually yields lifetimes much greater... 

Most of the commonly used membranes used in DMFC exhibit acceptable performance stability after thousands of hours under steady-state operation, including perfluorinated sulfonic acid, PTFE-co-HFP radiation-grafted poly- styrenes, and sPAE [85]. However, membrane durability results under unsteady-state operation are stUl scarce. Siroma et al. [114] have shown that a significant fraction of Nation dissolved after 1 week of DMFC operation with methanol solution. 

D.L. Peet, Membrane Durability in Chlor-Alkali Plants, In F. Hine, W.B. Darlington, R.E. White, and R.D. Varjian (eds). Electrochemical Engineering in Chlor-Alkali and Chlorate Iruiustries, PV 88-2, Electrochemical Society (1988), p. 329. 

Schiraldi DA (2006) Perfluorinated polymer electrolyte membrane durability. Polym Rev 46 315-327... 

Ralph TR, Barnwell DE, Bouwman PJ, Hodgkinson AJ, Petch MI, Pollington M (2008) Reinforced membrane durability in proton exchange membrane fuel cell stacks for automotive applications. J Electrochem Soc 155 B411-B422... 

---