Polymeric membranes, general properties

Robeson LM. Correlation of separation factor versus permeability for polymeric membranes. J. Membr. Sci. 1991 62 165-185. Koresh JE and Soffer A. The carbon molecular sieve membranes. General properties and the permeability of CH4/H2 mixture. Sep. Sci. Tech. 1987 22 973-982. 

Despite concentrated efforts to innovate polymer type and tailor polymer structure to improve separation properties, current polymeric membrane materials commonly suffer from the inherent drawback of tradeoff effect between permeability and selectivity, which means that membranes more permeable are generally less selective and vice versa. 

In this section, we describe recent developments in water purification membranes, beginning with RO membranes, which are the tightest and nK t permselective, and proceeding to the more open UF and MF membranes. We d e with a diort discussion of liquid membranes, which are generally not polymeric membranes but vdiich merit consideration here because they are highly permselective, they are potentially useful in water purification, and they process certain unique and interesting properties. 

General Properties of Immobilized Liquid Membranes, Ion-Exchange Membranes and Polymeric Membranes... 

Abstract In this chapter fuel cell introduction and general concepts about fuel cell are presented. Types of fuel cell and their classification are given and desired properties of the polymeric membranes for use in PEMFC are desoibed. At the end challenges facing the fuel cell industry and their future outlook are briefly discussed. 

Because an ultrasonic wave propagates via compression and rarefaction, its velocity c is a property of the material in which it is being transmitted. In general, c increases with the density of the material. For example, c = 1500 m/s for water, whereas c 2000 m/s for a typical polymeric membrane material. 

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