Water transport properties

Effects of annealing are also observed on the water transport properties. Both the diffusional permeability and the permeability under osmotic pressure decrease in comparison with the sample before annealing (Table IV). Moreover, the g ratio also decreases, which, in terms of the equivalent pore radius, means that the membrane becomes tighter upon annealing. 

Copolymers having enhanced oxygen permeability and water transport properties consisting of 3-methacryloxypropyltris(trimethyl-siloxy)silane, (V), and 2-methacryloyloxymethyl-18-crown-6, (VI), were prepared by Salamone et al. (6) and used as contact lenses. 

T.A. Zawodzinski, J. Davey, J. Valerio, and S. Gottesfeld. Water transport-properties of various fuel-cell ionomers. Abstracts of Papers of the American Chemical Society 205, 75-PMSE 1993. 

Morooka, H., and Niwa, M., Moisture and Water Transport Properties of Clothing Materials and Comfort Sensations, J. Home Econ. Jpn, 30, 320 (1979)... 

The use and design of polymers in the food packaging industry requires an understanding of the water transport properties of the... 

Osmotic phenomena have been observed since the middle of the eighteenth century. The first experiments were conducted with animal membranes and it wasn t unitl 1867 that artificial membranes were employed. In the early 1950 s, research workers at the University of Florida demonstrated, with thick films, that cellulose acetate possessed unique salt and water transport properties which made it potentially attractive as a reverse osmosis desalination membrane. During the 1960 s, Loeb and others at the University of California at Los Angeles developed techniques to prepare cellulose acetate membranes with an economical water flux and salt rejection at moderate driving pressures. With this development, reverse osmosis became a practical possibility. 

The preparation of a GDL involves the use of a substrate, carbon cloth or paper [6-8], which are in general commercially available. They are usually treated to have hydrophobic/hydrophilic properties, typically using polytetrafluoroethylene (PTFE) [9]. A microporous carbon layer, made with carbon and PTFE with controlled porosity is applied to the substrate in the catalyst layer side or to both sides [10]. This improves the gas and water transport properties. 

NAFION incorporated with Si02, Ti02, or Zr(HP04)2 nanoparticles exhibits enhanced performance in PEMFCs compared to fiUer-free NAFION at elevated temperatures under low RFl. The water transport properties, which were investigated by PFGSE NMR, spin—lattice relaxation Ti, and NMR spectroscopy, revealed at least two distinct water environments. The enhanced water uptake relative to fiUer-free NAFION was attributed to alteration of the pore structure of the membrane [80]. 

The water transport properties were measured in normal osmosis experiment. Deionized water and aqueous solution of KCl of 10wt% were placed in each of the two chambers of... 

Miguel, O. and Iruin, J. J. (1999a). Water Transport Properties in Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers. Journal of Applied Polymer Science 73,455-468. 

Ma Y, Hu J, Ma H, Yi B, Zhang H. Effect of water transport properties on a PEM fuel cell operating with dry hydrogen. Electrochim Acta 2006 51 6361-6. 

Aotani, K., Miyazaki, S., Kubo, N., and Katsuta, M. 2008. An analysis of the water transport properties of polymer electrolyte membrane. CS Tmns., 16, 341-352. 

Ye, X., and Wang, C. Y. 2007. Measurement of water transport properties through membrane-electrode assemblies. ZSecfroc ggjj 5oc., 154, B676-B682. 

Verbrugge and Hill (1990) presented the theoretical representation and experimental data to characterize the proton and water in perfluorosulfonic acid membrane. The analysis describes the transport of water molecules carried along with the transport of proton across the membrane. Springer et al. (1991) presented a one-dimensional, isothermal model of FEMFC in which detailed considerations of the Nafion-117 membrane characteristics in terms of water content and water transport properties including water drag coefficient and diffusion coefficient are given. Their results demonstrated increased membrane resistance with current density. 

Water transport properties (diffnsion, hydraulic permeability, and electroosmotic... 

Catalyst powder deposition In catalyst powder deposition described by Bevers et al. (1998) the components of the catalytic layer (Vulcan XC-72, PTFE powder, and a variety of Pt/C loadings) are mixed in a fast mnning knife mill under forced cooling. This mixture is then applied onto a wet-proofed carbon cloth. Also applying a layer of carbon/PTFE mixture flattens out the roughness of the paper and improves the gas and water transport properties of the MEA. 

---