Transport properties gases

The effect of the substituents on chain mobility and chain packing has been related to the gas transport properties [209]. Role of symmetry of methyl group placement on bisphenol rings in PES shows the permeability coefficients in the following order ... 

The difference in temperature between the tube wall and the water is small, typically less than lOK in the convection section. Therefore, little error is introduced by using the water temperature as in the evaluation of the gas transport properties. 

Gas transport properties for the products of combustion of the common fuels, fired at normal excess air at or nearfull boiler load, may be obtained from Tables 23.1-23.4. Non-luminous gas radiation has a small overall effect in the convective section, typically 2-5 per cent of total convection. It may therefore be neglected for a conservative calculation. 

The zeolite-alumina tube is no more gas-tight after the thermal treatment. The presence or absence of the V-AI2O3 toplayer in the starting support does not influence the gas transport properties of the final zeolite-alumina tube. 

Guizard, C., Bac, A., Barboiu, M. and Hovnanaian, N. (2000) Organic-inorganic hybrid materials with specific solute and gas transport properties for membrane and sensors applications. Molecular Crystals and Liquid Crystals, 354, 91-106. 

Uhlhom, R. J. R., K, Keizer and A. J. Burggraaf. 1989. Formation of and gas transport properties in ceramic membranes. In Advances in Reverse Osmosis and Ultrafiltration eds. T. Matsuura and S. Sourirajan, pp. 239-59. Nat. Res. Council Canada, Ottawa. 

Uhlhom, R. J. R. 1990. Ceramic Membranes for Gas Separation Synthesis and Gas Transport Properties, Ph.D. thesis, University of Twente, Enschede. 

Cellular Polymers 111. Conference proceedings. Coventry, 27th-28th April 1995, paper 14. 6124 INFLUENCE OF LOW MOLECULAR ADDITIVES ON GAS TRANSPORT PROPERTIES IN POLYETHYLENE FILMS AND FOAMS... 

So far, it appears that the gas transport properties of glassy polymer membranes, manifested in a decreasing P(a), or increasing D(C), function can be adequately represented by the above dual diffusion model with constant diffusion coefficients Dl5 D2 (or Dtj, DX2). We now consider the implications of this model from the physical point of view ... 

Figure 2.24 Correlation of the oxygen permeability coefficient for a family of related polysulfones with inverse fractional free volume (calculated using the Bondi method) [33]. Reprinted with permission from C.L. Aitken, W.J. Koros and D.R. Paul, Effect of Structural Symmetry on Gas Transport Properties of Polysulfones, Macromolecules 25, 3424. Copyright 1992, American Chemical Society...

Harrington, J.F. and Horseman, S.T. (1999) Gas transport properties of clays and mudrocks. In Geological Society, Special Publications, London, pp. 107-124... 

We report here on the structure and gas transport properties of asymmetric membranes created by the Langmuir-Blodgett deposition of ultra-thin polymeric lipid films on porous supports. Transmission and grazing angle FTIR spectroscopy provide a measure of the level of molecular order in the n-alkyl side-chains of the polymeric lipid. The level of orientational order was monitored as a function of the temperature. Gas permeation studies as a function of membrane temperature are correlated to the FTIR results. 

We report here on the structure and gas transport properties of asymmetric membranes produced by the LB deposition of a polymeric lipid on porous supports. The effects of temperature on the structure and gas transport is described. The selectivity of CO2 over N2 permeation through the LB polymer films is determined. The polymerized lipid used in this study contains tertiary amines which may influence the CO2 selectivity over N2. The long term objective of our work is to understand how structure and chemistry of ultrathin films influence the gas permeation. 

For gas separation membranes, for example, He, O2, and N2 gas transport properties of CA/poly(methyl methacrylate) (PMMA) blends have been measured [108]. This article reported that CA/PMMA blends exhibited phase separation with limited intermiscibility between the components, but they were possibly useful as membrane materials to produce high-purity helium gas streams combined with high helium recovery. 

Bondar VI, Freeman BD, Pinnau I (2000) Gas transport properties of poly(ether-b-amide) segmented block copolymers. J Polym Sci Part B Polym Phys 38(15) 2051-2062... 

In this situation, a film is grown on the hot surface (Tw), and its thickness will increase without limit as long as fresh reactants are provided and products can be removed. The gas state will be in quasiequilibrium far from the hot surface and in a strongly nonequilibrium condition close to it. The change from one to the other will occur across a boundary layer where temperature, velocity, and species concentration vary rapidly. The behavior of this boundary layer will be determined by gas transport properties such as viscosity, thermal conductivity, as well as gas-phase kinetics and diffusion coefficients. So, even if the kinetics at the surface are very fast, we must deal with quasiequilibrium phenomena where gas conditions vary rapidly over short distances. 

Gas transport properties through silica membranes have not been extensively studied. Especially the resistance of gas transport of small molecules like H2 through the thin SiC>2 layer are currently such that the resistance in the supporting layers should not be ignored or might even dominate the transport properties of the final membrane, see for example [50],... 

EFFECT OF PHYSICAL AGEING ON THE GAS TRANSPORT PROPERTIES OF PVC AND PVC MODIFIED WITH PYRIDINE GROUPS... 

Gas transport properties are required to apply the theory given in Sections 3.3 and 3.4. Viscosities of pure nonpolar gases at low pressures are predicted from the Chapman-Enskog kinetic theory with a Lennard-Jones 12-6 potential. The collision integrals for viscosity and thermal conductivity with this potential are computed from the accurate curve-fits given by Neufeld et al. (1972). 

Pellegrino J, Wang D, Rabago R, Noble RD, and Koval CA. Gas transport properties of solution-cast perfluorosufibnic acid ionomer films containing ioninc surfactants. J. Membr. Sci. 1993 84 161-169. 

M. E. Rezac, J. D. Le Roux, H. Chen, D. R. Paul, and W. J. Koros, Effect of mild solvent post-treatments on the gas transport properties of glassy polymer membranes. Journal of Membrane Science 90, 213-229 (1994). 

C.L. Lin et al. [71] reported deposition of silica layers (plugs) with a thickness of about 1.5 pm within the pores of commercial, mesoporous y-alumina films (pore diameter 4 nm, thickness 1-3 pm) on a-alumina supports (US filter). The deposits were obtained by reaction of TEOS-oxygen (10-20%) mixtures in He as carrier gas applied in the OSG mode to the mesoporous layer. No further details (e.g., temperature or pressure) were given. Depending on these unknown conditions, dense as well as microporous silica membranes with pores down to estimated values of 0.4-0.6 nm were obtained. These membranes have interesting combinations of permselectivity and flux values for several gas combinations (see Chapter 9 on gas transport properties). 

The polyimide is prepared from 1,5 naphthlene diamine (1,5 ND) and 3,3, 4,4 diphenylhexafluoroisopropylidene tetracarboxylic acid dianhydride (6F). A polyamide acid is obtained initially and this is cyclized to give the polyimide. Because polyimides are derivatives of polyamides, polyimides are often included in reviews of aromatic polyamides. Another reason polyimides are included in this paper is that they illustrate the role of Structure Level II on gas transport properties in a straightforward manner. 

Table 7.1 The specific requirements, advantages and disadvantages connected to mobile carrier systems with respect to their selective gas transport properties...

The characteristics discussed above are mainly related to clustering in the ionic phase, but the role of the hydrophobic phase also is quite important. In some cases it controls the gas transport properties of the material (e.g. 02 through PFSA) (4). And, it makes it possible to keep hydrophobic reactions in the neighborhood of the ionic domain species (5). Moreover, metal complexes with bulky hydrophobic ligands can be supported in the ionomers because of synergystic interaction of both polymer phases (6). Interesting electrocatalytic or photocatalytic systems take advantage of these unique properties of ionomers (7-8). Moreover, support of the reactants in ionomers may be useful for reactant/product separations. 

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