Permeability and diffusion

By far the most widespread use of NMR in an on-line production environment is the utilization of downhole exploration tools by petroleum service companies such as Schlumberger, Halliburton, and Baker Hughes. Articles on these unilateral NMR systems are found in the patent databases, " academic literature, and on-line resources provided by the exploration companies. The references provided here are just a few examples in a very prolific field. The technique is applied in high-temperature and pressure situations and currently is used down to a depth of about 10 km (6 miles) to produce a picture of water/oil content in the adjacent rock formations as well as to derive permeability, diffusivity, and hydrocarbon chemistry information. Mobile unilateral NMR systems such as the NMR-MOUSE are also being developed in order to take benchtop NMR systems into the field to perform analysis of geological core samples at the drill site. NMR analyzers are also being developed to determine the bitumen content and properties in tar sand production and processing. " " ... 

Table 9—Computed values of permeability, diffusion and partition coefficients for different formulations...

Table 17.7 summarizes the effects of the microstructural factors on the microscopy fractal dimensions, Dj, y, and Zlpr- Different fractal dimensions reflect different aspects of the microstructure of the fat crystal networks and thus have different meanings. It is necessary to define which structural characteristic is most closely related to the macroscopic physical property of interest (mechanical strength, permeability, diffusion) and then use the fractal dimension that is most closely related to the particular structural characteristic in the modeling of that physical property. 

Permeability, Diffusion and Sorption Coefficients, as well as Their Ideal Ratios, for Vapors of C2H4 and C2H6... 

Comparative Permeability of C2, C3, and C4 olefins. It is interesting to compare permeability, diffusion, and solubility coefficients of various olefins, as well as ideal olefin/paraffin selectivity in a glassy polymer. Such comparison can be made,... 

Variables such as density, albedo, light e-folding depth, specific surface area (SSA), crystal size and shape, heat conductivity, permeability, diffusivity and shear resistance are required for a complete physical description of the snowpack. Not all these variables have major relevance to climatic issues. Albedo, i.e. the fraction of incident light that is reflected, has obvious climatic relevance and is discussed here. It depends in part on crystal size and shape and this dependence can in fact more simply be related in part to the SSA of the snow i.e. the surface area accessible to gases per unit mass. ... 

The permeability, diffusion, and solubility coefficients for the gases as well as the ideal separation factors for gas pairs have been determined. A poly(imide-siloxane) with 20% siloxane content shows the best compromise with very high permeability and a still high permselectivity for the CO2/CH4 gas pair [12]. 

Table 3.7 Permeability, diffusion and solubility coefficients of gases in PTMSN and PTMSP127P...

Relations between Permeability, Diffusion, and Solubility Coefficients... 

When the permeability, diffusion, and solubility coefficients are functions of pressure their experimental values are mean values (P,D, and S) for the pressures applied at the membrane interfaces, cf., eqs. (61.6-61.8). Equations (61.12-61.14) are applic able als o to P, D, and 5 over a limited range of temperatures. The activation energies Ep and Ed commonly decrease with increasing pressure. 

The dependence of permeability, diffusion, and solubility coefficients on penetrant gas pressure (or concentration in polymers) is very different at temperatures above and below the glass transition temperature, Tg, of the polymers, i.e., for mbbery and glassy polymers, respectively. Thus, when the polymers are in the rubbery state the pressure dependence of these coefficients depends, in turn, on the gas solubility in polymers. For example, as mentioned in Section 61.2.4, if the penetrant gases are very sparsely soluble and do not significantly plasticize the polymers, the permeability coefficients as well as the diffusion and solubility coefficients are independent of penetrant pressure. This is the case for supercritical gases with very low critical temperatures (compared to ambient temperature), such as the helium-group gases, Ha, Oa, Na, CH4, etc., whose concentration in rubbery polymers is within the Heruy s law limit even at elevated pressures. 

Subcritical gases, such as organic vapors, are much more highly soluble in polymers, and, consequently, the above behavior is observed only at very low pressures (or concentrations in polymers). As the penetrant pressure is raised, and the polymers are increasingly plasticized by the penetrant gas, the permeability, diffusion, and solubility... 

When the concentration of penetrant gases in glassy polymers becomes sufficiently high to plasticize the polymers, the permeability, diffusion, and solubility coefficients will deviate from dual-mode sorption behavior and increase as the pressure is raised. 

The movement of a material, such as a gas or liquid, in the body of a polymer. If the gas or hquid is adsorbed on one side of a test piece and given off on the other, the phenomenon is related to permeability. Diffusion and... 

Figure 7.20. Water vapor permeability, diffusion, and sorption coefficients vs. network composition for a SIN based on a polyurethane and an epoxy. 5)...

Andrio et al. reported the effect of temperature and pressure on the permeability, diffusion and solubility coefficients of N2, O2 and CO2 in NR reinforced with different amounts of cellulose. Rubber compounds were prepared by adding cellulose II, as 10% cellulose xanthate aqueous solution, to NR latex under stirring. Analysis of the results obtained by these authors... 

Neela, V. and von Solms, N., 2014. Permeability, diffusivity and solubility of carbon dioxide in fluoropolymers An experimental and modeling study. J. Polym. Res., 21 401. 

Permeability (P) is defined as the product of solubility (S) and diffusivity (D) of the gas into the polymer membrane and is temperature and pressure dependent. The permeability, diffusivity and solubility values of different gases in polydimethylsiloxane (PDMS) are collected in Table 22.1. 

Permeability, Diffusion and Solubility Coefficients of Alkanes Through Santoprene (Blend of Ethylene-Propylene Copolymer and Isotactic Poly(propylene)) Permeability, Diffusion and Solubility Coefficients of Esters Through Poly(epichlorohydrin)... 

TABLE 11. PERMEABILITY, DIFFUSION AND SOLUBILITY COEFFICIENTS OF ALKANES THROUGH SANTOPRENE ... 

Permeability, Diffusion and Solubility Coefficients of Esters through Poly(epichlorohydrin) VI/567... 

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