Permeability of oxygen

PERMANENT GASES Table 3 lists the permeabilities of oxygen [7782-44-7] nitrogen [7727-37-9] and carbon dioxide [124-38-9] for selected barrier and nonbarrier polymers at 20°C and 75% rh. The effect of temperature and humidity are discussed later. For many polymers the permeabihties of nitrogen, oxygen, and carbon dioxide are in the ratio 1 4 14. 

In the second category, SECMIT has been used to probe the relative permeability of oxygen between water and DCE or NB, with no supporting electrolyte present in any phase. Under the conditions employed, direct voltammetric measurements in the organic phase would be impractical due to the high solution resistivity (DCE or NB) or limitations of the solvent window available (NB). Figure 24 shows the steady-state current for the... 

The effects of equivalent weight (FW = g polymer/mol SO3H) and water content on diffusion coefficient, solubility, and permeability of oxygen for fully hydrated BAM, S-SEBS, ETFE- -PSSA, Nafion 117, and BPSH membranes have been studied. It has been found that the diffusion coefficients of all the studied membranes decrease with increasing EW, while the solubility correspondingly increases. These trends are the same as found in... 

The permachor method is an empirical method for predicting the permeabilities of oxygen, nitrogen, and carbon dioxide in polymers. In this method a numerical value is assigned to each constituent part of die polymer. An average number is derived for the polymer, and a simple equation converts the value into a permeability. This method has been shown to be related to the cohesive energy density and the free volume of the polymer. The model has been modified to liquid permeation with some success. 

If the aim of excipient compatibility is to be predictive of the degradation expected with clinical or commercial dosage forms, then the packaging configuration should be representative of what will be used in that setting. Factors that could influence stability measurements include container headspace and permeability of oxygen and water vapor through the walls and cap (if a bottle) of the container. 

From these results, the permeability of oxygen in a Nation film can be obtained as the product of its concentration by its diffusion coefficient in the film DfCf. Figure 1.15 shows the variation of the oxygen permeability with the temperature. Like many perfluorinated materials, the Nation membrane is especially a good solvent of oxygen. 

For barrier coatings to be effective it is necessary to have (i) good adhesion of the barrier film on the metal surface (this is generally accomplished by multicoat procedure to a certain extent) (ii) proper choice of the polymers to control the permeability of oxygen and (iii) optimum film thickness achieved by multicoats or thin-film system, depending upon the envisaged application. 

FieldnerAC, Katz SH, Kinney SP. 1921. Permeability of oxygen breathing apparatus to gasoline vapors. Technical Paper 272. U.S. Bureau of Mines. 

Equations (47-49) describe the nature of the losses incurred by transport within the catalyst layer. The catalyst surface area (catalyst sites) active in the ORR process of conversion of oxygen flux to protonic current flux (Eq. 49) is distributed linearly along the thickness of the catalyst layer. Consequently, gas supply to a catalyst site removed from the backing layer/catalyst layer interface is limited by the effective permeability of oxygen in the catalyst layer,... 

The gas diffusion layers, one next to the anode and the other next to the cathode, are usually made of a porous carbon paper or carbon cloth, typically 100 pm to 300 pm thick. Fig. 14 shows a porous GDL made of carbon paper, which is partially covered by catalyst layer. The porous nature of the backing layer ensures effective diffusion of feed and product components to and from the electrode on the MEA. The correct balance of hydrophobicity in the backing material, obtained by PTFE treatment, allows the appropriate amount of water vapor to reach the MEA, keeping the membrane humidified while allowing the liquid water produced at the cathode to leave the cell. The permeability of oxygen in the GDL affects the limiting current density of ORR, and thus the performance of PEMFC.[ l... 

The permeabilities of oxygen through the Vycor were constant with the pressure difference and decreased with the square root of the temperature (figure not included). So the main mechanism for gas permeation is Knudsen diffusion. However, the permeabilities of oxygen through the V20s-coated catalytic membrane were deviated from Knudsen diffusion. As the partial oxidation proceeded, the... 

The V206-coated catalytic membrane was applied to the partial oxidation reaction to produce maleic anhydride from 1-butene. The maximum selectivity was 95% at 350 °C and the permeability of oxygen through the V20s-coated catalytic membrane was enhanced. More careful studies are needed about this permeability enhancement. 

Gas Permeation. Permeability of oxygen and nitrogen was evaluated for supplied air by a gas chromatographic method (Yanaco GTR-20). 

Plasticized polymers have been observed to behave like miscible blends. The permeabilities of oxygen, carbon dioxide, and water vapor in a vinybdene chloride copolymer increase exponentially with increasing plasticizer (4,5,28). About 1.6 parts plasticizer per hundred parts polymer is enough to double the permeablity. 

Permeability of oxygen Bending strength Tensile strength Hygroscopicity... 

Table 4.4 Effect of Density on the Permeability of Oxygen and Water in Polyethylene...

Solvents are used to carry dissolved or suspended resin and evaporate from the coating after application. Additives in small amounts are used as mildew inhibitors (cuprous compounds), surface-drying additives (manganese and cobalt naphthanates), and barrier-forming additives to protect the resin from heat and UV degradation. Fillers (talc and mica) decrease the permeability of oxygen and water in the coating. 

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