Oxygen diffusion and solubility

Based on literature sources and assuming an Arrhenius-type equation to hold, values of D (31) and Cq (32) at 20 and 30 C have been used to estimate the apparent activation energies for oxygen diffusion and solubility to be... 

Chatenet, M., Aurousseau, M. and Durand, R. (2000). Electrochemical Measurement of the Oxygen Diffusivity and Solubility In Concentrated AUcahne Media on Rotating Ring-disk and Disk Electrodes Application to Industrial Chlorine-soda Electrolyte, Electrochim. Acta, 45, pp. 2823-2827. 

Keywords Interlayer adhesion loss Epoxy coatings Weathering Erosion mechanism UV absorber Humidity Water Crosslinking Network degradation Oxygen diffusion and solubility Photoproducts Oxidation zone Rain Lag time UV radiation degradation... 

Table 5. Diffusion and Solubility Coefficients for Oxygen and Carbon Dioxide in Selected Polymers at 23°C, Dry ...

The diffusion and solubility coefficients for oxygen and carbon dioxide in selected polymers have been collected in Table 2. 

The use of siloxane polymers in applications such as separation membranes, drug release systems, and blood oxygenators requires extensive permeability studies. This, of course, also involves measurements of diffusivity and solubility.16... 

The temperature dependence of the polarographic current is deduced from that of the oxygen diffusion and permeation coefficients and of the oxygen solubility in the membrane and media. With increasing temperature the polarographic current rises and the response time becomes shorter. 

The diffusion and solubility coefficients for oxygen and carbon dioxide in selected polymers have been collected in Table 5. Determination of these coefficients is neither common, nor difficult. Methods are discussed later. The values of S for a permeant gas do not vary much from polymer to polymer. The large differences that are found for permeability are due almost entirely to differences in D. 

Seguchi, T., and Yamamoto, Y, Diffusion and Solubility of Oxygen in f-ray Irradiated Polymer Insulation Materials, Japan Atomic Energy Research Institute report, JAERl 1299, Takasaki, Japan, 1986. 

Pullulan (10 g 300) is a water-soluble a-(l-46)-D-maltotiiose polymer with some a-(l->3) links from fungi. It forms foils that are quite resistant to oxygen diffusion and are therefore used as packing material for food. Table 4.2.1 names a few common polysaccharides from natural sources. 

The permeability coefficient, P, combines the effects of the diffusion and solubility coefficients. The barrier characteristics of a polymer are commonly associated with its permeability coefficient values. The well-known relationship P = DS holds when D is concentration independent and S follows Henry s law. Standard methods for measuring the permeability of organic compounds are not yet available. ASTM E96 describes a method for measuring the water vapor transmission rate. ASTM D1434 describes a method for the determination of oxygen permeability. 

Diffusion and solubility of water in melts was first studied in detail by Scholze and co-workers around 1960. Very little additional work was done in this area until recent years, when the replacement of air by pure oxygen in the firing of glass tanks resulted in a considerable increase in the hydroxyl content of commercial glasses. Replacement of air by oxygen for combustion reduces the formation of nitrous oxides, and thus reduces the air pollution created by the glass manufacturing process. 

Chatenet M, Aurousseau M, Durand R (2000) Comparative methods for gas diffusivity and solubility determination in extreme media application to molecular oxygen in an industrial chlorine-soda electrolyte. Ind Eng Chem Res 39 3083-3089... 

The effect of copolymer composition on free volume and gas permeability of PECT copolymers as well as PET and PCT homopolymers was studied by Hill et al. (97). The free volume was studied by positron annihilation lifetime spectroscopy (PALS) in order to determine the relative size and concentration of free volume cavities in the copolymers. The logarithm of the permeability to oxygen and carbon dioxide increased linearly with the %mol content of 1,4-CHDM units in the copolymer, which was in agreement with the free volume cavity size and relative concentration observed by PALS measurements. Light et al. (98) studied the effect of sub-T relaxations on the gas transport properties of PET, PCT and PECT polyesters. They observed that modification of PET with 1,4-CHDM increased the magnitude of the p-relaxation, as well as the diffusion and solubility coefficients for oxygen and CO. ... 

Oxygen and Hydrogen Diffusivity and Solubility in Phosphoric Acid... 

As reported in literature the diffusivity and solubility of oxygen and hydrogen in phosphoric acid depends on the temperature and concentration [148-152]. Furthermore, it was suggested that the diffusivity and solubility exhibit exponential reciprocal temperature dependence. Various polynomial functions were used to correlate these properties with experimental data (Table 18.3). 

Table 18.3 Selection of modeling equations for the oxygen and hydrogen diffusivity and solubility in phosphoric acid... 

Oxygen diffusion and its solubility in a polymer matrix evidently decide the kinetics of oxidation and photo-oxidation. 

The presence of crystalline domains in a polymer matrix has two effects on oxygen diffusion and its solubility behaviour ... 

The aforementioned cathodic reaction products are not soluble in the nonaqueous electrolyte, which leads to precipitation of the lithium oxide or peroxide in the pores of the carbon-based air cathode. This results in blockage of the porous pathways for oxygen diffusion and coverage of the active catalytic sites for reaction. 

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