Oxygen permeability coefficient equation

The oxygen permeability coefficient, P2, for the SiOx film in the SiOx-deposited PET film can be calculated from equation (3). 

Finally, using equation (3), the oxygen permeability coefficient for the deposited SiOx film itself was estimated and the result of the estimation is listed in Table V. The SiOx film deposited under no selfbias from the TMOS/O2 mixtures of 60 mol%02... 

The formula proposed by D Arcy should be modified when applied to gaseous phase diffusion. Hence, the compressibility of gas must be taken into accounf by introducing the mean value of pressure to the equation— A P +P ), where P, is an atmospheric pressure, and P —pressure under which the gas is forced. Therefore the gradient of pressure along the sample thickness L will be P2 Py Substituting with the oxygen viscosity as 2.02-10 N s/m at temperature 20°C, we get the permeability coefficient from the following formula ... 

The electrode was inserted vertically into distilled water. Distilled water was saturated with nitrogen gas to displace oxygen and other dissolved gases and then saturated with oxygen gas. The electrode was operated at -0.7v, and the reduction current was measured by use of a Hokuto Denko HM-101 anmeter. From the steady state current ioo of the permeation curve, the permeability coefficient P rcm (S.T.P.)-cm/cm -sec-cmHg] can be calculated by the following equation. 

Permeability, P, and difiusion coefficient, D, were obtained by performing a two-parameter least squares fit of the experimental flux data to equation (2). The solubility, S, was obtained from the relationship P = DS. The methodology of these oxygen barrier measurements, data analysis, and the sources of experimental error were previously described in detail elsewhere (7/). 

Carbon Dioxide Transport. Measuring the permeation of carbon dioxide occurs far less often than measuring the permeation of oxygen or water. A variety of methods are used however, the simplest method uses the Permatran-C instrument (Modem Controls, Inc.). In this method, air is circulated past a test film in a loop that includes an infrared detector. Carbon dioxide is applied to the other side of the film. All the carbon dioxide that permeates through the film is captured in the loop. As the experiment progresses, the carbon dioxide concentration increases. First, there is a transient period before the steady-state rate is achieved. The steady-state rate is achieved when the concentration of carbon dioxide increases at a constant rate. This rate is used to calculate the permeability. Figure 18 shows how the diffusion coefficient can be determined in this type of experiment. The time lag is substituted into equation 21. The solubility coefficient can be calculated with equation 2. 

Using the above mass balance equations, Kim et al. (2007b) were able to calculate the mass transfer coefficients for oxygen ko ) and acetate iJiAn) for several different membranes (Table 5.2). We see that Nafion is the most permeable to oxygen, with all three UF membranes much less permeable to oxygen. In contrast, the open pore size of the UF membranes made them quite permeable to acetate compared to the other membranes. The CEM membrane had the lowest permeability to acetate. 

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