Effect of relative humidity on oxygen

Neyerlin KC et al (2005) Effect of relative humidity on oxygen reduction kinetics in a PEMFC. J Electrochem Soc 152(6) A1073-A1080... 

Neyerlin, K. C., Gasteiger, H. A., Mittelstaedt, C. K., Jorne, J., and Gu, W. (2005) Effect of relative humidity on oxygen reduction kinetics in a PEMFC. Journal of the Electrochemical Society 152(6), A1073-A1080. 

Neyerlin K C, Gasteiger H A, Mittelsteadt C K, Jome J and Gua W (2005) Effect of Relative Humidity on Oxygen Reduction Kinetics in a PEMFC, J. Electrochem. Soc., 152, pp. A1073-A1080. 

One of the frequently advertised advantages of the phosphoric acid imbibed polybenzimidazole systems is their zero water drag coefficient and their possibihty to operate with dry hydrogen and oxygen. However, a vast literature has been devoted to the study of the proton conduction and the effect of relative humidity on the conductivity of the PBl-phosphoric acid system. The promoting effect and the physicochemical interactions of water vapors with the polymer electrolyte and on the fuel cell performance have been explicitly shown for the PBl/PPy(50)coPSF 50/50 polymer blend imbibed with phosphoric acid under fuel cell conditions. ... 

TABLE 12.2 Effect of Relative Humidity on the Oxygen Permeability of Some Conventional Polymers at 23° C... 

Figure 10. The influence of environment on the wear of three carbon filled PTFE composites, (a) the effect of relative humidity in air, (b) the effect of oxygen (as air) compared with nitrogen at a nominal zero humidity. The three carbons are ...

Another sensor type [158] utilizes the effect of water vapor on the fluorescence quantum yield of adsorbed fluorophores. Thus, a silica-gel-adsorbed perylene dy when excited with an LED at 490 nm, shows a ca 90 Fo reduction in fluorescence on going from 0 to 100% relative humidity. Although this sensor covers the whole humidity range, the response is not linear, and oxygen interferes to some atent. 

The effect of plasticizers and temperature on the permeabiUty of small molecules in a typical vinyUdene chloride copolymer has been studied thoroughly. The oxygen permeabiUty doubles with the addition of about 1.7 parts per hundred resin (phr) of common plasticizers, or a temperature increase of 8°C (91). The effects of temperature and plasticizer on the permeabiUty are shown in Figure 4. The moisture (water) vapor transmission rate (MVTR or WVTR) doubles with the addition of about 3.5 phr of common plasticizers (92). The dependence of the WVTR on temperature is a Htde more comphcated. WVTR is commonly reported at a constant difference in relative humidity and not at a constant partial pressure difference. WVTR is a mixed term that increases with increasing temperature because both the fundamental permeabiUty and the fundamental partial pressure at constant relative humidity increase. Carbon dioxide permeabiUty doubles with the addition of about 1.8 phr of common plasticizers, or a temperature increase of 7°C (93). 

The permeation of simple gases in polar polymers is also dependent on relative humidity because of the water s strong interaction with the polymer. Particularly large is the effect of humidity on the oxygen permeability of barrier layers made from EVOH. At 20 °C and 100 % relative humidity the permeability is 300 times higher than at 0 % relative humidity at the same temperature. By orientation and thermal treatments the barrier properties at high relative humidity can be significantly improved (up to a factor of 10). 

Although the importance of environmental factors (temperature, rela-- -tive humidity, airborne contaminants, and oxygen) that affect the fading of dyed textiles exposed to artificial and natural light indoors is well documented (1,2), relatively little information exists on the effectiveness of UV stabilizers incorporated into plastic films to minimize or retard such fading. To obtain this information, light-sensitive blue wool fabric (AATCC L-4 standard) was exposed to light from a xenon-arc source, with and without protection by clear cellulose acetate films... 

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