Oxygen barrier behavior

Effect of RH on OPV. It was also of interest to determine the factors which lead to a decrease in OPV with increasing RH in amorphous polyamides. As noted above, this behavior is unique for commercial oxygen barrier materials. This phenomena, however, appears to be general for amorphous polyamides, so the discussion which follows will assume that the OPV decrease is caused by the same effect in all cases. 

Gas and water-permeability PLA has insufficient barrier behavior to oxygen, carbon dioxide, and water vapor compared to other benchmark packaging polymers such as polyolefins (PE, PP) and PET [19]. 

Mount III, Eldridge, M., Wagner, John R., Aroma, Oxygen and Moisture Barrier Behavior of Coated and Vacuum Coated OPP Films for Packaging , /. Plastic Film Sheeting, V17(July), 2001, pp 221-237. 

Surface science studies of CO oxidation on Au(llO) single crystals have been made previously in which a Pt filament was used to adsorb oxygen adatoms ( o 0.25) on the Au(llO) surface and a CO titration was performed subsequently (7). CO did react to form CO2 with Eapp = 2 1 kcal/mole. Since CO was not observed to adsorb on Au(llO) at 125 K, it is only physisorbed (as on Au(lll)) and we can estimate that Elh = 7 kcal/mol on Au(llO). The difference from Au(lll) is probably due to a weaker Au-O bond on Au(lll) which leads to a lower barrier for reaction. No surface carbonate was formed from CO2 + Oa on Au(llO) either (7). This is in contrast to the behavior on Ag. Exposing oxygen covered Ag(llO) (16) or Ag(lll) (17) to CO2 produces carbonate species which are stable to 485 K on the surface. 

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