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•Commarolal automotlva hibrloanta 8F-CD ••Unraaotad only

Figure 3

In these microoxidation tests, the rates of the primary oxidation and the condensation polymerization can be significantly affected by the presence of certain metals in the catalyst cup. For example, iron and ferrous alloys have a strong catalytic effect on both primary and condensation polymeric reactions. On the other hand, when present in sufficient quantities, copper has an inhibiting effect on both primary and condensation polymerization reactions. A variety of iron and cromium oxides which have been evaluated as ceramic materials used in magnetic storage media also show a strong catalytic effect on both oxidation reactions. Quartz and glass test cups have been used as examples of noncatalytic

•Commarolal automotlva hibrloanta 8F-CD ••Unraaotad only test conditions. At 250°C, based on the chemical kinetic model the oxidation rate should increase by a factor of 4 over 225°C. Data on Figure 4 for two aircraft gas turbine oils show 40 and 30 percent oxidized in 20 and 25 minutes test time, respectively. The TCP and TXP phosphate esters show 5 percent or less oxidation after 30 minutes at 250°C. The diphenyl, ditertiary butyl phenyl phosphate, on the other hand, shows essentially no measurable oxidation after 5 hours at 250°C. At 270°C where the rate of oxidation for the automotive, diesel, and aircraft gas turbine lubricants is too high to survive for a significant test time, the TCP and TXP show 5 and 6 percent oxidized in 15 minutes, while the diphenyl, ditertiary-butyl-phenyl phosphate still appears to be essentially stable after 3 hours. The polyphenyl ether has been shown to have oxidative stability in microoxidation tests comparable to these aryl phosphate esters.

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