Evaluation on Synergistic Antioxidation of Molybdenum Dialkydithiocarbamate with Arylamine Antioxidant

The antioxidation properties of molybdenum dialkyldithiocarbamate (M 807)- and p,p-dioctyldiphenylalmine (V 81)- or mixed octylated and butylated diphenylalmines (V 961)-containing poly-α-olefin (PAO)-derived lubricants were evaluated by differential scanning calorimetry (DSC) and modified penn state micro-oxidation test (PMOT). DSC test measures incipient oxidation temperature (OT) and oxidation induction time (IT) of the lubricant at high temperatures and the oxidation stability of oil weight loss is measured by PMOT test. DSC test shows that OT and IT of V 81-or V 961-containing PAO were improved significantly by M 807 addition. PMOT test indicates that when combining with V 81 antioxidants, M 807 can also effectively reduce the increase in weight loss of PAO and deposits formed in oils. These results suggest that M 807 shows a good antioxidative synergism with alkylated diphenylamine antioxidants. In addition, FTIR results from PMOT test confirm that addition of M 807 can significantly enhance the oxidation induction time of oils containing V 81 and inhibit formation of oxidation products including carbonyl bonds or hydroxyl group. Finally, the proposed mechanism of the inhibition involves a synergy between M 807 and arylamine antioxidants.