Study Demonstrating Enhanced Oxidation Stability when Arylamine Antioxidants are Combined with Organic Molybdenum Complexes

An oil-soluble additive organic molybdenum complex (MC) was synthesized. The antioxidation properties of a formulation including polyalphaolefin synthetic lubricant (PAO), the complex of p,p.-dioctyldiphenylamine (DODPA) and MC, were evaluated by a differential scanning calorimetry (DSC) test and oxidation-corrosion (OC) tests. The DSC test measures the incipient oxidation temperature (IOT) and oxidation induction time (OIT) of the lubricant at high temperature and the oxidation stability of the oil including viscosity and the total acid number increase are measured by the OC test. In the first test,the IOT and OIT of the PAO containing DODPA were improved respectively after combining with MC. In the oxidation-corrosion test, in comparison to the base fluid, the additive hardly exhibited antioxidation properties, but the combination of MC with DODPA showed a reduction in viscosity increase of about 32.4%. The total acid number increase was 25.4% less than those of the lubricants containing DODPA. In the modified Penn State Micro-Oxidation Test (MPMOT), the combination of DODPA with MC exhibits good deposit inhibition in PAO. These results indicate that MC shows good oxidative synergisms with the DODPA antioxidant. In addition, the changes occurring to DODPA in the oxidation of the PAO with and without MC were followed by gas chromatography mass spectrometer (GC/MS) measurements. Finally, the antioxidation synergism of the formulation of MC with DODPA was proposed.