EVALUATION OF SODIUM STEARATE AS A SYNERGIST FOR ARYLAMINE ANTIOXIDANTS IN SYNTHETIC LUBRICANTS

Differential scanning calorimetry (DSC) was employed to evaluate the p erformance of an eater lubricant containing sodium stearate. In the is othermal DSC oxidation test, sodium stearate is an effective synergist for arylamine antioxidants such as p,p'-dioctyldiphenylamine (DODPA). When combined with arylamine antioxidants, sodium stearate can also e ffectively reduce the increases in viscosity and acid number of the es ter oil in oxidation-corrosion tests. The electron paramagnetic resona nce (EPR) results indicated that sodium stearate can reduce the free r adical contents in the oxidized oil in the presence of arylamine antio xidants.