7-di-iso-octyl-phenothiazine was measured in group Ⅰ
Ⅱ and Ⅳ base oils by rotating pressure vessel oxidation testing(RPVOT)
pressure differential scanning calorimetry(PDSC)and aging test
and its synergistic effect with 4
4′-di-iso-octyl-diphenylamine was examined. The results indicated that 3
7-di-iso-octyl-phenothiazine showed longer oxidation induction period and lower acid number increase than 4
4′-di-iso-octyl-diphenylamine
and their notable synergistic effect was observed. It was found that the anti-oxidation characteristics of the above-mentioned antioxidants were strongly affected by the composition of the corresponding base oil.