In addition, it is reported that alkyl diphenylamine, carbamate and molybdenum salts are used together for lubricating oil, which can pass the related bench test. Domestic researchers believe that molybdate and aryl amine compounds can produce some compounds with better antioxidant properties, thus enhancing the stability of aryl amine antioxidants. As a result of this action, the reaction ability of aryl amine is decreased, thus increasing its oxidation induction period. With the implementation of gF-5 specification of car engine oil, the limit of sulfur and phosphorus content in engine oil will be more stringent, and higher requirements will be put forward for antioxidant, anti-wear and anti-friction performance of oil products. Against this background, the anti-wear and anti-friction properties of non-thiophosphorous molybdate and borate additives as well as their antioxidant synergies with amine antioxidants will undoubtedly become a bright spot in the research of engine oil additive formulations. N- phenyl - - naphthylamine compounds have good antioxidant effect at high temperature. Phenyl - - naphthylamine has better antioxidant effect than diphenylamine, but it is easy to produce precipitation. Phenolic antioxidants, phenyl - -naphthylamine and diphenylamine combined, not only the induction period is significantly increased, but also the residue amount is reduced a lot, so phenyl - -naphthylamine is generally combined with other additives. In aviation lubricating oil, N - phenyl - alpha - naphthylamine is indispensable component in the composite antioxidant, and diphenylamine compound use antioxidant, can show excellent oxidation resistance, such as the MIL - L - 7808 - j contains L % of aviation lubricating oil, to '- two isooctyl diphenylamine and 1.2% of N - phenyl - alpha - naphthylamine and MIL - L - 23699 aviation lubricating oil containing 0.6% of N - phenyl - alpha - naphthylamine and 1.1% for, for' - two isooctyl diphenylamine. Yanjier's study showed that phenyl - -naphthylamine was an antioxidant with strong compatibility, and the combination of phenyl - -naphthylamine and ZDDP had excellent antioxidant performance. Phenothiazine, also known as diphenylamine sulfide, belongs to the diphenylamine antioxidants, its antioxidant effect is better than diphenylamine, because it is both free radical scavengers and peroxide decomposition agents.
Phenothiazine has been used in aero-engine lubricants since the 1950s, and is characterized by its effectiveness in suppressing the increase in viscosity following high temperature oxidation of the oil, but its disadvantage is that it is highly greasy. It has been suggested that adding long carbon chain alkyl to benzene ring or nitrogen atom can increase the oil solubility of phenothiazine and thus reduce the formation of sludge. Since the early 1990s, research into the use of phenothiazine derivatives in internal combustion engine oils has increased, mainly due to increased engine efficiency, which increases the operating temperature of internal combustion engine oils, while environmental requirements reduce the use of ZDDP, requiring more efficient high temperature antioxidants. In recent years, the applications of phenothiazine derivatives in internal combustion engine oils have been reported, and the applications of phenothiazine derivatives in refrigerant oils have been studied. With the increasing requirement of energy saving, the efficiency and thermal load of mechanical equipment increase, and the corresponding requirement of lubricating oil with better high-temperature oxidation resistance performance, and alkyl phenothiazine is a high temperature antioxidant that has been studied more in recent years abroad. There are two main types of alkyl phenothiazines: phenothiazines that are alkyl-substituted on nitrogen atoms and alkyl-substituted on benzene rings, which are more commonly used in lubricants.