Tribological Behaviors of S, B-Containing Morpholine Derivatives as Additives in Rapeseed Oil

Two novel ashless and non-phosphorus S, B-containing morpholine derivatives, MBOC and MBOD, were prepared and their tribological behaviors in rapeseed oil (RSO) were evaluated using a four-ball tester. Thermal degradation tests were conducted to identify their thermal stabilities using a thermo-gravimetric analyzer. The worn surfaces of the steel balls were investigated by scanning electron microscopy (SEM). The results indicated that the additives possessed high thermal stabilities and good load-carrying capacities. Moreover, they both had good anti-wear and friction reducing property at a relatively high concentration (1.5 m%) and under all test loads. The results of XPS analyses illustrated that the prepared compounds as additives in RSO could form a protective film containing inorganic sulfide, sulfate, oxidized compounds and organic nitrogen-containing compounds on the metal surface during the sliding process.