Synthesis And Tribological Properties Of New Type Sulfur-and Phosphorus-free Organic Molybdenum Additives

The issues of environment and energy sources have become international hotspots nowadays. And, environment regulations have been introduced to restrict the permissible level of phosphorus and sulphur (PS) because these can poison the catalysts that are used to remove pollutants from engine exhaust gas. These restrictions are leading to the development of low or zero PS additives which necessitate a reduction in the level of ZDDP employed in crankcase oils. So far, considerable study has been made by research institutions and additive companies to replace ZDDPs by another highly cost-effective compound, but the efforts have proved of little avail.Molybdenum is well known for its lamella-layered structure and low-shear strength that provide excellent friction reduction characteristics in high-pressure contacts. In this study five kinds of water-soluble molybdenum-containing substitutes (WMCS) and two kinds of oil-soluble molybdenum-containing substitutes (OMCS) were synthesized by means of chemical reactions between a molybdenum source and a fatty acid salt of ethanol amine, and then characterized by FT-IR.The four ball test results showed that all WMCS had obvious beneficial effect on the improvement of water lubricity; the results of end-face friction and wear tester on the steel/aluminum and steel/red copper friction pairs show that the WMCS have good impact on reducing the friction coefficient and wear; the results of fatigue test show that WMCS have good anti- fatigue properties. Thereof, a5 has the best over-all properties.The four-ball tribotest results exhibited that the carrying capacity of b1, b2 is worse than that of ZDDP and MoDTP, but the friction-reduction and antiwear of b1, b2 are better. There into the average friction coefficient and WSD of b1 with concentration of 3.0% are the lowest of all, which are lower than 150SN base oil up to 51%, 48% respectively. What's more, the SP-free organic molybdenum compounds can exhibit good antiwear and friction- reducing synergism with ZDDP.The mechanism of extreme-pressure,antiwear and friction-reducing by these SP- free organic molybdenum compounds have also been discussed,showing that on the rubbing surface a protective film consisting of a reaction layer (FeO, Fe2O3 and FeOOH), a complicated organic nitrogen adsorption film and a sediment film MoO3 was formed as a result of decomposition of SP- free organic molybdenum.