molybdenum dithiocarbamate is a friction-reducing additive containing both inorganic and organic components. It consists of a bridged or mono-nuclear molybdenum core with dithiocarbamic acid and contains several alkyl groups. It has been reported that it acts as a catalyst in the formation of low-friction MoS2 (tribofilm) on rubbed surfaces. A tribometer equipped with Raman spectroscopy was used to monitor changes in the chemical composition of the tribofilm, and to examine the effects of shear stress and temperature on the MoS2 film formation.
A novel molybdenum dialkyldithiocarbamate, prepared from asymmetric dialkylamines, has been synthesized and found to be more effective in reducing friction than a known symmetrical compound of this type, molybdenum dialkyldithiophosphate. The compound is soluble in petroleum slack oil, and lubricating compositions containing the molybdenum dialkyldithiocarbamate exhibit good friction reduction and tribological performance.
Lubricating compositions based on the novel molybdenum dialkyldithiocarbamate may be formulated with zinc salts to provide antiwear and extreme pressure protection. Preferred zinc salts include the dibutyl hydrogen phosphite and triphenyl monothiophosphate, as well as the thiocarbamate ester formed by reacting dibutyl amine, carbon disulfide and the methyl ester of acrylic acid.
The friction and wear behavior of two important additives for boundary lubrication, ZnDDP and Molybdenum dialkyldithiocarbamate (MoDTC), were examined in reciprocating sliding contact with ball-on-reciprocating plate test equipment, in squalane of a pure hydrocarbon oil. Tribofilms were monitored by Raman spectroscopy, and the chemical structure of the tribofilms was characterized by Energy Dispersive X-Ray analysis and X-ray photoelectron spectroscopy.