Friction reducing and antioxidant capabilities of engine oil additive systems under oxidative conditions

Neutral zinc(II) O,O‐di‐alkyldithiopho‐ sphates—variable temperature 31P NMR and quantum chemical study of the ZDDP monomer–dimer equilibrium

“…Current interest in ZDDP has included such topics as ligand exchange, [3,4] oxidation inhibition, [5] thermal film formation, [6] tribofilm formation, [7] antiwear properties, [8,9] friction properties, [10 -12] and interaction with other lubricating oil components. [13] Because of the need to replace ZDDPs partially or wholly by other phosphorus-free additives, [14] there is considerable interest in better understanding the chemistry of these materials.…”

Enhancement of Diarylamine Antioxidant Activity by Molybdenum Dithiocarbamates

“…Commonly employed sulfur-containing additives include molybdenum complexes, such as molybdenum dithocarbamates (MDTCs), which deposit a molybdenum disulfide (MoS 2 ) film upon continued exposure to elevated temperatures. − MDTCs and other organomolybdenum compounds have also been reported to have antioxidant activity. This is generally ascribed to their ability to decompose peroxides, − as has been shown for other metal dialkyldithiocarbamates. , MDTCs have been reported to lose their protective properties over time, which has been correlated to a decrease in their concentration throughout the course of oxidation. ,, As such, MDTCs rely on the action of hindered phenols and ADPAs with which they are typically blended in lubricants to prolong their antiwear ability over time. , Interestingly, MDTCs have been reported to extend the inhibition periods ascribed to ADPAs during the oxidation of lubricants. Guerret-Piécourt and co-workers, as well as Jianqiang et al, suggested that this synergism is due to the coordination of the N atom of the ADPA with molybdenum, stabilizing it to decomposition via sterics. , Later, Zhang and co-workers proposed that MDTCs increased the persistence of diarylaminyl and/or diarylnitroxide radicals formed in situ .…”

“…While phenolic RTAs generally trap 2 peroxyl radicalsthe first by HAT and the second by combination with the resultant phenoxyl radicalADPAs are capable of trapping far more owing to the reactivity of diarylnitroxide intermediates. In the so-called Korcek cycle (left cycle, Figure B), , the ADPA is regenerated from a diarylalkoxyamine formed from the combination of the diarylnitroxide with an alkyl radical. Since the diarylnitroxide must compete with O 2 for alkyl radicals, this mechanism can operate only when the concentration of the nitroxide is much greater than that of O 2 .…”

Base medium effect on the tribological behavior of oil‐water double soluble bismuth dithiophosphate

“…Their remarkable performance and reasonable cost‐effectiveness give rise to the strenuous efforts made by additive companies over the last decade to replace them, but without success. In order to make clear the nature and principle of ZDDP, the properties of reaction in solution, such as ligand exchange, peroxide decomposition, and thermal degradation were investigated (Handley and Dean, 1962; Jensen et al , 1998; Willermet et al , 1997; Hilgetag and Teichmann, 1965; Teichmann and Hilgetag, 1967). The chemical composition and formation of the tribochemical film with the functions of reducing friction and preventing wear were analyzed by applying extensively Auger electron spectroscopy X‐ray photoelectron spectroscopy (XPS), X‐ray absorption fine structure analysis, X‐ray absorption near‐edgy spectroscopy, X‐ray photoemission electron microscopy, second ion mass spectroscopy, and other surface analytical techniques during the current decade (Minfray et al , 2006; Pereira et al , 2006; Martin et al , 2001).…”