Interfacial Antiwear and Physicochemical Properties of Alkylborate-dithiophosphates
2011 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, Vol. 3, no 4, 956-968 p.Article in journal (Refereed) Published
Boron compounds have become of interest in tribology because of their unique tribochemical and tribological properties. At the same time, dialkyldithiophosphates (DTPs) of transition metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Because of the environmental pollution and health hazards of these compounds, ashless compounds with reduced amounts of sulfur and phosphorus are desirable. This work reports on the synthesis, characterization, and tribological properties of a new class of compounds, alkylborate-dithiophosphates. This class combines two high-iron-affinity surface active groups, borate and dialkyldithiophosphate, into a single molecule. The final products, viscous liquids, were characterized by FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Residues of one representative compound from this class, DPB-EDTP, after thermal analyses were additionally characterized by multinuclear 13C, 31P and 11B MAS and 31P CP/MAS NMR spectroscopy. Solid-state NMR data suggest that a dominant part of the solid residue of DPB-EDTP consists of borophosphates. Antiwear and friction properties of a mineral oil with these novel additives were evaluated in a four-ball tribometer in comparison with O,O?-di-n-butyl-dithiophosphato-zinc(II), Zn-BuDTP, as a reference lubricant additive. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy-dispersive X-rays spectroscopy (SEM/EDS). The results show that alkylborate-dithiophosphates, with substantially reduced amounts of sulfur and phosphorus compared with Zn-BuDTP, have considerably better antiwear and friction performance.
Place, publisher, year, edition, pages
2011. Vol. 3, no 4, 956-968 p.
dialkylborate-alkyl-dialkyldithiophosphates, lubricant additives, Zn-BuDTP, thermal analyses, borophosphates, solid-state MAS NMR, SEM/EDS
IdentifiersURN: urn:nbn:se:kth:diva-79860DOI: 10.1021/am101203tISI: 000289762400007OAI: oai:DiVA.org:kth-79860DiVA: diva2:495771
QC 201202102012-02-092012-02-092012-02-10Bibliographically approved