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PurposeTo study some tribochemical properties of tetrazole derivatives, n‐hexadecanyl (1H‐tetrazol‐1‐yl) acetate (HTA) and 1‐phenyl‐5‐(octylthio)‐tetrazole (PCT) as lubricating oil additives in hydrogenised oil, and estimate the action mechanism.Design/methodology/approach – The two tetrazole compounds were synthesized, and added them in hydrogenised oil with different concentrations. Their anti‐wear properties were evaluated with a four‐ball machine, the wear scar was analyzed with a X‐ray photoelectron spectroscopy (XPS).Findings – The novel compounds possess good anti‐wear, friction reduction properties and good load‐carrying capacity. According to the XPS results, the novel compounds were migrated onto the surface of the steel balls and adsorbed on the surface. The two additive compounds, themselves, and their decomposers contributed to the corresponding tribological performances. With S element contained in the compound PCT, the influence on the load‐carrying capacity of the base oil was enhanced. It may be due to the formation of S2− and SO42− compounds on the worn surface which could form a protective film.Research limitations/implications – Their antioxidant, anticorrosion, anti‐wear properties are not estimated.Practical implications – Two useful EP and AW lubricating oil additives were synthesized, and maybe it is the potential industrial applied lubricating oil additives.Originality/value – This paper provided a study way of some N‐containing heterocyclic compounds as lubricating oil additives.

PurposeThis paper sets out to study tribological properties, anticorrosive performances and thermal stabilities of two novel S‐N type triazinyl‐containing polysulfides {Bis[2,4‐bis(diethylamino)‐s‐triazin‐6‐yl] polysulfide (BBET‐PS) and Bis[2,4‐bis(di‐n‐butylamino)‐s‐triazin‐6‐yl] polysulfide (BBBT‐PS)} as additives in biodegradable grease, and to estimate the tribochemical mechanism.Design/methodology/approachExtreme pressure (EP) and anti‐wear (AW) properties of two compounds at different addition concentration were evaluated using a four‐ball machine. Their wear scar was analyzed with X‐ray photoelectron spectroscopy (XPS) and a scanning electron microscope.FindingsTwo novel S‐N type triazinyl‐containing polysulfides possess excellent load‐carrying capacity, good AW and show good corrosion‐inhibiting performance. The thermal stability of BBB‐PS is better than that of BBE‐PS. According to the XPS results, the triazinyl‐containing polysulfides react with the metal to generate a surface protective film consisting of sulfate, FeS and absorbed compounds containing organic‐N.Research limitations/implicationsThe antioxidant and biodegradability of the two novel compounds were not investigated.Practical implicationsTwo effective EP and AW additives were synthesized, and maybe potentially industrial applied lubricating grease additives.Originality/valueThe achievement of this study is the synthesis of two triazinyl‐containing polysulfides, which can be effective additives to improve the tribological performance of biodegradable grease.

A potentially good extreme‐pressure (EP) additive, diisobutyl polysulphide (PS‐i‐Bu), the main component of which is diisobutyl trisulphide, was synthesised at low temperature and under atmospheric pressure. Its load‐carrying capacity (PB and PD values) and antiwear and antifriction performance as an additive in a diester synthetic lubricant were investigated using four‐ball test machines, and compared with those for traditional sulphurised olefin (SO). Results show that the novel PS‐i‐Bu as an EP additive exhibits good load‐carrying capacity and antiwear properties. The load‐carrying capacity and antifriction performance of PS‐i‐Bu are better than those of the traditional SO; the antiwear performance of PS‐i‐Bu is slightly worse than that of the traditional SO. Scanning electron microscopy and X‐ray photoelectron spectroscopy data show that the PS‐i‐Bu additive undergoes similar tribochemical reactions to the traditional SO during the tribological process. The active element S in PS‐i‐Bu reacts with surface metal mainly to form FeSO4 and/or Fe2(SO4)3 inorganic films.

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