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The fast growing concern for maintaining integrity of the environment has built up development of environmentally‐adapted lubricants. Because of their toxicity, most of the traditional lubricating additives cannot be used in this kind of lubricant. The purpose of this paper is to find a borate ester derivative which can be used as a multifunctional additive in rapeseed oils (RSO).

A borated S‐2‐hydroxypropyl N, N‐dibutyl dithiocarbamate (BDTC) was synthesized and characterized. Its tribological properties in rapeseed oil as multifunctional additive were evaluated, using a four‐ball tribometer and compared with one kind of commercial MoDTC. In addition, its thermal stability was identified using TGA and antioxidative ability tested by PDSC. The action mechanism of BDTC was studied by X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atmospheric pressure chemical ionization mass spectrometer (APCI/MS) analysis.

Results show that BDTC exhibits high thermal stability, possesses comprehensive tribological performance in rapeseed oil, and has evident effect in controlling the oxidation of RSO. Analysis of worn surface indicates that BDTC was decomposed and reacted with metal during the friction process. The lubricating film mainly contains inorganic boron compound (B₂O₃), organic nitrogen derivatives and FeSO₄.

This paper provides a borate ester derivative which possesses excellent tribological properties and can be used as a multifunctional ashless additive in environmentally‐adapted lubricants. Furthermore, an innovative method, APCI/MS, was used to analyze the tribo‐fragmentation behavior of BDTC.

The purpose of this paper is to investigate the hydrolytic stability of several S‐hydroxyethyl N,N‐dialkyl dithiocarbamate‐derived borates SNB1, SNB2, and SNB3, to evaluate their tribological performances used as additives in polyalpha olefins (PAO), and to explore the tribochemical action mechanism.

First, the three additives are synthesized and characterized. Second, the hydrolytic stabilities of the three compounds are investigated. As the third step, they are, respectively, added to PAO and a series of samples with different concentrations of the additives in PAO are prepared, respectively. Their tribological properties are evaluated with two types of four‐ball machines, and then the wear scars were observed using a JSM‐5600LV scanning electron microscope. Finally, the elements on the worn surface are analyzed with a X‐ray photoelectron spectroscope (XPS).

The three novel compounds possess relatively good hydrolytic stabilities, excellent anti‐wear (AW) performances, friction reduction properties, and load‐carrying capacity. There is an optimum concentration of each of the three additives for their AW properties. According to the XPS analytical results, a boundary lubrication protective film has formed during friction consisting of FeSO₄ film, Fe₂O₃ film, and the complicated adsorption film composed of N‐containing organic compounds. In the protective films, a large quantity of compounds containing element B is not found.

The antioxidation performances and the anticorrosion properties are not estimated.

Three novel AW/extreme pressure (EP) additives are synthesized, and may be they have the potential industrial application as AW/EP additives in lubricating oil.

The present work provides a research method of N,S‐containing organic borates as lubricating oil additives.

The purpose of this paper is to examine the tribological behavior of the synthetic chlorine‐ and fluorine‐containing silicon oil as an aerospace lubricant.

The chlorinated‐phenyl and methyl terminated silicone oil (CPSO), chlorinated‐phenyl and trifluorinated‐propyl with methyl terminated silicone oil (FCPSO) were prepared. Their physical properties such as saturated vapor pressure and the evaporation weight loss were evaluated. The tribological properties of the silicon oils under moderate load were investigated with an Optimol SRV oscillating friction and wear tester, as well as Four‐ball friction and wear tester according to the standard method of ASTM D 4172 under higher load. The elemental composition generated on steel ball surface were analyzed on a scanning electron microscope with a Kevex energy dispersive X‐ray analyzer attachment (SEM/EDS), and the chemical nature of elements on worn surface lubricated with FCPSO were studied by X‐ray photoelectron spectrometer (XPS).

It is found that the CPSO and FCPSO show good tribological behavior for steel/CuSn alloy tribological pairs and are superior to hosphazene (X‐1P) and perfluoropolyether in terms of friction‐reduction ability and anti‐wear performance. The anti‐wear performance of FCPSO as lubricants for steel‐steel contacts is superior to CPSO. The EDS results showed existence of F and Si on the worn surface with lubrication of FCPSO, while XPS results indicated the occurrence of tribochemical reaction of FCPSO with friction pair during sliding process with the formation of FeCl₂, FeF₂ and the absorption silicon oil films on the lubricated metal surface.

The results substantiate that chemical reactive elemental such as chlorine or fluorine, which is substituted into silicon oil, helps to improve the anti‐wear and load‐carrying capacity of the liquid lubricant. So the excellent thermal stability, low‐temperature fluidity, very low‐saturated vapor pressure and excellent lubricity for steel/CuSn alloy of the silicon oil of FCPSO and CPSO make it an attractive alternative to conventional liquid lubricant for space mechanism.

In order to formulate ashless GL‐5 gear oils and high‐pressure antiwear hydraulic oils, the performances of extreme‐pressure (EP) and antiwear (AW), and the thermal and hydrolytic stability of series ashless P‐containing additives with different chemical structures are investigated by four‐ball EP test, high‐temperature oxidation test and hydrolytic stability test.Design/methodology/approach – Series ashless P‐containing EP and AW additives with different chemical structures were designed and selected, their EP and AW performances, high‐temperature oxidation, hydrolytic stability compared with the traditional zinc dialkyldithiophosphate (ZDDP) additive were investigated according to relative testing standards, and their applied performances compared with the traditional ZDDP additive were investigated using the CRC L‐37 gear oil rear axle test, Deniso T‐5D Vane Pump test and Deniso P‐46 Piston Pump test.Findings – The results indicate that two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability. The application performance of these P‐containing additives is also examined by CRC L‐37 rear axle test. The results show that only the oil samples with the addition of neutral thiophosphate esters correspondingly to API GL‐5 automotive gear oil can pass the CRC L‐37 gear oil rear axle test successfully. The results of further Deniso T‐5D Vane Pump and Deniso P‐46 Piston Pump tests prove that the ashless neutral thiophosphate ester is a very effective EP/AW additive for high‐pressure antiwear hydraulic oil. In one sentence, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP.Research limitations/implications – From the results, the neutral thiophosphate ester is the excellent ashless EP/AW additive and the useful substitute for ZDDP, however, their tribological mechanicsm and their synergic effect with the other additives used in the test base oil for the applied performance tests may be done in the future works.Practical implications – These results may be useful for the researchers to formulate some ashless high EP/AW industrial oils.Originality/value – This paper proves that the two ashless neutral thiophosphate esters exhibit excellent EP and AW performances, high‐temperature oxidation and hydrolytic stability, and is the useful substitute for ZDDP for formulating ashless GL‐5 gear oils and high‐pressure AW hydraulic oils.

In order to develop novel high EP S‐containing additives and to meet the need of formulating GL‐5 gear oil or other high EP lubricating oils, aims to investigate the tribological behaviors and mechanism of a di(iso‐butyl)polysulfide (DIBPS), which was synthesized from some cheap materials at low temperature and under normal atmospheric pressure, as an additive in some mineral base oils compared with the traditional sulfurized olefin (SO) additive.

The DIBPS additive was designed and synthesized, of which the main composition is the di(iso‐butyl)trisulfide. Its load‐carrying capacity, anti‐wear and friction reduction properties as additive in some mineral base oils, compared with the traditional SO additive, were investigated using a four‐ball machine and a Timken tester according to relative testing standards. The tribological mechanism was discussed according to the SEM and XPS analytical data.

The results indicate that the four‐ball P_D value and the Timken OK value of the prepared DIBPS in VHVIS500 is clearly better than that of the traditional SO; the anti‐wear property of DIBPS is equivalent to the traditional SO and the friction reduction effect of DIBPS is better than that of the traditional SO. The SEM and XPS data show that the DIBPS additive experiences different tribochemical reaction during tribological process compared with the traditional SO. The S active element of DIBPS reacted with surface metal mainly to form FeSO₄ and/or Fe₂(SO₄)₃ inorganic film, but the S active element of the traditional SO reacted with the surface metal mainly to form FeS inorganic film. This may be the chief reason why the prepared DIBPS possesses better EP properties than the SO.

The results show that the polysulfide additive (DIBPS) possesses better extreme pressure property than the traditional SO. However, more experimental study such as the synergic effect with other additives must be performed, from which it will be clearly shown whether the novel polysulfide can be applied in industrial oils.

These results may be useful for the researchers to formulate some high EP industrial oils.

This paper proves that the designed polysulfide additive, of which the main composition is the trisulfide, possesses better extreme pressure property than the traditional SO, and its tribological mechanicsm is also different with that of SO. It is noticed that the preparative method of this novel polysulfide additive has some superiorities, such as: low‐experimental temperature, low‐experimental pressure and cheap materials.

The purpose of this paper is to study the tribological properties of a thiazole derivatives (T561), overbased alkyl benzene calcium sulfonate (T106A) compounded with T561 and overbased alkyl benzene magnesium sulfonate (T107) compounded with T561 in rapeseed oil (RSO).

A four-ball machine was used to evaluate the tribological properties of each compound and their combinations with T561 in RSO. Scanning electron microscopy, EDX and X-ray photoelectron spectroscopy were applied to analyze the tribofilm formed on the worn surfaces.

Results of tribotesting demonstrated that synergistic effects exist between the overbased sulfonates, T106A and T107, and the thiazole derivative, T561. The texts of tribofilm indicated that iron sulfide and iron oxides exist in T561 single agent lubricant film and two composite additives lubricant film, and no sulfates were detected. It suggested that the addition of alkyl benzene sulfonate did not hinder the formation of iron sulfides and iron oxides. Meanwhile, CaSO₄ (MgSO₄) and CaCO₃ (MgCO₃) were detected on the worn surface of the composite additives, which were not detected on the single agent friction surface.

A tribofilm mainly contains CaSO₄ (MgSO₄) and CaCO₃ (MgCO₃) formed on the worn surfaces, which is responsible for excellent extreme pressure and anti-wear properties of the compound agents because of their high melting point and high shear stress.