bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of molecular structure of organic borates on their friction and wear properties
Authors: Liu Weimin , Xue Qunji , Zhang Xushou , Wang Hanqing
Published: July 2006

Six organic borates of different molecular chain length were synthesised, and the friction and wear properties of these borates as oil additives were evaluated using a Timken Tester. X‐ray photoelectron Spectroscopy (XPS) was used to study the surface composition and valence state of boron on the rubbed surfaces.

It was found that the antiwear and friction reduction effects of the borates are significantly influenced by the molecular chain length. The longer the chain length, the lower the friction coefficient and wear, and the higher the failure load. XPS analyses of rubbed surfaces revealed that the binding energy of BIS increased after rubbing, but no pure B(OH)3 and B2O3 was generated. the load‐carrying capacity and the antiwear effect are probably related to the ratio of numbers of carbon atoms to numbers of boron atoms on the rubbed surfaces.
Importance of anionic reactive intermediates for lubricant component reactions with friction surfaces
Authors: Kajdas Czeslaw
Published: July 2006

To understand the chemical behaviour of lubricant components during boundary lubrication, a general concept of negative ionradical reactive intermediates formation for these components has been proposed. The concept is based upon the ionisation mechanism of these compounds caused by the action of electrons of law energy (1–4 eV). Electrons of such energy (exoelectrons) are spontaneously emitted from most fresh surfaces formed during friction. The principal thesis of the model is that lubricant components form anions which are then chemisorbed on the positively charged areas of rubbing surfaces.

The formation of negative ions and their decomposition process are simulated by electron attachment mass spectrography. This type of mass spectrography uses electrons of an energy range similar to those of exoelectrons. The proposed model encompasses the following major stages: (a) low‐energy electron emission process and creation of positively charged spots, (b) action of emitted electrons with lubricant components (anion and radical formation), (c) reactions of anions with metal surfaces forming a film protecting the surface from wear, (d) cracking of chemical bonds producing other radicals. The model explains many lubrication phenomena of hydrocarbons, oxygen‐containing compounds, and many types of chemicals used as antiwear and extreme‐pressure additives.
Succinimide phosphoric acid esters as multipurpose additives
Authors: Naga H. H. Abou El , Mohamed M. M. , El Meneir M. F.
Published: July 2006

Succinimide phosphoric acid esters have been synthesised and evaluated as antioxidants and ashless dispersant additives for crankcase lubricating oils. The synthesis is based on reacting succinimides (as prepared by the reaction of polyisobutylene, maleic anhydride and tetraethylene pentamine) with phosphorus pentoxide in the presence of alcohols with different carbon numbers Results showed that the magnitude of the oils' oxidation stability, as well as their dispersive power, are both highly related to the chemical structure of the alcohol used.
Computer simulation of turbine oil oxidation. 2: Consumption of a hindered phenol antioxidant in laboratory oxidation tests and in service
Authors: Igarashi Jinichi , Yoshida Toshio
Published: July 2006

The computer simulation study of consumption of di‐tert‐butyl p‐cresol (DBPC) was extended to the oxidation of hexadecane/tetralin model oils under conditions of laboratory oxidation tests and in service. The oxidation lives of the model oils in the ALCOA oxidation test and the ASTM D2272 rotary bomb and D943 turbine oil oxidation tests were successfully predicted from the simulation study. The oxidation behaviour of the model oils is compared to that of a turbine oil used in actual service units. The model oil having 6 mass % of tetralin showed almost identical oxidation behaviour to the turbine oil when the same amount of DBPC was added (0.6 mass %). The calculation shows that the direct oxidation of antioxidants is the main process of antioxidant consumption in the laboratory oxidation tests as well as in the model oxidation system without metal catalysts. In most of the service units which operated at moderate conditions the calculation shows that the direct oxidation of antioxidants is also the main, process. As a consequence, the rate of antioxidant consumption does not depend much on the tetralin content in the model oils. The oxidation behaviour of the model oils in the service units which operate under severe conditions, such as in the high temperature regions of turbines, is calculated by setting a flow reactor model. The results of this calculation show in this case that the turbine oil degradation occurs mostly in the high temperature regions and that the rate of antioxidant consumption increases with an increased amount of tetralin in the model oils. This strong dependence on base oil composition can be attributed to the increased importance of antioxidant consumption through the inhibition of oxidation.
Laboratory screening tests for low sulphur diesel fuel lubricity
Authors: Cooper D.
Published: July 2006

Since the beginning of October 1993, environmental legislation in the USA has required the sulphur content of diesel fuel to be reduced to less than 0.05 wt.% for road vehicles. Pressure for such reductions to be adopted in other markets is growing: notably, sulphur levels as low as 10 ppm are being encouraged in Sweden by the use of tax incentives. However, it is suspected that fuel pumps suffer from lubrication problems with the use of low sulphur diesel (LSD). Additive treatment of fuels and fuel blending is thought to mitigate such problems but there is a need for an industrial method of screening candidate fuel treatments prior to expensive service or rig trials.

This paper outlines a test procedure based on the Plint TE‐77 reciprocating test rig. Initial investigations have enabled fuels of known pump performance to be ranked correctly through an assessment of scuffing wear. In this test, scuffing is evaluated by surface profilometry of the flat specimen and the mechanism is verified by the detection of ‘white’ etching layers on surfaces. The test also allows the separate evaluation of mild wear by measurement of the width of the scar generated on the roller by the line contact configuration.
A study of alkylthiomethylbenzotriazoles as multifunctional lubricating oil additives
Authors: Ren Tianhui , Wan Yong , Xue Qunji , Wang Hanqing
Published: July 2006

Three new oil‐soluble alkylthiomethylbenzotriazoles were synthesised with the reaction of 1‐chloromethylbenzotriazole and sodium alkyl mercaptan in iso‐propanol at room temperature for 12 h. Their load‐carrying capacity and friction and wear properties when added to liquid paraffin were then evaluated using a Seta‐shell four‐ball machine. Their thermal stability in static air was examined by DSC analysis, and their friction reduction and antiwear mechanisms were investigated using XPS and AES analysis.
Functional mechanism of formation of friction polymer with dihydroxydocosanoic acid
Authors: Hu Zhimeng , Tao Dehua , Wang Ru‐Lin
Published: July 2006

The results of wear tests with a four‐ball machine showed that dihydroxydocosanoic acid has good antiwear properties, comparatively approaching those of zinc dialkyldithiophosphate (ZDDP): the four‐ball wear‐scar diameters, d 30 min/294 N, with dihydroxydocosanoic acid, ZDDP, and 400 neutral base oil are 0.36, 0.35, and 0.62 mm, respectively. In order of effectiveness the antiwear ability of the C22 acids is: 13,14‐dihydroxydo‐cosanoic acid (I) 13(14)‐mono‐hydroxydocosanoic acid (II) docosanoic acid (III), showing that their antiwear properties are remarkably improved after introduction of the hydroxy group into fatty acids. Work on dihydroxy acid as an antiwear agent is not much reported in the literature up to now. In the present work, it was verified with infrared spectroscopy that polyester is formed on the rubbing surfaces with I and II by tribochemical reaction. An oxygen‐rich protective film on the rubbing surfaces was identified with Auger Electron Spectroscopy analysis. These results are identical to the high oxygen‐containing polyester film shown by IR analysis. It is preliminarily confirmed that the functional antiwear mechanism is, principally, the formation of a polymeric friction film on the rubbing surfaces.
Seizure resistance of phosphated coatings: Influence of carbon content and metallurgical structure of plain carbon steels
Authors: Adjerid S. , Hivart H. P. , Bricout J.‐P. , Oudin J. , Traisnel M.
Published: July 2006

Variables which affect the seizure resistance of zinc phosphate coatings on steel, as used in cold forging, are studied by considering the influence of carbon content and metallurgical structure of a set of plain carbon steels. A seizure test, that is particularly well suited to evaluating the mechanical strength of phosphate‐stearate coatings, has been previously developed by the authors. Test results based on seizure occurrence are related to the effective phosphate bonding and to lubricant reactive effects. The results obtained show that seizure resistance of annealed plain carbon steel is optimal for carbon contents in the range of 0.38 ˜ 0.48% C. In this case, the phosphate structure is very fine and very dense, and consists of mixed needle and block crystals. Phosphate coating weight is also higher. The studies of metallurgical structures of steel show that highest seizure resistance is obtained for spheroidised structure. In this case, the phosphate coating weight is low and cannot be taken into account in characterising the efficiency of the phosphate coating.
Lubrication modes and the IRG transition diagram
Authors: Schipper D. J. , De Gee A. W. J.
Published: July 2006

The relationship between a Lubrication Mode Diagram (LMD) for concentrated contacts (LCC's) and the ‘IRG transition’ diagram has been studied. In addition, scuffing results, obtained by the IRG (International Research Group) have been analysed, as well as the results of scuffing tests performed by different workers using a two‐disc apparatus.

It has been found that in Region I of the IRG transition diagram, three sub‐regions can be distinguished, representing elastohydrodynamic lubrication, mixed lubrication, and boundary lubrication, respectively. Thus, the IRG transition diagram is not comparable to a ‘lubrication mode diagram’. Furthermore, it has been found that failure of LCC's by scuffing most frequently occurs under conditions of mixed lubrication. Therefore, scuffing criteria based upon the assumption that the load at failure is carried entirely by the micro‐contacts are doubtful, and probably wrong.
An evaluation of antioxidants for vegetable oils at elevated temperatures
Authors: Becker R. , Knorr A.
Published: July 2006

The antioxidant efficacy of various oxidation inhibitors in low erucic acid rapeseed oil has been studied in a screening test at 130°C by an induction period method. Hindered monophenols, sulphides, phosphites, aromatic amines and zinc dithiophosphates yielded no or only marginal stabilising effects. Remarkably increased oxidation stabilities were observed with certain hindered bisphenols, polyhydroxybenzenes, zinc and bismuth dithiocarbamates. In high oleic sunflower oil with a lesser portion of multiple unsaturation, these additives induced relatively longer induction periods. Mixtures of zinc dithiocarbamates and 4,4′‐methylenebis‐(2, 6‐di‐tert‐butylphenol) or octylated di‐phenylamine, as well as compositions of all three compounds, exhibited synergistic effects. Under the conditions employed these additives were distinctly superior to commercially recommended formulations. A mechanistic concept of the antioxidant action of zinc dithiocarbamate is briefly discussed.
Study of deposit and friction films of overbased calcium sulphonate by PM‐IRRAS spectroscopy
Authors: Palermo T. , Giasson S. , Buffeteau T. , Desbat B. , Turlet J. M.
Published: July 2006

This paper deals with the study of deposit and friction films of overbased calcium sulphonate diluted in mineral oil, on metal surfaces.

The technique used for this work is Infrared Reflection Absorption Spectroscopy by Fourier Transform and Polarisation Modulation (PM‐IRRAS or PM FTIR). The spectra obtained from this method contain only information on the absorption occurring in the immediate neighbourhood (⩽40 nm) of the metallic substrate and allow the average orientation for molecules adsorbed on metals to be deduced.

This study shows that the adsorption of overbased calcium sulphonate on a steel surface leads to a preferential orientation of the sulphonate chains perpendicular to the surface and to a preferential orientation of the carbonate, the c axis being perpendicular to the surface. During friction, the sulphonate chains are ejected from the contact zone. We observed that the boundary film consists mainly of calcium carbonate, which crystallises into calcite.
Human health and environmental hazard characterisation of lubricating oil additives
Authors: Michael Cisson C. , Rausina Gary A. , Stonebraker Peter M.
Published: July 2006

The authors' company has characterised the potential human health and environmental hazards of widely used classes of lubricating oil additives and polyalphaolefin (PAO) base fluids in a battery of toxicity tests. The main classes of additives are: succinimide ashless dispersants, calcium sulphonates, calcium phenates, zinc dialkyldithiophosphates, oxidation inhibitors, and antiwear inhibitors. In summary, mammalian toxicity studies indicate that lubricant additives do not pose a significant health risk to humans. Ecotoxicity is also considered to be of low concern in general. Even though lubricant additives do not readily biodegrade, studies are under way to confirm that they are not persistent in the environment and that bioaccumulation is not a concern. Good Laboratory Practice (GLP) methods have been developed for analysis of additives involved in toxicity tests and for low concentrations (ppb) of additives in aqueous systems. Manufacturing advances are reducing the release of toxic by‐products to the environment.
On the theory of time‐dependent micro‐TEHL for a non‐Newtonian lubricant in line contacts
Authors: Yang  , Peiranm  , Shen  , Jiankun
Published: July 2006

This paper presents a relatively complete numerical solution to time‐dependent micro‐thermoelastohydrodynamic lubrication in line contacts subjected to constant load and entraining velocity. Sinusoidal functions are employed to model the traverse roughness on contact surfaces. The Eyring model is used to describe the non‐Newtonian flow of the lubricant. With respect to time, the problem is treated as a periodic one so that most variables, such as pressure, film thickness and temperature, can be considered as periodic functions. An efficient algorithm is developed, and a number of cases are solved. The results indicate that the lubricant squeeze induced by the motion and interaction of rough surfaces significantly affects the solution of micro‐thermoelastohydrodynamic lubrication.
A graphite intercalation compound additive in oil
Authors: Jun Tian , Qunji Xue
Published: July 2006

A third‐stage FeCl3‐graphite intercalation compound (GIC) with flake graphite has been synthesised by a solvent method. The FeCl3 deintercalation of GIC forms thick complex film on the metal surface during the friction process, which increases the extreme pressure qualities of the paraffin liquid.
Elastohydrodynamics of the rotary lip seal
Authors: Salant Richard F.
Published: July 2006

An elastohydrodynamic model of the non‐leaking equilibrium behaviour of the rotary lip seal has been developed. It consists of a fluid mechanics analysis of the lubricating film, a structural analysis of the lip, an analysis of the meniscus on the air side of the seal, and an iterative computation procedure. A uniform distribution of microasperities on the lip surface is assumed. The model predicts the location of the meniscus, the film thickness and pressure distributions, and the locations of cavitation regions. It also predicts the maximum pressure that can be sealed with zero leakage, and the maximum speed above which the meniscus is ingested into the sealing zone.
Mixed lubrication — an overview
Authors: Spikes H. A.
Published: July 2006

The regime known as ‘mixed’ lubrication lies between those of hydrodynamic and elastohydrodynamic. This paper reviews work on this subject, in order to recognise the key areas of progress, and of ignorance. Film thickness and surface roughness are discussed, to conclude that below certain values of λ, there are limitations to earlier models. Computational solution of the micro‐EHD problem has largely succeeded, as well as more analytical approaches. The mixed lubrication regime has been studied by electrical contact resistance, friction measurement, and, more recently, analysis has been aided by optical interferometry — the implications of this work, and future prospects, are addressed.
Tribological behaviour of the adduct of bis(O,O′‐dibutyldithiophosphato)‐nickel (II) with isoquinoline
Authors: Bao‐Ling Song , Ren‐Gen Xiong , Jun‐Xiu Dong , Xiac‐Zeng You
Published: July 2006

The bis(isoquinoline) adduct of bis(O,O′‐dibutyldithiophos‐phato)nickel (II), Ni(dtp)2 · 2IQ, has been prepared; its crystal structure reveals that the nickel atom is bonded to four sulphur atoms of the dithiophosphate molecule, and two nitrogen atoms in the isoquinoline ring, to form a six‐coordinated complex. Evaluation of the adduct's properties as an extreme‐pressure (EP) and antiwear (AW) additive was conducted using a fourball machine. The results show that Ni(dtp)2 · 2IQ exhibits better load‐carrying capacity than Ni(dtp)2 and Zn(dtp)2, but poorer antiwear abilities. SEMs show that a wear scar surface on the ball lubricated with the adduct was much rougher than for those with isooctanol, Ni(dtp)2 and Zn(dtp)2, respectively. Further, energy dispersive X‐ray (EDX) spectra indicates that the sulphur concentration in the wear scar lubricated with the adduct is much less than that of Ni(dtp)2, which leads to a lesser wear reducing ability.
Changes in the mechanical properties of oil used in a gasoline engine
Authors: Kang Suckchoon
Published: July 2006

This study is concerned with the changes in and deterioration of the mechanical properties of oil used in a gasoline engine. The properties analysed were friction and antiwear performance, wear debris, load‐carrying ability and the formation of surface films.

It was found that the oil run in an engine deteriorated so as to increase the wear and friction and decrease the load‐carrying ability as the running distance of oil was increased. The main cause of deterioration was related to the ability to form a protective film in the contact zone. When the film was produced by additives (sulphur), this could properly protect the surface in the contact zone undepleted from wear and friction. But as the oil deteriorated, it could not form such a film and so its protective ability on sliding surfaces diminished.
Tribological aspects of by‐pass oil filters on gasoline passenger car engines
Authors: Daniel Klaus
Published: July 2006

Contaminants in passenger car engines are physically separated from lubricating oil by full flow oil filters. The additional cleaning in by‐pass filters should allow oil drain intervals to be extended or to operate engines without oil change and reduce engine wear noticeably, as claimed by some by‐pass filter manufacturers.

To establish whether the claim is mere conjecture or if the addition of by‐pass filters into the oil circuits of passenger car gasoline engines are indeed of real benefit with respect to engine and lubricant performance, a research project was initiated by the UBA on behalf of the German environment ministry.

Special attention had to be paid to the influence on oil contamination, variation in viscosity, detergency, dispersancy, fuel and oil consumption, engine wear and overall reliability and durability. Some highlights of the total programme are presented in this paper.
Effect of metallic thiophosphates on dropping point and penetration properties of some greases
Authors: Mittal B. D. , Sayanna E. , Naithani K. P. , Rai M. M. , Bhatnagar A. K.
Published: July 2006

Thiophosphates of zinc and molybdenum have been used in lubricant formulations to impart extreme pressure and anti‐wear properties for some time. Zinc dialkyldithiophosphate has found favour in greases as a multifunctional ‐ antioxidant, extreme pressure and antiwear ‐ additive.
The effect of basic nitrogen compounds on the tribological performance of sulphurised olefin
Authors: Yulin Qiao , Binshi Xu , Shining Ma , Weimin Liu , Qunji Xue
Published: July 2006

The effect of the molecular structure of basic nitrogen compounds on the lubricating properties of sulphurised olefin has been investigated using a Timken tester. X‐ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X‐ray Analysis (EDAX) were used to study the chemical states of sulphur and nitrogen on the rubbed surfaces and the reaction rates of sulphur and iron separately. It was found that the antiwear and friction reduction properties of sulphurised olefin are greatly influenced by the different molecular structures of the basic nitrogen compounds. A composite additive package containing basic nitrogen compounds with sulphurised olefin can produce either synergistic or antagonistic effects, due to the influence of the different molecular structures of the basic nitrogen compounds. XPS analysis revealed that a tribochemical protective film containing nitrogen and sulphur was formed on the rubbed surface. EDAX analysis indicated that the reaction rates between elemental sulphur and iron were influenced by the different molecular structures of the basic nitrogen compounds. It was found that the apparent reaction rates of elemental sulphur and iron are related to the tribological characteristics of the additive package.
molecular spectroscopic studies of ZDDP—PIBS interactions
Authors: Kapur G. S. , Chopra Anju , Ramakumar S. S. V. , Sarpal A. S.
Published: July 2006

The effect of the nature and alkyl chain length of zinc dialkyldithiophosphate (ZDDP) (R = C4 to C8) on its interactions with polyisobutenyl succinimide (PIBS) has been investigated using 31P‐NMR and infrared spectroscopy. 31P‐NMR spectra of ZDDP in the presence of PIBS showed both broad (35–850 Hz) and sharp (50–100 Hz) resonance signals due to different modes of interaction, mainly cluster formation and specific complexation, respectively. Single‐ended mono‐PIBS exhibit stronger interactions compared to the double‐ended bis‐PIBS. The proportion of sharp signals due to specific complexes in 31P‐NMR spectra of ZDDP—PIBS blends are in the order: C8 > C5 > C4+C8 > C6 = aryl ZDDP. The effect of PIBS concentration on the strength of complexes has also been studied.
Synthesis and characterisation of an effective N‐containing zinc diaryl‐dialkyldithiophosphate additive by mannich reaction
Authors: Hu X. , Yuan G. , Zhou Z.
Published: July 2006

This paper reports on the synthesis and tribological performance of N‐ZDDP, a type of additive containing nitrogen, that is O,O‐diaryl‐N‐methylene‐O,O‐zinc dialkyldithiophosphate, synthesised by Mannich and other reactions, and useful for improving antioxidation and anticorrosion behaviour in hydraulic, gear, and engine oils. Compared with conventional zinc dialkyldithiophosphate (ZDDP), N‐ZDDP widens the thermal decomposition temperature range, and its antioxidant behaviour is improved by 40%, and its anticorrosion properties by 50%. The load‐carrying capacity of N‐ZDDP is superior to that of ZDDP; its wear resistance, however, is similar to that of ZDDP.
Relationship between the properties of polyisobutenyl succinic anhydrides and their additive derivatives
Authors: Hancsók J. , Bartha L. , Baladincz J. , Kocsis Z.
Published: July 2006

Engine oils today include detergency dispersancy additives to keep the engine clean, hold insolubles in dispersion, and neutralise acidic compounds.

This paper describes the synthesis of a type of detergent‐dispersant based on polyisobutenyl succinimides. The type and route of synthesis influence the molecular structure, performance, and applicability of the synthesised compounds. In particular, the average molecular weight of the polyolefin chain of the intermediates used has a decisive effect. A newly developed intermediate allows the preparation of polysuccinimides with a polymeric structure.
Synthesis and tribology of aluminium hexoxylborate as an antiwear additive in lubricating oil
Authors: Hu Z. S. , Dong J. X. , Chen G. X.
Published: July 2006

An oil‐soluble compound containing aluminium and boron has been synthesized. The tribological properties of the compound in SN500 oil were evaluated on a four‐ball and block‐on‐ring test apparatus. The results showed that the wear resistance and load‐carrying capacity of the oil were improved, and the friction coefficient was decreased. Evidence of deposition was found in the wear scar by SEM. It is concluded that this deposition provided the oil with its good wear resistance properties.
A study of thermal and lubrication phenomena in the piston‐ring and cylinder‐sleeve tribosystem of an internal combustion engine and flash temperature calculation
Authors: Manolache Gh. , Cretu Sp. , Olaru D. N. , Bujoreanu C. G.
Published: July 2006

The piston ring is one of the main elements in an internal combustion engine. Together with the cylinder sleeve, the piston ring has two basic functions: (1) contacting the cylinder sleeve to prevent the gases formed above the piston from migrating to the crankcase and (2) as a translation couple, formed of the piston‐ring and cylinder‐sleeve assembly.

Complex tribological phenomena occur in the piston‐ring and cylinder‐sleeve tribosystem, according to variations in sliding speed, gas pressure, and temperature.

This paper presents a method of calculation of the thickness of the lubricant film in the piston‐ring and cylinder‐sleeve tribosystem, using the Reynolds equation, integrated in specific conditions. According to the Newtonian behaviour of the lubricant, the shear stresses in the lubricant film between the piston ring and cylinder sleeve are determined. A computational procedure to determine flash temperatures in the piston‐ring and cylinder‐sleeve tribosystem is presented. The theoretical results, including film thickness, sliding speed, gas pressure, and flash temperatures for a complete crankshaft cycle are also presented.
Influence of viscosity index improver, molecular weight, and base oil on thickening, shear stability, and evaporation losses of multigrade oils
Authors: Bartz Wilfried J.
Published: July 2006

Some SAE 15W‐40 multigrade oils were formulated, using polymethacrylate (PMA) viscosity index improvers of different molecular weights, with a mixture of N 150 and N 500 as the base oil. Kinematic and dynamic viscosities, borderline pumping temperatures, pour points, shear stability, and evaporation losses were measured. The results confirm that viscometric properties as well as shear stability depend strongly on the polymer concentration and molecular weight of the VI improvers. However, evaporation losses are dominated by the volatility properties of the base oil.
The hydrocarbon/water interfacial behaviour of alkyl aryl sulphonates
Authors: Singh A. K.
Published: July 2006

The interfacial tension and solubilisation characteristics of the alkane/water interfaces of a series of alkyl aryl sulphonates synthesised with 1‐butanol as a co‐surfactant have been studied. It was observed that there is a narrow range of carbon numbers of these sulphonates at which maximum solubilisation of a particular alkane occurred. This range shifted progressively to a higher value, with a corresponding increase in the carbon number of the n‐alkane. The extent of solubilisation of the alkane is highly dependent on the structure of the hydrocarbon portion of the sulphonate. Unexpectedly, an ultra‐low interfacial tension seems not to be an important prerequisite for the solubilisation of hydrocarbon in the aqueous surfactant phase. The free energy decrease required for solubilisation seems to be far more dependent on the energetic interactions connected with entropy parameters. The conformational aspects of the hydrocarbon portion of sulphonate molecules, as a consequence, seem to play a decisive role in molecular interactions, leading to solubilisation of a large quantity of a particular hydrocarbon in aqueous solution of a given sulphonate. The present work aims at understanding the selection criteria for sulphonates in applications involving solubilisation and ultra‐low interfacial tension at the hydrocarbon/water interface, such as those in insecticidal/pharmaceutical formulations, fire‐resistant hydraulic fluids and enhanced oil recovery.
Performance evaluation of some organic compounds of zinc as additives for lubricating oils
Authors: Stãnescu Chiriaca , Boiangiu Victor , Dinoiu Vasile , Florescu Danilian
Published: July 2006

Several organic compounds of zinc were synthesised, blended in oil, and evaluated in laboratory bench tests for AW/EP, friction, and deposition properties. Two of these, a zinc dithiophosphocarbamate and a package based on zinc dialkyldithiophosphate plus a sulphurised compound, appear to give the best overall performance.
An analytical study of the fluid film force in finite‐length journal bearings. Part I
Authors: D'Agostino V. , Guida D. , Ruggiero A. , Senatore A.
Published: July 2006

A theoretical study has been carried out to determine an approximate analytical description of the fluid film force of a symmetrical rigid rotor supported on two finite‐length lubricated journal bearings. The analysis has been conducted assuming the Warner solution for the pressure field. The analytical approach to studying the behaviour of a system is more effective than numerical investigation, and makes it possible to cover not only an individual system, but also the whole class to which that system belongs. Furthermore, the model proposed allows quick analytical determination of the stiffness and damping coefficients.
Friction measurements of a square box deep‐drawing process
Authors: Wang Ye , He Dannong , Zhang Yongqing
Published: July 2006

The role of the lubricant during square box forming has been studied with a drawing lubricant performance assessment simulation system. Probes and sensors set up in different parts of the die are used to obtain the friction coefficient directly during drawing. The main finding is the validation of the relationship of the friction coefficients at the box corner, at the box side, and at the box side furthest away from the punch position. Also, a mathematical model has been set up. This model can be used to study the use of lubricant during large‐scale blank forming or to provide a new way to determine the friction boundary conditions in computer simulations.
Piston deposit control using metal‐free additives
Authors: Hamblin P. C. , Rohrbach P.
Published: July 2006

Engines can be damaged in many ways: the principal oil‐related problems are due to deposit formation and viscosity increase. A first step in minimising the consequences of oil degradation is to reduce the formation of sludge and deposits. This can be accomplished by the judicious use of metal‐free (ashless) anti‐oxidants. Detergent/dispersant additives play a critical role in extending lubricant life by cleaning up deposits and keeping them in solution, and by neutralising acids formed during the combustion process. Several different types of antioxidants that can successfully eliminate precursors that lead to deposit formation and viscosity increase in oils in both gasoline and diesel engines have been identified. A novel, ashless, multifunctional additive that confers thermo‐oxidative stability and friction modification to engine lubricants is described here.
Friction‐reducing and antioxidant capabilities of engine oil additive systems under oxidative conditions. II. Understanding ligand exchange in a molybdenum dialkyldithiocarbamate/zinc dialkyldithiophosphate additive system in various base oils
Authors: Jensen R. K. , Korcek S. , Johnson M. D.
Published: July 2006

The ligand‐exchange reactions between molybdenum dialkyldithiocarbamate, Mo(dtc)2, and zinc dialkyldithiophosphate, Zn(dtp)2, have been investigated during inhibited oxidation in a model hydrocarbon (hexadecane) and in a series of Group I–IV base oils at 160°C. These investigations revealed that the ligand exchange leads to formation of single‐exchange products, Mo(dtc)(dtp) and Zn(dtp)(dtc), and double‐exchange products, Mo(dtp)2 and Zn(dtc)2, and that the extent of the exchange is significantly affected by oxidation and inhibition reactions involving the original additives, the ligand‐exchange products, the base oil, and base oil‐derived oxidation products.

It is concluded that there are two reaction sequences that control the product distribution and additive consumption during oxidation in different base oils. The first sequence involves the formation of peroxy radicals and hydroperoxides, and the decomposition of hydroperoxides by Zn(dtp)2 and Zn(dtp)(dtc). One of the most important factors affecting this sequence is the base oil oxidisability. The second sequence involves inhibition of oxidation by peroxy radical‐trapping antioxidants naturally present in or added to the oil, or formed during the oxidation. Zn(dtc)2 and Zn(dtp)(dtc) appear to be very effective in this respect and are, therefore, preferentially consumed. This preferential consumption shifts the ligand‐exchange equilibrium towards the formation of Mo(dtc)(dtp) and Mo(dtp)2.

The combined effect of the two sequences depends on base oil properties. The first sequence predominates in base oils exhibiting high oxidisability (e.g., in Group I oils) and the second in paraffinic oils, such as Group III and IV oils, having low oxidisability and no sulphur or aromatics. the retention of friction‐reducing capability with the Mo(dtc)2/Zn(dtp)2 additive system during oxidation appears to be tied to the first sequence, which leads to consumption of Zn (dtp)2, since the friction‐reducing capability ceases when Zn (dtp)2 is consumed and hydroperoxides can accumulate in the system. Consequently, the best retention of friction‐reducing capability is achieved in bases oils with low oxidisability.
A tribological study of (2‐sulphurone‐benzothiazole)‐3‐methyl‐dibutyl borate
Authors: Weijiu Huang , Junxiu Dong , Fenfang Li , Guoxu Chen , Boshui Chen
Published: July 2006

An organic compound containing S, N, B, and O was synthesised by reacting 2‐mercaptobenzothiazole and formalin in ethanol solution, the resulting product then being reacted with butanol and boric acid in toluene solution. The tribological performance of the novel compound when added to liquid paraffin was evaluated using a four‐ball tester and a ring‐on‐block machine. The relationship between performance and concentration was analysed, and the results show that the compound possesses good antiwear and load‐carrying abilities. The mechanism of action of the additive was investigated using X‐ray photo‐electron spectroscopy (XPS). Surface analysis indicated the formation of a protective film containing FeSO4, an organo‐sulphur compound, FeS2, borate, and an organonitrogen compound. This protective film formed during sliding processes contributes to the increase in wear resistance.
Geometric effects in high‐temperature vapour‐phase lubrication using hydrocarbon feed gases
Authors: Gardner J. E. , Sawyer W. G. , Blanchet T. A.
Published: July 2006

The effectiveness of ‘far‐field’ vapour‐phase lubrication, in which areas of a bearing surface that are cycled through the contact are exposed to vapour while outside the contact, has been demonstrated in both sliding and combined roll slide tests using acetylene vapours to deposit pyrolytic graphite. Friction coefficients as low as μ = 0.008 have been measured for steel at 540°C with far‐field acetylene concentrations as low as 5%. Effective vapour‐phase lubrication depends on solid lubricant deposition that exceeds the contact's capacity to remove solid lubricant through wear. While the rate of removal is increased by increasing the sliding velocity, in far‐field vapour‐phase lubrication the rate of lubricant deposition, and therefore the lubrication effectiveness, is augmented by increased areas available for far‐field deposition, such as those provided by performing wear tests with increased wear‐track diameters. These geometric concepts may be considered in rolling‐element bearing and gear set applications where vapour‐phase lubrication is to be employed.
Film‐forming additives ‐ direct and indirect ways to reduce friction
Authors: Spikes H. A.
Published: July 2006

This paper reviews the current understanding of lubricated contacts and the origins of friction in terms of the Stribeck curve. It discusses the various ways that lubricant additives can modify friction in thin‐film lubricated contacts, examining both the nature and properties of the films formed by these additives, as revealed by film thickness measurements, and their consequent effect on the Stribeck friction curve.
Lubrication potential of boron compounds: An overview
Authors: Choudhary R. B. , Pande P. P.
Published: July 2006

Boron compounds are emerging as promising materials for a wide range of applications in automotive and industrial lubrication systems. Several studies conducted on boron compounds have revealed that they exhibit desirable properties for preparing stable and compatible lubricant components for a new generation of lubricating oil formulations. Boron‐containing lubricants have major tribological advantages, such as antiwear efficiency, good film strength, high‐temperature resistance, and self‐lubricating properties. The increasing number of patents concerning boron‐containing lubricants illustrates commercial interest in this area. Boron lubricants can be used in many forms, such as oxides, esters, and boric acid. Therefore, it can be expected that a new generation of lubricant formulations includes boron compounds. This paper presents an overview of various solid and liquid lubricants containing boron as an important ingredient, and is intended to aid the development of new lubricants.
Effect of the structure and metal atom of dialkyldithiophosphate derivatives on the wear behaviour in steel‐zirconia contacts
Authors: Margielewski L. , Stanecka R.
Published: July 2006

Wear investigations concerning the different structures and metal atoms of metal dialkyldithiophosphates (MeDTPs) were conducted using a ball‐on‐disc apparatus. Steel ball bearings (3.175 mm in diameter) and counterface discs, made of hot pressed ZrO2 partially stabilised by Y2O3, were used. The synthesised MeDTPs were made up of primary linear aliphatic alcohols with hydrocarbon lengths varying from 8 to 16 carbon atoms, and contained the following metals: zinc(II), iron(III), gallium(III), antimony(III), and copper(II). Tests were performed at room temperature. The sliding speed was set to a constant 0.03 m/s, and a constant 30 N load was used. The additives investigated were used as solutions in n‐hexadecane.

The study also focused on the influence of additive concentration on wear. It was found that the effectiveness in reducing wear depends both on the metal atom and on the length of the hydrocarbon chain in the additive's molecules. The lowest wear volumes were observed for additives with n‐octyl and n‐tetradecyl hydrocarbon chains. The worst antiwear performance was observed for n‐dodecyl derivatives. For almost all additives, more concentrated solutions resulted in less wear. Some friction coefficient results are also presented.
Borate esters used as lubricant additives
Authors: Yao J. B. , Wang Q. L. , Chen S. Q. , Sun J. Z. , Dong J. X.
Published: July 2006

Borate esters possess friction‐reducing, antiwear, and anti‐oxidant characteristics when blended in lubricating oils. However, borate esters are susceptible to hydrolysis. The formation of a stable five‐member ring structure in the ester molecules, involving coordination of nitrogen with boron, contributes substantially to the resistance to hydrolysis of borate esters. The susceptibility of borates to hydrolysis can be reduced by introducing N,N‐dialkylaminoethyl groups with alkyl radicals containing more than three carbon atoms. X‐ray photo‐electron spectroscopy and X‐ray diffraction reveal that the borate ester can be adsorbed on the rubbing surface, and some of the adsorbed borate film degrades and forms boron nitride. Four‐ball wear tests indicate that the combination of oil‐soluble copper, tin, and cadmium compounds with organoborates gives better antiwear properties than the components separately. An antiwear synergistic mechanism is postulated in which borates with electron‐deficient boron p orbitals catalyse the tribo‐reduction of the metal compounds on the rubbing surfaces, producing elemental metals.
Basics: Current base oil quality and technological options for its improvement— an Overview
Authors: Anwar M. , Kaushik R. S. , Srivastava Manoj , Kumar Manoj , Garg M. O.
Published: July 2006

Recent technological developments have revolutionised the lubricant industry by spurring a widespread quality improvement in both base oils and additives, giving superior finished lubricants. The upgrading of base oils is being brought about by more demanding requirements from original equipment manufacturers (OEMs), by government regulations, and through consumer awareness, environmental concerns, decreasing supply of high‐quality lubricant‐bearing crudes, and expanding markets worldwide.

Present‐day lubricant demand is for maximum oxidation stability, superior low‐temperature performance, low volatility, and improved additive response, which are difficult to achieve through conventional processing. Conventional solvent lubricant refining produces base oils with a viscosity index (VI) of 100 with a fair amount of sulphur and aromatics, i.e., Group I base oils only. The current requirements of high‐performance base oils can conveniently be met through the hydroprocessing route. Depending upon the severity level, hydroprocessing is able to produce base oils of VI 95–110, in addition to low sulphur and high saturates content (Group II and Group III) by transforming the undesirable molecules into more useful structures. In countries such as India, a hybrid approach offers a technical solution to meet current demands for lubricant quality. This approach can be implemented in existing lubricant refineries without entailing major changes in refinery configuration, besides being cost‐effective.

This paper describes the current requirements of modern lubricants in relation to API Groups and trends in these, and describes a sequence of technologies involving solvent refining, a cost‐effective hybrid scheme, and more recent hydroprocessing that allows a cost‐effective upgrading of Group I refining process. A case study is given that discusses the adoption of the hybrid scheme in Indian refineries.
Application of quantitative 13C nuclear magnetic resonance spectroscopy to the characterisation of solvent‐refined aromatic‐rich lubricant base oils
Authors: Adhvaryu A. , Erhan S. Z. , Singh I. D.
Published: July 2006

Nuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful technique for studying the molecular composition of base oil matrices. The usefulness of this technique lies in its ability to explain the chemistry involved in the molecular changes observed in various lubricant refining and extraction stages. This paper discusses the use of this technique in understanding the variation of gross properties observed in base oils during lubricant processing steps. The variations in weight percent of sulphur, viscosity index (VI), Conradson carbon residue (CCR), characterisation factor (KUOP), etc., are explained at the molecular level using high‐resolution quantitative 1H and 13C NMR. A single well‐recorded quantitative spectrum of a sample can be used to generate sufficient information on the different properties used for the specification of base oils.
Friction‐induced two‐dimensional solid films from lubricant additives
Authors: Martin Jean‐Michel , Grossiord Carol , Varlot Karine , Vacher Béatrice , Le Mogne Thierry , Yamada Yasuhisa
Published: July 2006

Tribochemical interactions between some lubricant additives, namely zinc dithiophosphate (ZnDTP), an antiwear additive, molybdenum dithiocarbamate (MoDTC), a friction modifier, and overbased calcium borate (OCaB) detergent, have been investigated. The nature of the tribofilms formed was studied by combining high‐resolution transmission electron microscopy of wear fragments and inside wear scars with micro‐spot X‐ray photoelectron spectroscopy at the same location of the wear track (‘dual’ analysis).

The OCaB/ZnDTP/MoDTC ternary system provides both a low wear rate and ultralow friction, while adding detergent and anti‐corrosion properties to the formulation. The analytical data indicate that such a synergistic effect can be attributed to an outstanding feature of the tribofilm nanostructure: it is composed of perfectly oriented MoS2 single sheets embedded in a single‐phase calcium and zinc borophosphate glass. Compared to phosphate alone, MoS2 sheets are oriented by the borophosphate phase. This could be related to a template effect of friction‐aligned planar molecules of the glassy borate polymer.
Influence of the structure of polysulphide additives on the shiftability of manual transmissions
Authors: Shirahama Shinichi , Ohkawa Tetsuo
Published: July 2006

The shiftability of manual transmissions is known to be strongly affected by the nature of the transmission oil. When conventional sulphur—phosphorus (SP) additives are used in the oil, gear clashing, sticking, and other problems occur. As reported previously, these problems are caused mainly by the polysulphide used in the SP additives. This paper reports on a study of the effect of the structure of the polysulphide's hydrocarbon chain on the synchromesh characteristics. It is found that polysulphides with long hydrocarbon chains have high kinematic friction coefficients and low static friction coefficients. It is also shown that this phenomenon occurs because of the adsorption of the polysulphide on to the copper alloy of which the gear synchroniser ring is made. By using a polysulphide with a long hydrocarbon chain it is possible to develop transmission oils that have superior load‐carrying capacity and better shiftability even when compared with the latest transmission oils that contain metallic detergents.
Lubrication at 750°C in a vacuum by a transfer film from self‐lubricating composites for roll/slide contact of Si3N4
Authors: Suzuki M.
Published: July 2006

Roll/slide friction tests were carried out at a temperature of 750°C in a vacuum. Disc specimens were made of Si3N4 with or without a sputtered MoS2 film. A pin specimen was rubbed against one disc to supply a lubricating transfer film. With a pin made of an MoS2‐based composite, the friction coefficient was around 0.3 and almost no wear of the discs was observed after 24 h of operation at a load of 50 N, a rotating speed of 0.5 m/s, and a slip ratio of 10%. Transferred patchy MoS2 films were observed on the friction track. With a pin made of Ni‐based composite containing BN and graphite, the friction coefficient increased from 0.2 to 0.7 over a test time of about 8 h and severe disc wear was found. In an additional test using Si3N4 discs with a sputtered MoS2 film without a pin, the friction coefficient was about 0.3, and no wear of the discs was found after 24 h of operation. The appearance of the friction track was similar to that in the test using the MoS2‐based composite pin. It seems that the sputtered MoS2 film wore, but wear particles reattached on the friction path to develop an effective lubricating film. These results demonstrate the effectiveness of transfer film lubrication for long‐term operation in a high‐temperature vacuum, and the superior ability of MoS2 to develop an effective transfer film.