bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidative stabilisation of synthetic fluids and vegetable oils
Authors: Hamblin Peter
Published: July 2006

The use of ashless antioxidants to increase the useful working life of synthetic fluids, such as polyalphaolefins, polyalkylene glycols and carboxylic acids, is discussed, and some general guidelines are proposed. The application of ashless antioxidants in controlling the oxidative degradation of several different types of biodegradable vegetable oil is illustrated. The action of the naturally occurring antioxidant, vitamin E, in some of these fluids has been examined and some preliminary results are reported.
Wear performance of tribologically modified thermoplastic composites at elevated temperatures
Authors: Reinicke R. , Hoffmann J. , Friedrich K.
Published: July 2006

The use of injection moulded thermoplastic composites is increasing, but without fillers, reinforcements, or lubricants, they are limited by their thermal behaviour. This study looks at four polymers — polyamide 46, polyphthalamide, polyetherimide, and polyphenylenesulphide — containing first glass fibres as reinforcement, and a second version with added PTFE. Two types of wear test were undertaken, sliding wear (pin‐on‐disc and block‐on‐ring), and reciprocally fretting wear. The test materials showed different wear rates both under different tests and at various temperatures.
Hydrolytic stability of synthetic ester lubricants
Authors: Boyde S.
Published: July 2006

This paper looks in detail at hydrolysis of esters. While this is not normally a problem, hydrolytic stability can be an important consideration, e.g., in air compressors. The paper looks first at the synthesis of esters, which is a reversible reaction of acid + alcohol ↔ ester + water, usually involving a catalyst. Two mechanisms of ester hydrolysis, namely base‐catalysed and acid‐catalysed, are described as being most relevant to lubricant esters, the former being less likely than the latter. Two extended tests are described which have been used in the author's laboratory, a beverage‐bottle test (modified ASTM D‐2619), and a sealed‐tube test, for hydrolytic measurement. The paper goes on to look in detail at the effect of ester structure on rate of hydrolysis, in terms of resonance effects and steric effects, on the effect of impurities, and of acidic and acid catcher additives.
A friction coefficient of 0.05 in aqueous systems
Authors: Zwinselman Jan
Published: July 2006

Low friction coefficients, i.e., below 0.10, in mineral oil based lubricants have been traditionally obtained using glycerol mono oleate, molybdenum dithiocarbamate or molybdenum dithiophosphate. In aqueous systems this is more difficult to achieve, and wear protection is also problematic due to the polar nature of the substrate. There is substantial interest in low toxicity/ecotoxicity additives, especially in metalworking fluid applications, where disposal of the finished fluid can be expensive. In this paper, a novel ashless (metal‐free) friction modifier with antiwear properties, specifically designed for aqueous systems, is reviewed. This additive does not contain phosphorus, sulphur, or halogens. Some preliminary results in water based lubricants, for example, polyalkylene glycols, for metal forming applications are presented.
Environmentally adapted lubricants, Part II. Hydraulic fluids
Authors: Pal Mahendra , Singhal Sudhir
Published: July 2006

Current technologies relating to hydraulic fluids are mostly either mineral based, synthetic based, or water‐based. Mineral oil based hydraulic fluids tend to be used for their excellent lubrication characteristics, economic viability, and so account for almost 90% of hydraulic fluids, while waterbased fluids tend to be employed in fire hazard applications. Synthetic hydraulic fluids possess superior properties to mineral oils, but their higher price limits their application to aerospace and special applications under severe conditions. In recent years, biodegradable hydraulic fluids, which are readily decomposed by micro‐organisms, have come into focus due to the rise in environmental consciousness in European countries, particularly Sweden and Germany, and with this, vegetable‐based fluids.

In the present paper, the main categories of hydraulic fluids, including environmentally friendly fluids, are discussed in an overview of the state of technology in this area. Current governmental regulation, and the properties required of environmentally adapted fluids, and an appraisal of the current practices in various countries are also given.

In an earlier paper*, the authors reviewed the key aspects of and requirements for environmentally adapted lubricants, namely, chemical composition, eco‐toxicity, biodegradability, bio‐accumulation, eco‐labelling schemes, and life‐cycle analysis.

In the present paper, the main categories of hydraulic fluids, including environmentally friendly fluids, have been described. In Part I*, the authors reviewed the key aspects of and requirements for environmentally adapted lubricants.
Dynamic friction measurements with an atomic force microscope on polymer surfaces
Authors: Krotil Hans‐Ulrich , Marti Othmar
Published: July 2006

The combination of scanning friction force microscopy (SFFM) and lock‐in techniques leads to dynamic SFFM (DSFFM) and provides great advantages in friction force studies with sub‐micrometre resolution. In this paper are presented measurements on thin adsorbed organic films on polymers (polymer blend of 75% poly(allylaminehydrochloride) (PAA) and 25% poly(diallyl‐dimethylammonium chloride) (PDDAC)) and on mica (as a reference). The amplitude and phase response as a function of the excitation amplitude can be explained on hard surfaces by a simple static and dynamic friction model. This model allows us further to distinguish static friction forces and kinetic friction forces in a quantitative way. Furthermore, we demonstrate the use of these spectra to determine the correct modulation amplitude of the excitation to achieve the optimal friction contrasts directly. Polymer data suggest that the viscoelastic shear flow under the atomic force microscope (AFM) tip is responsible for the shape of the phase and amplitude spectrum. Lastly, we demonstrate that DSFFM is a useful technique for surface characterisation in situations where SFFM may not be adequate.
Nanoscale boundary lubrication of diamond‐like carbon coatings with fluorinated compounds
Authors: Kajdas C.
Published: July 2006

Progress in the technology of magnetic media has brought about a remarkable increase in recording density. The most important factor determining the utility of magnetic disks is durability against head wear, and this durability is controlled by several factors. The present paper discusses the tribology of these media, particularly from the viewpoint of boundary lubrication. In that context there are two characteristic features of this lubrication regime: specific standard lubricants (fluoropolyethers such as Z‐DOL and perfluo‐ropolyethers such as Z‐15) and the newer application of these lubricants in the form of films only a few nanometers thick Advanced phosphazene‐type fluorinated compounds are of most interest at present, so these compounds are discussed in more detail. The emphasis is on X‐1P lubricant used either alone or as an additive for fluoro‐ and perfluoropolyethers deposited on protective diamond‐like carbon coatings.
Application of waste carboxylic acids to the manufacture of biodegradable polyolester base oils
Authors: Beran E.
Published: July 2006

The results described in this paper represent a contribution towards finding feedstocks, such as monocarboxylic acids, for the production of polyolester base oils. The research has shown that it is possible to obtain a mixture of monocarboxylic (butyric, valeric, and caproic) acids from the waste stream produced by the catalytic oxidation of cyclohexane to cyclohexanone in the industrial production of caprolactam. The mixture of C4—C6 carboxylic acids separated from this waste by distillation was used to esterify neopentyl alcohols such as trimethylolpropane (TMP) and pentaerythritol (PE). Thus, polyolester synthesis was strongly dependent on the choice of suitable catalyst and the neturalisation of unreacted acids. Polyolester oils obtained from TMP or PE with monocarboxylic C4—C6 acids have better physicochemical properties than conventional mineral oils, namely ISO 10 or ISO 22, including higher viscosity indices, higher flash points, lower pour points, and lower volatilities. In addition, the polyolesters tested are readily biodegradable under the conditions of the CEC‐L‐33‐T‐82 test and the Zahn‐Wellens test.
Low‐temperature characteristics of synthetic fluids
Authors: Boyde S.
Published: July 2006

The low‐temperature fluid properties of synthetic base fluids are described, showing how these properties are related to the molecular structure of the base fluid. Examples are given of how the principles of molecular design can be used to improve the low‐temperature properties of synthetic base fluids, focusing on esters derived from both natural and petrochemical raw materials. Results of studies using calorimetric and spectroscopic methods, including differential scanning calorimetry and nuclear magnetic resonance are presented, showing how these techniques can be used to give more detailed insight into the changes occurring in fluids at low temperatures.
Synthetic aluminium complex grease: A tribological evaluation using a four‐ball test
Authors: Singh Tarunendr , Bhan A. K.
Published: July 2006

This paper describes the preparation and performance evaluation of a synthetic aluminium complex grease. The aluminium complex grease was prepared in situ by reacting stearic acid and benzoic acid in the presence of a synthetic base oil, polyalphaolefin. The preparation of the soap (aluminium benzoate stearate hydroxide) was monitored using Fourier transform infrared. Two different extreme‐pressure additives blended with the prepared aluminium complex grease were evaluated for their extreme‐pressure activity in four‐ball and Timken tests. These greases exhibited higher Timken OK loads (60 lb), lower values of wear‐scar diameter at higher loads, and higher values of weld load in the four‐ball test than the aluminium complex grease without additive. The blended greases were also found to pass rust and corrosion, oxidation‐stability, and shear‐stability tests. The topography of the specimens after four‐ball testing was studied with scanning electron microscopy.
Base fluid parameters for elastohydrodynamic lubrication and friction calculations and their influence on lubrication capability
Authors: Larsson Roland , Kassfeldt Elisabet , Byheden Åke , Norrby Thomas
Published: July 2006

In this study, base fluid parameters for elastohydrodynamic lubrication (EHL) and friction analyses have been determined experimentally. The viscosity at atmospheric pressure, η0, the pressure‐viscosity index, α, and the EHL friction coefficient, γ, are important parameters in EHL theory and they are crucial in the selection of efficient lubricants for different applications. This investigation focuses on three important lubrication mechanisms: the capability of forming a separating lubricant film, the friction generated in a lubricated contact, and the height of pressure peaks, such as the outlet pressure spike and pressure ripple caused by surface roughness. The influence of different lubricant parameters on these three mechanisms is discussed. The value of α is measured in a Couette high‐pressure viscometer, and the value of γ is obtained from a jumping‐ball device. Other parameters discussed are temperature‐viscosity coefficient, β, bulk modulus, B0, thermal conductivity at atmospheric pressure, λ0, and heat capacity unit volume, ρcp0.

A comparison between traditional mineral base oils and environmentally adapted oil based on rapeseed oil and synthetic esters contributes to the further understanding of the performance of these new materials in lubrication applications. It is shown that rapeseed oil and synthetic esters have good lubricating properties and are, in most cases, better than mineral oils.
Lubricity characteristics of ethyl hexyl esters of mono‐, Di‐, and triethenoic acids
Authors: Sharma Anju , Chhibber V. K. , Pal Mahendra , Anand O. N.
Published: July 2006

Ethyl hexyl esters of oleic, linoleic, and linolenic acids were synthesised and thermally polymerised to obtain products with viscosities in the range of hydrocarbon lubricants at 100°C (11–22 cSt). Molecular weight, elemental analysis, IR, 13C NMR, and intrinsic viscosity data showed that most of these derivatives are mixtures of monomers, dimers, and trimers and have linear and cyclic products with predominantly trans characteristics.

The lubricity characteristics were determined on a friction and wear tester under conditions of thick‐film lubrication. A comparison was made with hydrocracked hydrocarbon lubricants of comparable viscosities at 100°C and comparable viscosity indices.

It is inferred that all the esters maintained relatively thicker surface films and much lower friction coefficients than the hydrocarbon oils. The wear‐scar data show that the antiwear characteristics of polymerised ethyl hexyl oleate and linoleate are only slightly inferior to those of the hydrocarbon oils, but at higher temperatures their antiwear characteristics rapidly deteriorate while the friction coefficients markedly increase and become comparable to those of hydrocarbon oils. These studies are being undertaken with a view to selecting and modifying vegetable oils containing mixtures of fatty acids for obtaining esters of outstanding friction, wear, and film‐forming characteristics.
A comparative life cycle assessment of the manufacture of base fluids for lubricants
Authors: Våg C. , Marby A. , Kopp M. , Furberg L. , Norrby T.
Published: July 2006

A comparative life cycle assessment (LCA) study of three types of base oils used in the manufacture of hydraulic fluids has been carried out, and is reported here. The fluid types investigated are a mineral oil, a synthetic ester, and a rape seed triglyceride oil. The applications chosen for the finished lubricants are in mobile hydraulic systems in forestry operations, some of which are almost 100% total loss applications. The scope and limitations of the LCA model are discussed, and conclusions drawn concerning the application of LCA models as evaluation tools for the development of environmentally adapted lubricants. The methodology used is compatible with the ISO 14000‐type industrial standard.
Eco‐friendly base fluids for lubricant oil formulations
Authors: Bisht R. P. S. , Kaul Savita , Nagendramma P. , Bhatia V. K. , Gupta A. K.
Published: July 2006

There is an increasing move towards the use of environmentally safe lubricants. However, the development of a common biodegradable base stock that could replace conventional ones is a big challenge. Synthetic lubricants, whether synthetic hydrocarbons, organic esters, or others, all have problems associated with their use. However, in general terms synthetic lubricants protect better, last longer, and outperform their conventional mineral‐based counterparts in certain applications. Future lubricant specifications in view of the demand for improved performance to meet stringent environmental regulations are the main drivers for new technological developments. As part of a study to produce polyol ester lubricant base stocks from C5 polyols and C6‐C14 carboxylic acids in the presence of eco‐friendly catalysts, a series of products has been synthesised. A biodegradable lubricant formulation for automotive transmission fluids has been developed based on a synthesised product as a base fluid. This paper reports on the physico‐chemical characteristics and performance evaluation results of this formulation, which is a promising base stock for automotive transmission fluids.
Structurally modified polyglycols as biodegradable base stocks for synthetic lubricants
Authors: Beran E.
Published: July 2006

Lubricants of novel formulation should have low toxicity and be readily degraded in the environment. Polyglycols (PAGs), which are homopolymers of ethylene, propylene, or (rarely) butylene oxides, or are copolymers of ethylene and propylene oxides, constitute a group of chemical raw materials with a wide range of industrial applications. They are also used in the synthetic lubricant industry. The properties and applicability of certain PAGs depend on a variety of factors, such as the conditions of preparation, the type of starter and alkylene oxide used, and parameters controlling the structure and molecular weight of the final product. However, of the wide range of available PAGs, not many display properties that might be useful in the production of lubricants, and not many fulfil the biodegradability criteria required in standard test procedures (e.g., OECD) for environmentally friendly base oils. Studies carried out to obtain a novel assortment of base oils have shown that the modification of commercial PAGs by esterification of their hydroxyl groups (both in polyoxyalkylenediols and polyoxyalkylenetriols) yields products with the desired properties. For example, esterification of polyoxyethylenediol of a molecular weight of 400 modified its viscosity, pour point, and water solubility, but did not affect its biodegradability (over 80% in Zahn‐Wellen's test: ISO 9888; OECD 302B).
Sliding wear behaviour of PEEK‐PTFE blends
Authors: Hufenbach W. , Kunze K. , Bijwe J.
Published: July 2006

The role of PTFE in tailoring the tribological performance of PEEK is not clear from the literature, and conflicting evidence is reported about its ability to improve friction, wear, or both. Moreover, little has been reported on the optimum composition of such blends for the best possible combination of mechanical and tribological properties. Hence, in this work various blends of PEEK with PTFE have been injection moulded and characterised for their mechanical properties. Their friction and wear behaviour was evaluated using a pin‐on‐disc machine. It was observed that the inclusion of PTFE powder not only removed scuffing problems associated with the friction behaviour of PEEK, but also improved both friction and wear characteristics. A blend with 7.5 wt. % PTFE showed the best wear behaviour, while a blend with 30 wt.% PTFE exhibited the best friction performance. A concentration of 7.5 wt. % PTFE was thought to be the optimum amount for the best possible combination of mechanical and tribological properties.
Wear reduction using some extreme pressure lubricant additives and their tribological studies
Authors: Mammen A. , Agarwal C. V. , Verma V. K.
Published: July 2006

Certain S‐containing organic compounds were synthesized and their extreme pressure (EP) properties assessed. The series of compounds studied were: S‐alkylisodithiobiurets, alkyl‐S‐alkyl xanthates, S‐alkylisothioamides, S‐benzylisothiocarbamides and 1‐formamidino‐2‐benzyliso‐3‐arylthiocarbamides. These additives were compared with a commercial additive. The tribological end effects were studied using a Scanning Electron Microscope. Some of the compounds tested were found to be effective EP additives.

Wherever possible, a plausible explanation for the enhanced activity has been given, and we have attempted to correlate the effect of substituents on efficiency. Also, the effect of additives on balls of different compositions is discussed. The possibility of replacing the costly chromium steel alloy balls by less costly mild steel balls is suggested.

Some of the additives developed are found to be effective on balls of certain compositions while they are a total failure on the chromium steel balls. The studies reveal that some additives are effective on mild steel balls as well as chromium alloy steel balls. They can be very good substitutes for commercial additives with bearing balls of standard composition.

As chromium alloy steel balls are much costlier there is a need to replace expensive alloy steel balls with cheaper low carbon steel balls, for certain specific purposes. This can be achieved by using suitable indigenous additives that are found to be effective on low carbon steel balls.
Micellar structure of alkaline earth metal alkylarylsulphonate detergents
Authors: Tricaud C. , Hipeaux J. C. , Lemerle J.
Published: July 2006

Overbased and neutral magnesium and calcium salts of sulphonic acids were prepared, these salts having a very complex micellar structure when added to a lubricant oil. Using solutions in isooctane, the authors studied this structure by ultracentrifugation. The following results were obtained: a correlation between the alkaline reserve of additives and the size of the micelle; a difference in the size of the micelle in relation to the earth metal used; and the influence of the solvent used in the evolution of the micellar structure in the solution.
The effects of engine oil additives on valve train wear
Authors: Shirahama S. , Hirata M.
Published: July 2006

Preventing valve train wear in automotive engines is one of the most important properties of an engine oil. However, the influence of engine oil additives on valve train wear has not been sufficiently clarified.

In this investigation, the antiwear performance of additives (such as ashless dispersants, metallic detergents and zinc dithiophosphate ‐ ZDTP) and the influence of the interaction of the additives were evaluated.

Secondly, metallic detergents were considered. An overbased calcium sulphonate and an overbased phenate were found to have good anti‐scuffing performance when evaluated in engine tests and in Falex wear tests. However, from the results of four‐ball tests, these additives did not appear to have many extreme pressure properties. From surface analyses, it was determined that a calcium carbonate film was formed on the sliding surface of the Falex test piece, and this film provided good protection against wear.

Finally, the interaction of ZDTP, succinimides and calcium detergents and their influence on valve train wear were studied. The decomosition temperature of ZDTP increased with certain additives. including the succinimide. As a result, scuffing was more prone, at temperatures below those increased temperatures. Also, changes in additive concentration on the sliding surface, due to competitive adsorption, altered the antiwear performance of the oil.
Effect of sulphur‐type extreme‐pressure additives on wear in rolling‐sliding contact
Authors: Masuko M. , Akatsuka K. , Okabe H.
Published: July 2006

This paper looks at the wear of steel under lubricated rolling‐sliding contact, with two paraffinic oils and a pure n‐hexadecane. A two‐disc apparatus was used, with a constant applied load, the surfaces being analyzed by X‐ray photoelectron spectroscopy. The oils were tested with and without additives (dibenzyl disulphide and diphenyl disulphide), and the differences analyzed.
The influence of chemical structure of certain nitrogen‐containing organic compounds on their antiwear effectiveness: The critical role of hydroxy group
Authors: Wei D. , Han X. , Wang R.
Published: July 2006

Certain nitrogen compounds and their derivatives used as antiwear additives in base stocks have been tested on a four‐ball machine and an HQ‐1 tester for their relative antiwear effectiveness. The preliminary results indicate that the heterocyclic nitrogen compounds, in general, have a beneficial effect on the antiwear performance of base stocks. Hydroxy groups involved in some nitrogen‐containing compounds have been found to improve their antiwear performance significantly. In particular, one of the hydroxy‐substituted benzothiazoles is most effective in wear reduction and anti‐scuffing. However, the beneficial effect of a hydroxy group has not been observed for short‐chain amines.
Critical conditions for wear in pivoted follower valve train systems
Authors: Bell John C.
Published: July 2006

There are numerous wear problems associated with the use of pivoted cam follower valve train systems in modern high‐speed automotive engines. These problems have led to the introduction of an increasing number of engines of this type as specification tests to assess the antiwear performance of lubricants. Critical conditions for wear in these systems have been identified by the application of a steady‐wear process model to the kinematic analysis of the cam/follower contact cycle. The positions of maximum wear identified by this technique showed better agreement with worn engine components than the more commonly used criteria of maximum contact pressure and oil film thickness.
Ashless antioxidants, copper deactivators and corrosion inhibitors: Their use in lubricating oils
Authors: Hamblin P. C. , Kristen U. , Chasan D.
Published: July 2006

This paper reviews the use of copper deactivators and iron corrosion inhibitors in lubricating oils. The auto‐oxidation process is described in terms of initiation and chain propagation, branching and termination, and the primary and secondary oxidation inhibitors are described. Copper deactivators and corrosion inhibitors nature and action are discussed, and the paper also examines the applications for these additives.
Measurement of lubricating film thickness, temperature and pressure in gear contacts with surface topography as a parameter
Authors: Peeken H. , Ayanoglu P. , Knoll G. , Welsch G.
Published: July 2006

Thin film transducers, sputtered onto a tooth flank, are used to measure temperature, pressure and oil film thickness profiles in gear contact. The former two are resistance sensors, while the film thickness sensor functions as a capacitive transducer. Experiments were carried out with ground and hobbed gears. The measurements are repeated after the tooth flank has been polished. The differences of the measured values for the ‘rough’ and ‘smooth’ surfaces are used for comparisons between differently machined surfaces.

An EHD simulation programme has been developed which calculates film thickness and contact pressure, also taking surface roughness into account.
Prediction of lubrication regimes of concentrated contacts
Authors: Schipper D. J. , Vroegop P. H. , De Gee A. W. J.
Published: July 2006

Friction experiments are performed on lubricated concentrated contacts (LCCs) to obtain the transitions EHL‐ML and ML‐BL as a function of the operational conditions under which these contacts operate. A transition diagram is developed to determine the lubrication mode of an LCC as a function of the operational conditions. In this investigation the LCCs operated macroscopically in the lubricants' liquid state regime.
An investigation of the effects of some motor oil additives on the friction and wear behaviour of oil‐soluble organomolybdenum compounds
Authors: Wei D. , Song H. , Wang R.
Published: July 2006

The compatibility of oil‐soluble organomolybdenum compounds with some motor oil additives (detergent, dispersant, rust inhibitor and ZDDP) has been investigated on a four‐ball machine and a SRV tester. Preliminary results indicated that a combination of two agents might have either synergistic or antagonistic effects on the friction and wear performance of the organomolybdenum compounds, although many combinations were shown to be synergistic. The interactions between two agents were primarily determined by the additive types, additive concentrations and test temperatures.

It was also found that the presence of calcium sulphonate detergent was particularly beneficial to molybdenum dithiophos‐phate and molybdenum dithiocarbamate in terms of friction reduction and wear reduction at temperatures in a certain range. The induction period of the organomolybdenum compounds was also reduced. Surface analysis results suggested that the synergistic effects were closely related to the formation of thick films, which were rich in molybdenum and sulphur, on rubbing surfaces.
Resistance of ashless dispersant additives to oxidation and thermal decomposition
Authors: Bartha L. , Hancsok J. , Bobest E.
Published: July 2006

Ashless dispersants of the type of alkenyl‐succinic anhydride derivatives were prepared. The resistance of these compounds to oxidation and thermal decomposition was investigated by thermoanalytical methods. Results were compared to those obtained in a panel coking test of these additives at 300°C in a multifunctional package. It was found that data obtained by DSC could be used for rating the stability of polyisobutenyl‐succinimides against thermo‐oxidation.
An analysis of heat transfer in the thin‐layer transducer used for the measurements of EHD contact parameters
Authors: Hofman S. , Bartz W. J.
Published: July 2006

Thin‐layer transducers, which are mainly used for the measurement of the EHD contact parameters, have to be attached to an isolating layer separating it from the steel roller. The isolating layer, made of SiOx or Al2O3, disturbs heat flow in relation to the real contact. This paper presents a solution for the system of two heat conduction equations for a two‐layer body: SiOx‐steel. The boundary conditions reflect the real situation during the measurements carried out by means of these transducers. The solution was obtained for an assumed temperature distribution of the isolating layer surface. Computation results for two different temperature distributions of the surface and for various values of the SiOx‐layer thickness are also presented.
The performance of some antiwear additives and interference with other additives
Authors: Palacios J. M.
Published: July 2006

This paper reports work on the evolution of films formed by some antiwear additives. Between having an additive solution in a fresh lubricant and the actual deposition of protective films on the rubbing surfaces there is a gap during which the normal actions of a given additive may be affected by the presence of another additive.

Film thickness is one of the most important parameters affecting wear. Interference between additives can change the chemical composition and the thickness of the films formed and, consequently, can modify the antiwear properties of the original additive.
Interaction of different types of additive with oil‐soluble metal salts ‐ homogeneous catalysts of oxidation
Authors: Vipper A. B. , Glavati O. L.
Published: July 2006

The interaction of zinc dithiophosphate and phenolic antioxidants with metal naphthenates, mainly with copper naphthenate, has been investigated. A complex compound is formed on the interaction of zinc dithiophosphate with copper naphthenate; this has a noticeable influence on the antioxidation effectiveness of zinc dithiophosphate. The possibility of increasing the antioxidising action of zinc dithiophosphate through its combination with a copper passivator is shown. The formation of complex compounds on the interaction of phenolic antioxidants with copper naphthenates depends on the structure of these additives.
Effect of surface roughness on the lubrication properties of the piston ring and cylinder of an engine, and calculation of lubrication and power loss analysis of piston‐ring pack of a S195 diesel engine
Authors: Gui C. L. , Liu K.
Published: July 2006

The effect of surface roughness on lubrication of piston ring and cylinder is examined. In particular, the temperature effect is considered, and a model proposed to overcome shortcomings in the previous mathematical model. Further, film thickness was measured by transducer capacitance method in a S195 diesel engine. The results found are consistent with theoretical results. In addition, the authors show quantitatively the value of friction power losses of the ring package of a S195 diesel engine.
Antiwear actions of additives in solid dispersion
Authors: Morizur M. F. , Teysset O.
Published: July 2006

In this paper we compare the action mechanisms of different ‘non‐soluble’ additives: a dispersion of potassium triborate and overbased detergents formed by calcium carbonate, or borate aggregates dispersed by a detergent. These additives act by producing a deposit issued from their mineral phase, on the friction surface. With the potassium triborate, a solid film of borate, bound to the metal, is only detected on a negatively‐polarised surface or in conditions of severe wear when friction surfaces have been activated by abrasion. On the contrary, with the overbased detergent, a solid film is always detected on the friction surfaces, even without activation by abrasion. This additive is decomposed in the contact zone by the effect of the elevated pressure. The present study shows that the method of placement in suspension of the inorganic phase by the detergents is important. It offers the advantage of forming deposits only in the friction zone, instantly and independently of the type and state of the friction surface.
Carbonyl peak index technique in the study of lubricant oxidation
Authors: Maduako A. U. C. , Ofunne G. C. , Ojinnaka C. M.
Published: July 2006

A technique known as the Carbonyl Peak Index (CPI) is used to assess the relative oxidation stabilities of two competing grades of commercial automotive crankcase oils, their base oils, and the oxidation characteristics resulting from oil/metal interactions. The CPI provided empirical data from the infrared spectra which enabled a more lucid explanation of the oil soluble acidity and sludge deposition characteristics of the oils. A combination of these parameters has confirmed that the hydrocarbon type composition of the oils gave some stability to the fully formulated monograde oil. Consequently, the monograde base oil was found to possess a greater stability towards oxidation than the multigrade base oil under the conditions of test. However, the fully formulated oils were found to be more stable than the base oils, mainly due to the added antioxidants. Metals in the oils acted as antioxidants initially, but later turned to pro‐oxidants. The reversal of metal action from inhibition to autooxidative catalysis was also found to be base‐oil hydrocarbon‐type dependent and this has been related to the natural antioxidant capacity of the oils.
The influence of base oil properties on the efficiency of action of ZDDP‐type additives
Authors: Kulczycki A. , Kajdas C.
Published: July 2006

This paper deals with the analysis of the influence of base oil viscosity on the ability of ZDDP‐containing lubricants to form protective layers (especially antiwear layers). The chemical structure of additives used was characterised according to their thermal stability, determined by differential scanning calorimetry (DSC). The additives were added to base oils of various viscosities. The prepared lubricants were tested using a four‐ball machine, and analysed by DSC.

The relationships between base oil viscosity and seizure load (Pt), weld load (Pw) and DSC test results are presented and discussed. The mechanism of interaction between ZDDP and the base oils was analysed by the use of a mathematical model.
Effect of amines on the antiwear properties of P‐containing compounds as oil additives
Authors: Wan Yong , Liu Weimin , Ren Tianhui , Xue Qunji
Published: July 2006

This paper reports a study on the effects of concentration and the molecular structure of amines on the antiwear properties of TBP, TCP and TBPi, evaluated with a four‐ball machine. It was found that amines reduce the antiwear properties of P‐containing additives in the order primary>secondary>tertiary amine, and a critical amine concentration exists at which P‐containing additives lose their antiwear properties. XPS analysis indicated that the competitive adsorption of amines onto the rubbed surface causes a reduction of the antiwear properties of P‐containing additives.
Studies on additive‐additive interactions: Effects of dispersant and antioxidant additives on the synergistic combination of overbased sulphonate and ZDDP
Authors: Ramakumar S. S. V. , Aggarwal Neelam , Rao A. Madhusudhana , Sarpal A. S. , Srivastava S. P. , Bhatnagar A. K.
Published: July 2006

A strong synergism between overbased sulphonate (OBS) and zinc dialkyldithiophosphate (ZDDP) in a proven diesel engine oil formulation has been reported in an earlier communication.1 In continuation of these studies, the effect of different types of dispersant, of varying nitrogen content, and an antioxidant, on a synergistic combination of OBS‐ZDDP has been investigated. Both detergency and dispersancy of the optimised formulation were improved with high nitrogen‐content dispersants, which also increased strongly the wear tendencies. The antioxidant, though it improved detergency, did not show any positive effect on antiwear performance. Detailed IR and 31p‐NMR spectroscopic analyses on interactive additive pairs, namely, ZDDP‐PIBS and ZDDP‐antioxidant, indicated the formation of association complexes and hydrogen bonding respectively.
The performance and antiwear mechanism of S‐containing organic borate as an oil additive
Authors: Liu Weimin , Jin Zhishan , Xue Qunji
Published: July 2006

A sulphur‐containing organic borate (BS‐2) was prepared. Its friction and wear properties when added to n‐tetradecane, and the effect on wear of addition of dodecyl amine to the synthesised S‐containing borate oil, were measured using a Timken test machine. The results were compared with those of tridodecyl borate, and a combination of tridodecyl borate and sulphurised cotton seed oil. X‐ray Photoelectron Spectroscopy (XPS) was used to examine the rubbed surfaces of the test blocks, while Scanning Electron Microscopy (SEM), Energy Dispersion Analysis of X‐ray (EDAX) and X‐ray Diffraction (XRD) were used to study the wear debris.

It is found that S‐containing organic borate exhibits a poorer antiwear property than tridodecyl borate but, with the addition of dodecyl amine to the S‐containing borate, its antiwear property can be improved. XPS analyses indicate that sulphur on the rubbed surfaces exists in the forms of organic sulphide and FeSO4, and the addition of amine reduces the adsorption and reaction of sulphur to the rubbing surfaces. SEM analyses revealed that the wear debris was in powder form, and the EDAX and XRD analyses indicated that iron sulphide, iron oxide and elemental iron were contained in the wear debris. A corrosive wear mechanism of steel test blocks lubricated by S‐containing organic borate is proposed.
Tribochemistry and the development of AW and EP oil additives — a review
Authors: Xue Qunji , Liu Weimin
Published: July 2006

The antiwear (AW) and extreme pressure (EP) properties of chlorine, sulphur, phosphorus‐containing organic compounds and zinc dialkyldithiophosphate (ZDDP) oil additives are affected greatly by their reactive ability to the metal surface, as well as by the chemical composition, chemical state, physical and mechanical properties of the protective films formed. Over four decades, research has taken place on boundary lubrication, and a much better understanding of the AW and EP action mechanism of one additive by itself in base oil has been obtained, and much more knowledge on the relationship between wear and decomposition of additives, adsorption and reaction of the additive or its decomposed products with metal, has been gained. A series of analytical methods and a great number of modern surface analytical tools have been set up and used for research in this area. The problems and some suggestions for the future study on boundary lubrication of oil additive are proposed.
An infrared analysis method to determine the aromatic carbon content of mineral lubricant base oils based on correlation with carbon‐13 NMR aromaticities
Authors: Van De Ven Adri M. C. , Jansen Leen , Heijer Joop Den
Published: July 2006

A widely used method to determine base oil aromaticity was introduced by G. Brandes in 1956 and is based on a correlation between the infrared aromatic absorption band at 1610 cm−1 and the aromaticity determined by the n‐d‐M method. Accurate and absolute aromaticities can be measured by carbon‐13 NMR but, infortunately, this technique is not suitable for routine analysis.

The aromaticities measured by NMR are almost invariably significantly lower than those obtained by Brandes' method. In this study, the areas of the infrared aromatic bands at 1610 and 815 cm−1 of over 70 base oils with aromaticities ranging from 1–16% were correlated by multilinear regression with their carbon‐13 NMR aromaticities. An equation to calculate the aromaticity from infrared absorptions was derived. These aromaticities show an excellent match with carbon‐13 NMR data. This new infrared method can be applied as a fast and convenient base‐oil quality control tool.
The effect of contamination particles on lithium grease deterioration in sealed ball bearings
Authors: Jin Xue
Published: July 2006

With advanced analytical methods, the effects of four kinds of contamination particles, including Fe, Cu, and MoS2 powders, on lithium grease deterioration in sealed ball bearings has been studied. As the deterioration process of grease at high temperatures is triggered by chemical factors, so a number of tests have been conducted at 125°C to investigate its effect upon the deterioration process of grease, with various particles, under the condition of a bearing speed of 3000 r/min. As well as the deterioration phenomena, the mechanism of the deterioration of lithium grease in a sealed bearing with particles is also discussed in detail.
A spectroscopic study of a copper surface under boundary lubrication: I. Chemisorbed stearic acid multilayers
Authors: Hu Zu‐Shao , Wang Pu Sen , Hsu Stephen M.
Published: July 2006

The thickness of chemisorbed stearic acid films on copper surfaces was deduced by Fourier transform infrared (FTIR) spectroscopy and Auger electron spectroscopy (AES). The chemisorption was detected by FTIR from the carboxyl (COO) asymmetric stretching band at 1585 cm−1. Multilayer growth was observed by monitoring the intensity increase in the asymmetric CH2 stretching mode at 2915 cm−1. The growth of the chemisorbed layer was found to depend on the concentration of the stearic acid/hexadecane solution. The chemisorption kinetic profile had a step‐function due to the change in the number of layers. High carbon concentration in Auger spectroscopic characterisation indicated that the surface was coated with a stearic acid film. AES depth profiling analysis supports this step‐function model and agrees well with the FTIR results.
The energy pulse: A new wear criterion and its relevance to wear in gear teeth and automotive engine valve trains
Authors: Plint M. A. , Alliston‐Greiner A. F.
Published: July 2006

The paper follows an earlier study in which the various standard test procedures for assessing the extreme pressure and anti‐wear properties of lubricants were classified and evaluated in terms of a number of parameters.

The significance of the frictional heating energy was apparent and a new parameter, the energy pulse, was proposed. This concept has been further developed in the present paper and applied to an analysis of contact conditions and patterns of wear in gears and valve trains.
Antioxidant properties of engine oil detergent additives
Authors: Vipper A. B.
Published: July 2006

The antioxidant properties of engine calcium sulphonate, phenate and salicylate detergent additives were investigated. Their influence on engine oil oxidation both in the presence of metallic copper, oil‐soluble copper compounds, and without any catalyst, was studied. The influence of the detergent type and its basicity on oil antioxidant properties was determined. The specific influence of the co‐operative action of detergent additives and zinc dithiophosphate on the antioxidant properties of engine oil formulations with these additives was established. The results obtained revealed various new patterns concerning the oil oxidation process, and allowed us to characterise the process of depletion of detergent additives during oil ageing.
Tribological performance and mechanism of action of overbased detergents
Authors: Vipper A. B. , Cook S. J. , Karaulov A. K. , Moreton D. J. , Mischuk O. A. , Leahy R.
Published: July 2006

The antifriction properties of calcium phenate‐, sulphonate‐ and alkylsalicylate‐type detergent additives were investigated. The influence of the detergent type and its basicity on engine oil antifriction properties was determined. The tribological performance of different detergents was characterised by laboratory methods. Auger spectroscopy was used for surface layer composition and thickness determination. The experimental data allowed the mechanism of action and the tribological performance characteristics of overbased detergents to be more precisely identified.
Biotribology: Friction, wear, and lubrication of natural synovial joints
Authors: Furey Michael J. , Burkhardt Bettina M.
Published: July 2006

Studies have been carried out over the past several years to explore possible interconnections between tribology — the study of friction, wear, and lubrication — and arthrology, more specifically, mechanisms of synovial joint lubrication and degeneration. The focus of this paper is on the tribological behaviour of natural and so‐called ‘normal’ synovial joints. A separate paper deals with possible connections between tribology and degenerative joint disease (e.g., osteoarthritis).

The purpose of this paper is fourfold: (1) to present a summary of salient work on mechanisms of synovial joint lubrication; (2) to review the key findings of our in vitro wear studies made with bovine articular cartilage; (3) to discuss the significance of the cartilage wear studies in relation to existing joint lubrication theories; and (4) to describe a new device being used for studies of cartilage‐on‐cartilage deformation, friction, wear and damage under in vitro conditions.
Antifriction properties of calcium phenate‐type detergents used in marine cylinder lubricants
Authors: Vipper A. B. , Cook S. J. , Karaulov A. K. , Leahy R.
Published: July 2006

The antifriction properties of calcium phenate‐type detergents of different lubricity were investigated by laboratory methods. Simulation of the operating environment in super‐long‐stroke marine diesel engines was achieved using concentrated sulphuric acid. The influence of the tested additives on engine oil antifriction properties was determined after their being mixed with acid. The tribological performance of oil samples with 50 and 70 TBN values was characterised by testing on a friction machine, and by thickness determination of friction surface layers using Auger spectroscopy. It was found that the effectiveness of antifriction action of the detergents tested depends on the thermal stability of the lubricating layers, the temperature at which the destruction of the boundary lubricating layers occurred, and the thickness of secondary structure layers in the metal surface of the friction pairs.
Antiwear and extreme‐pressure additives in lubricants
Authors: Papay A. G.
Published: July 2006

This paper reviews the chemistry, mechanisms, and interactions of antiwear and extreme‐pressure additives used to supplement the performance of lubricants. Some examples with respect to their application are also given.
The non‐Newtonian effect of temperature on hydrodynamic lubrication failure
Authors: Guangjun Zhang , Ping Huang , Shizhu Wen , Huirong Meng
Published: July 2006

The influence of temperature on the rheological characteristics of lubricants has been investigated by analysing the viscosity‐temperature relationship and energy equation of lubricants. The constitutive equation, which describes the non‐Newtonian properties of lubricants caused by thermal effects, is founded and coupled with equations of continuity and momentum of the fluid to calculate the load‐carrying capacity in hydrodynamic lubrication. The numerical solutions show that lubricants have ultimate shear strength as a result of the non‐Newtonian effect of temperature, which leads to the oil film having limiting load‐carrying capacity. The mechanism of film failure in hydro‐dynamic lubrication is also studied preliminarily in this paper.