Showing papers in "Journal of Synthetic Lubrication in 2000"
TL;DR: In this article, four research areas at the NASA Glenn Research Center involving the tribology of space mechanisms are highlighted, including soluble boundary lubrication additives for perfluoropolyether liquid lubricants, a Pennzane dewetting phenomenon, the effect of ODC-free bearing cleaning processes on bearing lifetimes and the development of a new class of liquid lubricant based on silahydrocarbons.
Abstract: Four research areas at the NASA Glenn Research Center involving the tribology of space mechanisms are highlighted. These areas include: soluble boundary lubrication additives for perfluoropolyether liquid lubricants, a Pennzane dewetting phenomenon, the effect of ODC-free bearing cleaning processes on bearing lifetimes and the development of a new class of liquid lubricants based on silahydrocarbons.
47 citations
TL;DR: In this paper, three commercially available hydraulic/transmission lubricants based on rapeseed oil have been investigated for their lubricating properties: coefficient of friction, scuffing-load capacity, and pitting resistance.
Abstract: Three commercially available hydraulic/transmission lubricants based on rapeseed oil have been investigated for their lubricating properties. The coefficient of friction, scuffing-load capacity, and pitting resistance were evaluated, and the results compared with a corresponding commercial mineral-based oil.
The results showed in general a substantially lower coefficient of friction and better pitting resistance for rapeseed-based oils than for the mineral oil. Scuffing load capacity was, with one exception, the same for all oils. As a result of lower shear stresses during contact, and a higher viscosity index, the temperatures in the gearbox were lower for the rapeseed oils tested than for the mineral oil. Insufficient antiwear behaviour at high loads was found to be a major drawback of these vegetable oils.
44 citations
TL;DR: In this article, the synthesis of esters, which is a reversible reaction of acid + alcohol + ester + water, usually involving a catalyst, has been studied and the effect of ester structure on rate of hydrolysis, in terms of resonance effects and steric effects.
Abstract: 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.
35 citations
TL;DR: In this article, the authors compared the tribological properties of commercially available rapeseed- and mineral-based oils, rapeseed and mineral base oils, and these base oils mixed with two additives for improving lubricity.
Abstract: The use of rapeseed-based lubricating oils has become more widespread in recent years. When these oils have been tested for their tribological properties, some imperfections have been found, especially in conditions of highfrequency and low-amplitude oscillating movements. In the present work, we compare the tribological properties of commercially available rapeseed- and mineral-based oils, rapeseed and mineral base oils, and these base oils mixed with two additives for improving lubricity. The results are compared for a wide range of contact pressures.
33 citations
TL;DR: In this paper, the authors have developed polyglycol-chemistry-based products that fulfil the application requirements and are also environmentally friendly, based on the Blue Angel formulations for two water-soluble poly glycol grades (ISO 22 and IS 0 46).
Abstract: Polyglycols are used in a wide range of applications, including lubrication. Many advantageous properties can be obtained for lubricant applications by manipulating the four variables in polyglycol preparation: the initiator, the alkylene oxides, the molecular build-up, and the mole weight. However, it has long been believed that it would not be possible to combine these properties with a good environmental profile of high biodegradability and low aqueous toxicity. Development work at the authors' laboratory has resulted in polyglycol-chemistry-based products that fulfil the application requirements and are also environmentally friendly. Assessment by the Umwelt Bundes Amt has led to a statement of suitability for Blue Angel formulations for two water-soluble polyglycol grades (ISO 22 and IS0 46). Environmentally-friendly watersoluble polyglycol base stocks currently includes the range ISO 10 to ISO 100. The development of environmentally friendly water-insoluble and oil-soluble polyglycols is under way.
24 citations
TL;DR: In this paper, the synthesis and characterisation of three lubricating greases based on animal bone fat, cottonseed soapstock, and a mixture of them both was reported, which were assessed in accordance with standard NLGI grades and Egyptian standards, and revealed that the synthesised greases have significant yield stress at normal operating temperature and good flow properties.
Abstract: This paper reports on some work concerned with the synthesis and characterisation of three lubricating greases based on animal bone fat, cottonseed soapstock, and a mixture of them both. The physico-chemical properties of these fats were established and showed them to be good thickeners in the preparation of different types of greases. It was shown that the growth of the soap structure and grease consistency depend on the type of fat as well as on the viscosity of the lubricating oil in the grease formulation. The greases so synthesised were assessed in accordance with standard NLGI grades and Egyptian standards. Their rheological and thermal behaviour was studied, which revealed that the synthesised greases have significant yield stress at normal operating temperature and good flow properties. It was concluded that the above mentioned fat by-products are suitable for producing greases.
10 citations
TL;DR: In this article, the authors developed a series of heterocyclic compounds for use in turbine aviation oils as antioxidant and anticorrosion additives, which were tested against DODPA, an existing aviation fluid additive, and were found to offer comparable behaviour in initial tests.
Abstract: This paper reports on work by the authors to develop a series of heterocyclic compounds for use in turbine aviation oils as antioxidant and anticorrosion additives. First, the new compounds were synthesised, and twenty-eight candidate additives were developed. These were tested for their antioxidant and anticorrosion properties, and from these results three were found to exhibit better behaviour than the others. These three were then tested against DODPA, an existing aviation fluid additive, and were found to offer comparable behaviour in initial tests.
10 citations
TL;DR: In this article, the authors compared data on the oxidation stability of turbine turbine oils obtained using the FTM 791, method 5308 test, at various temperatures, and PDSC experimental data, to standard class oils (STD).
Abstract: Thermo-oxidative stability in aerospace turbine oils is an important criterion. A new category (HTS) of turbine oil has been introduced, and the present work compares data on the oxidation stability of HTS oils obtained using the FTM 791, method 5308 test, at various temperatures, and PDSC experimental data, to standard class oils (STD). PDSC has become established in recent years as an effective means with which to establish the thermo-oxidative stability of oils. The purpose of the present work was to find out whether PDSC could identify HTS oils correctly, and also to increase our understanding of some of the chemical processes behind the test results. Analogies in the degradation of the oligomer antioxidants have been confirmed by MALDITOF mass spectra.
7 citations
TL;DR: In this paper, a transesterification reaction in the presence of powdered calcium oxide which acts as a catalyst was used for the synthesis of simple dicarboxylic esters and complex esters.
Abstract: A new method of manufacturing simple dicarboxylic esters and complex esters has been developed. This method is based on a transesterification reaction in the presence of powdered calcium oxide which acts as a catalyst. Commonly accessible raw materials, namely, dimethyl adipate, 2-ethylhexanol, neopenthyl glycol, and trimethylolpropane were used for the synthesis of the esters. The methanol formed in the transesterification reaction was continuously removed by azeotropic distillation with isooctane. The possibility of producing complex esters with different viscosities and polarities by modification of their chemical structure was studied.
7 citations
TL;DR: In this paper, the synthesis of tetraesters with a mixed structure of pyromellitic dianhydride, and their characterisation as potential base oils is discussed. But the results of the synthesis are limited and the potential for viable products with a wide range of viscosity values has been examined.
Abstract: The present paper deals with the synthesis of some tetraesters with a mixed structure of pyromellitic dianhydride, and with their characterisation as potential base oils. These esters are made on the basis of a long branched aliphatic alcohol, such as isotridecanol, and an alcohol with aromatic content, such as 2-phenoxy-ethanol. The variation of the principal properties as a function of both the length of the aliphatic chain introduced by the aliphatic alcohol, and the aromatic content introduced by the aryl-alkyl alcohol has been assessed and the potential for viable products with a wide range of viscosity values has been examined. The enhanced aryl content is shown to induce superior thermal behaviour. These products present good test results and, thereby, demonstrate their versatility.
7 citations
TL;DR: In this article, the essential requirements of environmentally adapted lubricants, i.e., chemical composition, eco-toxicity, biodegradability, bio-accumulation, and eco-labelling schemes, and life cycle analysis, are reviewed.
Abstract: The requirement for environmentally adapted lubricants has begun to play an increasingly important role in many industrial applications, particularly in the last two decades. The present-day requirements for biodegradable and eco-friendly lubricants imply that lubricants have properties that can minimise, if not eliminate, negative environmental impact, such as contamination of soil and water, caused by lost lubrication, leakage and accidents. The dominant factors that have a direct impact on the environment and which characterise the lubricant and its chemical composition, are toxicity, bio-accumulation and biodegradability. Biodegradability is perhaps the most important factor which determines the fate of lubricant in the environment.
Various commercial, governmental, and regulatory initiatives exist that protect the interests of the consumer. Life cycle analysis can help in assessing the total environmental impact of lubricants. This paper reviews the essential requirements of environmentally adapted lubricants, i.e., chemical composition, eco-toxicity, biodegradability, bio-accumulation, and eco-labelling schemes, and life cycle analysis.
TL;DR: In this article, the main categories of hydraulic fluids, including environmentally friendly fluids, are discussed in an overview of the state of technology in this area, and current governmental regulation, and the properties required of environmentally adapted fluids, and an appraisal of the current practices in various countries are also given.
Abstract: 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.
TL;DR: In this article, a high-temperature polymer, polyethersulphone (PES), was selected for some adhesive wear studies, along with two PES composites containing 18% glass-fibre (GF) reinforcement and two solid lubricants, i.e., PTFE and MoS2 (2% each).
Abstract: High-temperature polymers are generally preferred for those tribology applications where cost is secondary and performance is the primary consideration. Since frictional heat dissipation limits the usefulness of polymers because of their poor thermal conductivity, high-temperature polymers are preferred in applications which have harsh operating conditions. In this paper, a high-temperature polymer, polyethersulphone (PES), was selected for some adhesive wear studies, along with two PES composites containing 18% glass-fibre (GF) reinforcement and two solid lubricants, i.e., PTFE and MoS2 (2% each). Adhesive wear studies of these materials on two pin-on-disc machines indicated that neat PES was not a good tribo-material. However, incorporation of GF and solid lubricants enhanced the wear performance by an order of two. PTFE was found to behave better than MoS2. However, after long sliding duration both the lubricants performed almost equally well. The topography of the surface of the pins and the disc was studied using SEM to investigate the wear mechanisms.
TL;DR: In this article, short carbon-fibre reinforced composites of some heat resistant polymers, such as polyetherimide, polyethersulphone, polyamide 6,6, polyetheretherketone, and polytetrafluoroethylene, were selected to explore the potential of cryo-treatment.
Abstract: Cryo-treatment, a bulk modification technique, is fast emerging as a way with which to improve the wear resistance of metals. This technique has also shown the ability to enhance significantly the abrasive wear performance of some polymers and their short glass-fibre reinforced composites. In this work, short carbon-fibre reinforced composites of some heat resistant polymers, such as polyetherimide, polyethersulphone, polyamide 6,6, polyetheretherketone, and polytetrafluoroethylene, were selected to explore the potential of cryo-treatment. The selected materials were cryogenically treated by cooling them to the temperature of liquid nitrogen. The abrasive wear tests were carried out at ambient temperature in single pass conditions at various loads, on a pin-on-disc machine, using silicon carbide paper as a counterface. The investigations revealed that this technique has definite potential to increase the wear performance of carbon-fibre reinforced composites. An increase in hardness due to cryo-treatment was thought to be responsible for an observed improvement in wear performance. However, the extent of improvement in the wear performance was not matched by an increase in the hardness value. Scanning electron microscopy proved useful in examining the morphological changes in the composites due to cryo-treatment.
TL;DR: Examples of CONCAWE test results for a number of base fluids and formulated products are given, and the extent to which a product can be removed from the natural environment by biodegradation is compared with those obtained in a ‘ready biodegradability’ test.
Abstract: Information on the biodegradability of an oil product (or its components) is needed for classification and labelling purposes. The extent to which a product can be broken down by microbial attack is usually determined using a ‘ready biodegradability’ test (e.g., OECD 301 Test Guidelines). However, these methods are stringent screening tests and can often underestimate the extent to which a product can be removed from the natural environment by biodegradation. CONCAWE (the European oil companies’ organisation for environment, health and safety) has recently developed a test for determining the potential (or ‘inherent') biodegradability of oil products. This is often more useful for assessing the likely impact of an oil product in the event of its release into the environment. This paper gives examples of CONCAWE test results for a number of base fluids and formulated products, and compares these results with those obtained in a ‘ready biodegradability’ test. Guidance is given on the applicability of data that has been obtained using the CONCAWE method.
TL;DR: In this paper, the results of a characterisation of heavy alkylated benzenes (HAB) using multipulse NMR spectroscopy are presented, in which four commercial samples of HAB have been characterised in detail in terms of various structural parameters, such as percentage aromatic carbon (Ca), degree of aromatic substitution, average alkyl chain length, type of alkyls chain and their proportions.
Abstract: In this paper, the results of a characterisation of heavy alkylated benzenes (HAB) using multipulse NMR spectroscopy are presented. Four commercial samples of heavy alkylated benzene have been characterised in detail in terms of various structural parameters, such as percentage aromatic carbon (Ca), degree of aromatic substitution, average alkyl chain length, type of alkyl chain and their proportions. Three of the HAB samples were very similar in structure, whereas, in the fourth, the structures present were entirely different. The latter had an abundance of 2-phenyl alkane-type structures, and did not contain methyl substituted tetralin or naphthalene type molecules. The influence of the structures on lubricating oil properties, including viscosity index, pour point, and viscosity, as well as FreonTM floc point, are also discussed.
TL;DR: In this article, two ester bases were selected for further testing, a pentaerythritol esterified with monocarboxylic acids, and a polyalkyleneglycol similarly esterifer with methyl ester transesterification in the presence of basic catalysts.
Abstract: The aim of the present work was to produce inexpensive synthetic lubricants, compatible with R-134a, using waste carboxylic acids as the starting point. After initial synthesisation of some candidate materials, the suitability of the synthesised products was first evaluated by their chemical and physical properties including thermostability. Two ester bases were selected for further testing — a pentaerythritol esterified with monocarboxylic acids, and a polyalkyleneglycol similarly esterified with monocarboxylic acids C4—C6. The oil bases selected were tested for their corrosion effect on metals. The pentaerythritol ester offered the most advantageous properties in these tests. The results of the laboratory tests have been corroborated by trials conducted on real refrigerating compressor systems. In addition, the synthesis of base oils by methyl ester transesterification in the presence of basic catalysts has been examined.
TL;DR: In this article, the effects of degradation on film-forming properties were investigated in the light of the idea that degradation of an ester lubricant can produce two different types of product which have opposing influences on film forming properties: smaller, polar molecules, such as acids, which may result in a decrease in effective pressure-viscosity coefficient, and larger, bulky molecules such as sludge, which result in an increased pressure-vicosity coefficient.
Abstract: The film thicknesses of two polyolester degraded oils were measured over a wide range of temperatures to investigate the influence of degradation on film-forming properties. The results have been interpreted in the light of the idea that degradation of an ester lubricant can produce two different types of product which have opposing influences on film-forming properties. One is the formation of smaller, polar molecules, such as acids, which may result in a decrease in effective pressure—viscosity coefficient. The other is the formation of larger, bulky molecules such as sludge, which result in increased pressure—viscosity coefficient. The effective pressure—viscosity coefficient decrease with degradation of the oil thus is made up of an earlier stage involving a series of reactions, followed in a later stage by an increase.
TL;DR: A brief review of the oils, fuels, additives, and other industrial products being derived from non-food crops in France, and the potential market for them can be found in this paper.
Abstract: A brief review of the oils, fuels, additives, and other industrial products being derived from non-food crops in France, and the potential market for them.
TL;DR: In this article, a novel ashless (metal-free) friction modifier with anti-wear properties, specifically designed for aqueous systems, is reviewed, which does not contain phosphorus, sulphur, or halogens.
Abstract: 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.