Phosphate esters with a complex structure of an alkyl‐aryl type considered as base oils

This paper presents results of work carried out to produce phosphate esters of the alkyl‐aryl type. Three new triesters of mixed structure have been synthesised using a special alcohol with an aryl content, e.g., 2‐phenoxy ethanol, and a very long branched alcohol, e.g., isotridecanol. The influence of the aryl content and the effect of the long aliphatic chain on the main tribological properties have been investigated.     

Pyromellitic esters with enhanced aromatic content and a mixed structure considered as tribological fluids

The paper presents results concerning research carried out in order to produce synthetic ester oils with superior thermal resistance and adequate tribological properties. Three series of new tetraesters with mixed structure have been synthesized with pyromellitic dianhydride as the basic acid structure; as for the alcoholic part, large normal or branched aliphatic alcohols have been used along with a special alcohol of aliphatic-aromatic structure, namely 2-phenoxyethanol. By varying the molar relationship between the two alcohols as well as by modifying the structure and the length of the aliphatic alcohol, it has been possible to obtain products with variable properties. Testing has shown this system to be highly flexible and a wide range of values was observed. The synthetic oils created in this way are especially remarkable with respect both to their viscosities, which offer an extended range of values, and to their particularly high thermal stability. This revised version was published online in August 2006 with corrections to the Cover Date.     

New synthetic esters with a complex structure considered as tribological fluids

The paper presents results concerning synthesis and characterisation as lubricant fluids of some esters of different monocarboxylic acids with variable chain length, along with aliphatic‐aromatic complex alcohols and/or with superior alcohols (exclusive of aliphatic). The monocarboxylic acids taken into account were n‐butyric, n‐octanoic and oleic, respectively, while the alcohols considered were isodecyl and isotridecyl as purely aliphatic, and 2‐phenoxy‐ethanol, 2‐[(o‐sec‐butyl)phenoxy]ethanol and 2‐[(p‐nonyl)phenoxy]ethanol, as part of the complex aliphatic‐aromatic alcohols group. Under these circumstances, it became possible to study the influence of the structure on the main physico‐chemical properties of these synthetic oils as well as on their tribological representative features. The results recorded certified the validity of the proposed research programme. Copyright © 2009 John Wiley & Sons, Ltd.     

New citric esters with aromatic content and a complex structure considered for use as tribological fluids

This paper presents the results of research carried out to produce synthetic ester oils with a mixed structure, based on citric acid, with beneficial tribological properties and potential biodegradability. Two series of unsymmetrical triesters have been synthesised by varying the molar relationship between aliphatic alcohols from C₁, to C₁₃ along with an alcohol of a complex alkyl‐aryl structure, namely 2‐[(p‐nonyl)phenoxy]ethanol. The variation of the principal properties as a function of the length of the aliphatic chain introduced by the aliphatic alcohol and the aromatic content introduced by the alkyl‐aryl alcohol has been assessed. The wide range of viscosities of these triesters demonstrates their versatility, and the natural citric acid origin holds potential for their having good ecological characteristics.     

New unsymmetrical complex diesters of adipic acid considered as tribological fluids

The paper presents results concerning the synthesis and characterisation of some unsymmetrical diesters of adipic acid with a mixed, complex structure in order to produce synthetic ester oils with specific tribological properties. These complex diesters have been synthesised by taking into account medium and superior aliphatic alcohols, such as n‐butanol, n‐hexanol, 2‐ethyl‐hexanol, isodecanol and isotridecanol along with special alcohols of a complex alkyl–aryl nature, namely 2‐phenoxy‐ethanol, 2‐([o‐sec butyl] phenoxy) ethanol and 2‐([p‐nonyl] phenoxy) ethanol, respectively. By varying the length of the aliphatic alcohols and also by modifying the length and position of the alkyl pendant group on the aromatic ring of the complex alkyl–aryl alcohols, three series of products have been realised. On the basis of this programme, it has been possible to obtain fluid products that show valuable tribological features with adequate and versatile characteristics. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of the chemical structure of fluorinated esters on the tribological properties of a steel‐on‐steel system

The effect of the chemical structure of fluorinated esters on the friction and wear behaviour of a steel‐on‐steel system was investigated. The friction and wear testing of a steel disc sliding against a counterpart ball of the same steel was carried out using an Optimal SRV oscillating friction and wear tester. The chemical features of the worn steel surfaces were analysed by means of X‐ray photoelectron spectroscopy, and the morphologies and elemental compositions of the worn steel surfaces observed and determined using scanning electron microscopy. The results indicate that a fluorinated ester with methylene groups that are not substituted by fluorine in the acid structure gives the best friction‐reducing behaviour and a keto‐ester shows the best antiwear properties.     

Synthetic adipic complex tetraesters as eco‐friendly lubricants

The paper presents results concerning the synthesis and characterisation as lubricants with biodegradability potential of some complex tetraesters realised on the basis of adipic acid and different glycols such as (mono) ethylene, 1,3‐propylene, 1,4‐butylene, 1,5‐pentamethylene, 1,6‐hexamethylene, diethylene and triethylene glycol, respectively, along with oleic acid used, considered as an end, final segment or as a capping element. On the basis of a regular alternation or successive distribution principle of the polar and nonpolar chemical functions equally distributed, shared out on the length of a sufficient, satisfactorily long, large molecule, valuable synthetic complex tetraester lubricants considered as eco‐friendly base oils with biodegradability potential were performed. These products showed very good tribological properties, such as high viscosity indices and high flash points, and also very good lubricity features. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthetic aluminium complex grease: A tribological evaluation using a four‐ball test

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.     

Tribological characteristics of bisphenol S bis(diphenyl phosphate) as a high‐performance antiwear additive in lubricating greases at elevated temperature

Bisphenol S bis(diphenyl phosphate) (BSDP) was synthesised and characterised, and its tribological behaviours as additives in polyurea grease and lithium complex grease were evaluated for steel/steel contact at 200 °C. The results indicated that BSDP could dramatically reduce the friction and wear of sliding pairs in the base grease of polyurea, and the tribological performances of BSDP in polyurea grease were significantly superior to the normally used molybdenum disulfide‐based additive package. Furthermore, BSDP in polyurea grease has better tribological behaviour than that in lithium complex grease at a constant load of 100 N. X‐ray photoelectron spectroscopy analysis indicated that boundary lubrication films composed of Fe(OH)O, Fe₂O₃, Fe₃O₄ and FePO₄ compounds containing the P–O bonds and nitride compounds were formed on the worn surface, which resulted in excellent friction reduction and antiwear performance. Copyright © 2016 John Wiley & Sons, Ltd.     

New Mixed Esters with a Complex Alkyl‐Aryl Structure Considered as Tribological Fluids

This paper presents the results of a study carried out to produce synthetic ester oils of mixed structure and based on phthalic anhydride with beneficial tribological properties. Three series of unsymmetric diesters were synthesised using aliphatic alcohols such as n‐propanol, n‐butanol, n‐hexanol, 2‐ethylhexanol, isodecanol, and isotridecanol, along with special alcohols of a complex alkyl‐aryl structure, namely 2‐phenoxyethanol, 2‐((o‐sec‐butyl)phenoxylethanol, and 2‐ftp‐nonyl)phenoxylethanol. Also synthesised were symmetric esters based on these special aliphatic‐aromatic alcohols. The variation in the principal properties as a function of both the length of the aliphatic chain introduced by the aliphatic alcohol and the length and position of the aliphatic pendant chain on the aromatic nucleus of the complex alkyl‐aryl alcohol was assessed. Based on this, it has been possible to obtain fluid products with variable properties. The introduction of the aromatic function in the structure of these diesters leads to interesting features, and the wide range of viscosity values demonstrates their versatility.