摘要:

AbstractThe 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 bri

ISSN:0954-0075    

DOI:10.1002/ls.3010080202

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThis 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 calc

ISSN:0954-0075    

DOI:10.1002/ls.3010080203

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper describes the synthesis of an oil‐soluble colloidal calcium thiophosphate by a direct route. It consists of the reaction of calcium oxide or hydroxide with tetraphosphorus decasulphide and water in the presence of a surfactant such as a calcium alkylaryl sulphonate in an organic medium. Reaction and micellisation occurred simultaneously according to a one‐step process. The product is characterised by a high calcium, phosphorus and sulphur content. The colloidal nature of the product has been confirmed by dialysis. The31P‐NMR spectrum showed signals characteristic of a blend of different calcium thiophosphates, plus calcium phosphate. The product could be defined as a core of different calcium (thio)phosphates surrounded by a calcium alkylaryl sulphonate shell, according to a reverse micelle type association in oil. This compound was evaluated as an antiwear additive in a 130 Neutral Solvent mineral oil by anti‐wear and extreme‐pressure four‐ball tests. The extreme‐pressure characteristics depend on the concentration of mineral colloidal core in oil. The antiwear properties are a function not only of the concentration, but also of the colloidal core/surfactant shell ratio. Thermogravimetric analysis of these colloidal species shows a weight loss in the 350°C to 450°C range, due to surfactant degradation. The further evolution of weight loss up to 900°C demonstrates the high thermal stability of the colloidal calcium (thi

ISSN:0954-0075    

DOI:10.1002/ls.3010080204

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe 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 environmen

ISSN:0954-0075    

DOI:10.1002/ls.3010080205

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractMixed polymers have been concentrated to produce highly concentrated VI improvers based on polyalkyl methacrylates (PAMA) and olefin copolymers (OCP). Because of their liquid form and special viscosity/temperature relationship, these concentrates can be stored, shipped and processed at comparatively low temperatures. This, in combination with a high specific activity, favours the economic manufacture of multigrade oils.In the VW elastomer compatibility test, the new dispersant mixed polymers (d‐MP2) show absolutely neutral behaviour towards fluoroelastomers. In gasoline as well as in diesel engines they contribute noticeably to the dispersant potential, thus making it easier to comply with the requirements for API SH. Moreover, bench and road tests have revealed a major reduction of engine wear. The effect of different dispersant groups is compared by way of a simple laboratory test and an attempt is made at corroborating a hypothesis on wear reductio

ISSN:0954-0075    

DOI:10.1002/ls.3010080206

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effect of an electric field applied between rubbing surfaces on friction and wear characteristics was examined using a ballon‐disc testing apparatus under different lubrication conditions. The lubrication conditions were changed by changing the viscosity of the lubricants. By applying an electric field between the rubbing surfaces, the oxidation of the rubbing surface at the anode side is enhanced, and suppressed on the cathode side surface. The oxide film formed on the anode surface being harder than the bulk steel, the rubbing surface at the anode side was little worn, but that at the cathode side was abrasively worn. This wear characteristic could be utilised to attain favourable running‐in. The application of an electric field, however, is considered to promote the breakdown of any EHL film formed. Therefore the effect of the application of an electric field between rubbing surfaces is influenced by the lubrication condition that is being tes

ISSN:0954-0075    

DOI:10.1002/ls.3010080207

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY

ISSN:0954-0075    

DOI:10.1002/ls.3010080201

出版商:John Wiley&Sons, Ltd    

年代:1996

数据来源: WILEY