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Colloidal thiophosphorus calcium salt as antiwear additive
Author(s) -
Delfort Bruno,
Born Maurice,
Daoudal Bertrand,
Chivé Agnes
Publication year - 1996
Publication title -
lubrication science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.632
H-Index - 36
eISSN - 1557-6833
pISSN - 0954-0075
DOI - 10.1002/ls.3010080204
Subject(s) - calcium , colloid , chemistry , calcium hydroxide , inorganic chemistry , micelle , pulmonary surfactant , thermogravimetric analysis , dynamic light scattering , phosphate , salt (chemistry) , chemical engineering , nuclear chemistry , organic chemistry , nanoparticle , aqueous solution , biochemistry , engineering
This 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. The 31 P‐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 (thio)phosphate core.