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Abstract
Diisopropylphosphite reacts with sulphur and ammonia to form ammonia monothiophosphoric acid-diisopropylester which, by subsequent reaction with different monochloroacetic acid esters, yields the corresponding monothiophosphoric-acid-O,O-diisopropyl-S-carboalkoximethylesters. These compounds show different wear- and friction-reducing properties in lubricating oils. The tribochemical activity at higher temperatures increases with the chain length of the carboxylic ester group. Auger electron spectroscopy (AES) of the worn metal surface shows that the wear reducing properties correspond with the phosphorus content in the metal surface produced by tribofragmentation of the monothiophosphates. A possible explanation of this effect is discussed.