Horst Zinke

Synthesis and tribochemical behaviour of some monothiophosphoric acid derivatives

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.

Synthesis and Tribofragmentation of Monothio-Phosphates

Abstract Besides the well-known zinc dithiophosphates (ZDTP) phosphorus and sulfur containing ashless additives are used to improve the lubrication properties of modern engine and hydraulic oils. It is generally accepted that a wear reducing reaction layer is formed by additive tribofragmen-tation reactions in the friction zone of the metal surface. The composition of those reaction layers and the formation mechanism relative to the used additive is quite unknown. By systematic modification of monothiophosphates the influence of molecule parameters on the wear reducing properties were investigated (1).