The tribological study of novel phosphorous–nitrogen type phosphoramidate additives in rapeseed oil

Abstract

Two novel phosphorous–nitrogen type phosphoramidate derivatives, dibutyl octadecylphosphoramidate and dimethyl 4-dodecylphenylphosphoramidate, were synthesized and applied as lubricant additives in rapeseed oil. Using a four-ball machine and standard method, the tribological behaviors of these additives in rapeseed oil were compared with commercial lubricant additives dodecan-1-aminium butyl 7-methyloctyl phosphate (coded T308B) and dibutyl phosphonate (coded T304). The results show that the phosphoramidate derivatives possess excellent antiwear, friction-reducing properties and good extreme pressure capacities. The tribological mechanism was investigated by X-ray absorption near edge structure spectroscopy. It is proposed that the prepared compounds as additives in rapeseed oil form a protective film on the rubbed surface, and the film contains phosphate and/or polyphosphate which can affect the tribological behavior.