Synthesis and Study on Tribological Properties of Tri-n-butyl Phosphorotetrathioate

The chemical structure of O,O,O-tri-n-butyl phosphorothioate (TBSTP) and S,S,S-tri-n-butyl phosphorotetrathioate (TBTTP) synthesized in laboratory were analyzed by means of mass spectrometer(MS) and Bio-Red Win-IR spectrometer (FT-IR). The extreme-pressure, antiwear and friction-reducing properties of liquid paraffin with TBSTP and TBTTP as additives were examined with a four-ball machine. The worn surfaces of the steel ball were analyzed by means of X-ray photoelectron spectroscopy (XPS) and scanning electron micro-scopy (SEM). It has been found that the two compounds as additives in liquid paraffin are effective in improving the antiwear behavior and load-carrying capacity. But they can′t improve the friction-reducing behavior of liquid paraffin. The SEM morphologies and the XPS analytical results of the worn surfaces indicate that the additives absorbed in the surface by the physical or chemical process and tribochemical reactions were involved for steel-steel frictional pair, with the formation of a multiple boundary lubricating film composed of phosphorothioate and tribochemical reaction products of the lubricants.