Synthesis, hydrolytic stability and tribological properties of novel borate esters containing nitrogen as lubricant additives

Novel borate esters have been synthesized as friction-reducing and anti-wear lubricant additives by using boric acid, schiff base and long chain alkyl alcohol. Because a stable six-member ring of B with N coordination has been formed in the molecule of borate ester, it exhibits higher hydrolytic stability. Its friction-reducing and anti-wear properties were measured with a ball-on-disk and four-ball friction and wear tester. These experiments indicated that the friction coefficient is decreased by about 20-30% compared with that of base oil and the wear is also diminished. Furthermore, the performance is better than zinc dialkyldithiophosphorate (ZDDP) in certain conditions. Structural analysis of the rubbed surface by X-ray photoelectron spectroscope (XPS) and Auger electron spectroscope (AES) indicated that there were mainly adsorbed borate esters and B2O3 on the surface. Moreover, boron nitride was also detected. The boron element permeated strongly into the frictional surface. (C) 1998 Published by Elsevier Science S.A. All rights reserved.