Phosphonates of vegetable oils – Characterization as lubricants

Authors: Biresaw, Girma; Bantchev, Grigor; Harry O Kuru, Rogers

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2020
Publication Date: 11/30/2020
Citation: Biresaw, G., Bantchev, G.B., Harry-O'kuru, R.E. 2020. Phosphonates of vegetable oils – Characterization as lubricants. Journal of the American Oil Chemists' Society. 98(1):89-102. https://doi.org/10.1002/aocs.12448.
DOI: https://doi.org/10.1002/aocs.12448

Interpretive Summary: Modern lubricants are complex mixtures of base oils with a multitude of additives, each with its own specific function. Successful formulation of biobased lubricants requires using biobased base oils and biobased additives in order to get all the expected lubrication, environmental, health, and economic benefits. ARS scientists in Peoria, Illinois, synthesized new anti-wear additives by adding phosphorus on soybean and high oleic sunflower oils to make phosphates. The addition of phosphorus is known to form anti-wear films during lubrication and minimizes the wear of friction surfaces. Lubricant blends with these new phosphonate additives were tested for their friction and wear properties on a four-ball tribometer. The results showed that the biobased phosphonates additives had similar or better friction properties than petroleum based commercial phosphate additives. The commercial phosphate additives are widely applied in motor oil, hydraulic, gear oil, metalworking and many other lubricant formulations. Successful commercialization of phosphonates of soy and other vegetable oils will create new demand for seed oil crops and lead to improvements in the income of farmers and the rural economy.

Technical Abstract: Dialkyl phosphonates of vegetable oils were synthesized by reacting soybean (Soy) and high oleic sunflower (HOSuO) oils with dialkyl phosphites. Dimethyl, diethyl, and di-n-butyl phosphites were used in the synthesis and the resulting phosphonates were obtained in good yield and thoroughly characterized. All six phosphonates displayed poor solubility in polyalphaolefin-6; and four displayed adequate solubility (> 20% w/w) in HOSuO. Evaluation as anti-wear (AW) additives in HOSuO base oil blends showed the biobased phosphonates have similar coefficient of friction and similar or better wear scar diameter than zinc dialkyl dithio phosphates (ZDDP). It is concluded that vegetable oil phosphonates provide a promising biobased alternative to ZDDP and other commercial petroleum-based AW additives currently used in lubricant formulations.