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Chemical, Physical and Tribological Investigation of Polymercaptanized Soybean Oil

Girma Biresaw, James C. Lansing, Grigor B. Bantchev, Rex E. Murray, Rogers E. Harry-O’Kuru
Tribol Lett 2017 v.65 no.3 (article 87) pp. 1-16
fluid mechanics, friction, lubricants, mixing, oxidative stability, solubility, soybean oil, sulfides, sunflower oil, thiols, viscosity
Polymercaptanized soybean oil (PMSO) was investigated for its chemical, physical and tribological properties relative to soybean oil (SO) and also as a potential multi-functional lubricant additive in high oleic sunflower oil (HOSuO). Analytical investigations showed that PMSO is obtained by conversion of 76% of double bonds in SO into thiol (-SH) and sulfide (R-S-R’) groups. PMSO product mixture comprised 70% monomer and 30% oligomers, versus 99.6 and 0.4%, respectively, for SO. Relative to SO, PMSO displayed higher density, viscosity and oxidation stability; similar cold flow properties; and lower viscosity index. PMSO displayed good solubility in HOSuO (>10% w/w), but poor solubility in polyalpha olefin-6 (<1% w/w). Investigation of PMSO as a lubricant additive in HOSuO showed that it had multi-functional properties. Thus, blending of PMSO in HOSuO resulted in improved oxidation stability; improved friction and wear in 4-ball anti-wear tests; improved extreme pressure (EP) properties in 4-ball EP tests; and no effect on cold flow properties.