Influence of Chemical Structures in Sulfurized Fats on Antiwear Behavior

Sulfurized methyl 10-undecenoate was used as the substance typifying sulfurized fatty extreme-pressure lubricant additives. The characteristic chemical structures in sulfurized methyl un-decenoate are sulfur-bridged long-chain di-esters, of which 1,20-dicarbomelhoxy-9,12-dimethyl-10,11 -dithiaeicosane is an example. The antiwear performance of this dithio-ester with respect to hardened AISI1095 steel in a pin-and-disk apparatus was indistinguishable from that of sulfurized methyl undecenoate. Esters such as methyl laurate and 1,18-dicarbomethoxyocta-decane did not show the antiwear behavior typical of sulfurized methyl undecenoate. Organic sulfides—-di-n-octyl monosulfide, di-n-octyl disulfide, di-n-octyl tetrasulfide, di-sec-octyl disulfide, d-t-octyl disulfide—behaved much differently than sulfurized methyl undecenoate. A mixture of methyl laurate and di-sec-octyl disulfide showed the same kind of antiwear behavior as sulfurized methyl undecenoate.