Ashless and non-corrosive disulfide compounds as excellent extreme pressure additives in naphthenic oil

Medium chain chlorinated paraffin (MCCP) and zinc dialkyl dithiophosphate (ZDDP) are widely used as extreme pressure (EP) additives in metalworking fluids (MWFs). Currently, sulfur-based EP additives are found to be more environmentally friendly and biodegradable. Although naphthenic base oil (NBO) is suitable to be used in MWFs due to its low pour point and better emulsified ability, there is a lack of study on the sulfur additives in this type of oil. In this study, two organo disulfides compounds namely dibenzyl disulfide (DBDS) and dioctyl disulfide (DODS) have been synthesized as EP additives. These DBDS and DODS demonstrate an excellent EP performance, non-corrosive, ashless, and good anti-wear (AW) properties in NBO. The DBDS shows 1961 N (EP value) and 6 mm(2) (AW scar area) in NBO, which is superior to DODS, MCCP and ZDDP. This is due to the formation of sulfur-based tribofilm on the interface that acts as a protective sulfur layer thus, enhancing the property of EP. (C) 2022 Published by Elsevier B.V.

Automated summary

Two organo disulfides compounds, DBDS and DODS, have been synthesized and demonstrate excellent EP performance and anti-wear properties in naphthenic base oil, showing superior performance compared to traditional EP additives like MCCP and ZDDP. This is due to the formation of a protective sulfur-based tribofilm on the interface that enhances the EP property.