Highly effective ashless and non-corrosive dimercaptobenzothiadiazole as multifunctional lubricant additives in naphthenic base oil

Chiu Ling Ong; Yew Chong Lai; Thorsten Heidelberg; Wai Kit Tang; Vannajan Sanghiran Lee; Nader Ghaffari Khaligh; Joon Ching Juan

doi:10.1039/d3ra05692a

Highly effective ashless and non-corrosive dimercaptobenzothiadiazole as multifunctional lubricant additives in naphthenic base oil

RSC Adv. 2023 Oct 19;13(44):30733-30742. doi: 10.1039/d3ra05692a. eCollection 2023 Oct 18.

Authors

Chiu Ling Ong¹, Yew Chong Lai², Thorsten Heidelberg³, Wai Kit Tang³, Vannajan Sanghiran Lee⁴, Nader Ghaffari Khaligh¹, Joon Ching Juan^{1

5}

Affiliations

¹ Nanotechnology and Catalysis Research Centre, Level 3, Block A, Institute for Advanced Studies, University of Malaya 50603 Kuala Lumpur Malaysia jcjuan@um.edu.my.
² Oleon Port Klang Sdn. Bhd. 57, Jln Sungai Pinang 4/3, Taman Perindustrian Pulau Indah 42920 Pelabuhan Klang Selangor Malaysia.
³ Department of Chemistry, Faculty of Science, University of Malaya 50603 Kuala Lumpur Malaysia.
⁴ Department of Chemistry, Centre of Theoretical and Computational Physics (CTCP), Faculty of Science, University of Malaya 50603 Kuala Lumpur Malaysia.
⁵ Faculty of Engineering, Technology and Built Environment, UCSI University Cheras 56000 Kuala Lumpur Malaysia.

Abstract

The conventional medium chain chlorinated paraffin (MCCP) and zinc dialkyl dithiophosphate (ZDDP) additives have greatly enhanced the extreme pressure (EP) and anti-wear (AW) performance of the metalworking fluids. However, chlorine- and zinc-containing additives are restricted in use due to eco-toxicity issue. Herein, ashless and non-corrosive dimercaptobenzothiadiazole derivatives, namely bis-2,5-benzylsulfanyl-[1,3,4]thiadiazole (BBST) and bis-2,5-octylsulfanyl-[1,3,4]thiadiazole (BOST) consist of three sulfur atoms have been synthesized and evaluated. The performance of BBST shows a weld load (P_D) of 3089 N and AW value of 5 mm², which represents an improvement of 3.1 and 7.4 folds over naphthenic base oil (NBO). In addition, BBST also outperformed BOST, MCCP, and ZDDP in terms of its weld load and AW properties. Based on XPS analysis and molecular electrostatic potential maps (MEPS), BBST exhibits superior tribology performance due to the interaction between the sulfur (S), nitrogen (N), and π-electrons of the benzene ring with the metal surface. The formation of FeS, Fe₂O₃ and Fe⋯N coordinate bonds contributes to the creation of an excellent tribofilm.