Design, Synthesis, and Tribological Behavior of an Eco-Friendly Methylbenzotriazole-Amide Derivative

Recently, researchers have been committed to boosting the environmental friendliness and functional performance of multifunctional additives. In this study, an eco-friendly methylbenzotriazole-amide derivative (MeBz-2-C18) was designed and synthesized, with ethylamine serving as the linkage between methylbenzotriazole and the oleoyl chain. The structure of MeBz-2-C18 was characterized by nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Subsequently, the storage stability and tribological behavior of MeBz-2-C18 and the commercial benzotriazole oleamide salt (T406) were comparatively evaluated. The covalently-bonded MeBz-2-C18 exhibits superior thermal stability, along with boosted storage stability and tribological performance in the synthetic base oil. Specifically, 0.5 wt.% addition of MeBz-2-C18 and T406 can reduce the average wear scar diameter (ave. WSD) by 21.6% and 13.9%, respectively. To further explore the micro-mechanism, the electrostatic potential (ESP) and worn surfaces were analyzed with scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The results show that MeBz-2-C18 possesses stronger adsorption on the metal surface, and its amide bond preferentially breaks during friction. This reduces the interfacial shear force and promotes the film formation of iron oxides, thus resulting in superior tribological performance.