Alkyl-Ethylene Amines as Effective Organic Friction Modifiers for the Boundary Lubrication Regime

Abstract

With the pursuit of fuel economy in the automotive industry, recently low-viscosity lubricant technology has been widely improved. The present work has systematically discussed a series of sulfur- and phosphorus-free organic friction modifiers (FMs)alkyl-ethylene aminesby alkyl substitution from ethylene amines with various nitrogen-atom numbers and molecular configurations. Herein, the pin-on-flat reciprocation friction tests have exhibited that the addition of the novel alkyl-ethylene amines into base oil led to significant reductions in the friction coefficient (up to 23%). Further investigations of tribological properties at elevated temperatures demonstrated that the increased number of nitrogen atoms and the regular linear atomic arrangement contributed to an improvement of friction reduction (up to 66%) compared to the neat base oil. Notably, results of water contact angle measurement and infrared spectroscopy (IR) have provided favorable evidence that the novel FMs have adsorbed on the metal surface leading to the formation of a tribofilm, whereby the tribofilm prevented the sliding surfaces from direct asperity contact and markedly improved the tribological performance, as seen from the composition analysis of the worn surfaces by an energy-dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), and confocal Raman spectroscopy. Therefore, the present work can provide a practical reference for molecular structure design through investigation of structure–performance relations of lubricant additives.

Tribological Properties and Lubrication Mechanism of Nickel Nanoparticles as an Additive in Lithium Grease

“…The SEM images in Figure 4c-d The ability to adsorb onto a metal surface is essential to the effectiveness of additives. The contact angle measurements were performed to evaluate the adsorption behavior of nanometer Ni on the metal surface [22]. As shown in Figure 3e, after immersion in the base oil containing nanometer Ni, the contact angle between the steel plate and base oil decreased significantly, indicating that effective adsorption of the nanometer Ni on the metal surface can promote the rapid diffusion of oil on the metal surface and the formation of adsorption film.…”

“…Then the equal amount of PAO4 was dropped on the plate. The contact angle between the base oil and the metal plate was observed and recorded automatically [22]. Meanwhile, the change of contact angle with time was recorded.…”

Applications of sum-frequency generation vibrational spectroscopy in friction interface

“…The addition of certain compounds to the base oil can effectively reduce friction and wear. These compounds are known as friction modifiers [70,71]. The reduction in friction and wear is attributable to two aspects at the molecular level: the interaction between the base oil and friction modifier molecules, and the interaction between different modifier molecules.…”

Impact of Ionic Liquid Additives and Inorganic Fullerene-Like Tungsten Disulfide on Friction and Wear under Aqueous Environments

“…Ionic liquids provide an environmentally friendly alternative and have good thermal stability . The electrostatic behavior of ionic liquid additives aids in the physical tribolayer formation, effectively reducing friction. ,, In a study with oil and an alkylethylene amine additive, the long-chain molecules had formed ordered layered structures on the tribopair surfaces, which are gradually sheared away . Additionally, ionic liquids include nitrogen, phosphorus, and sulfur elements that are known as active elements, which reduce friction and wear due to the tendency to interact with steel .…”

“…13,15,16 In a study with oil and an alkylethylene amine additive, the long-chain molecules had formed ordered layered structures on the tribopair surfaces, which are gradually sheared away. 17 Additionally, ionic liquids include nitrogen, phosphorus, and sulfur elements that are known as active elements, which reduce friction and wear due to the tendency to interact with steel. 18 molecules including glycols, alkylamines, alkanolamines, and hydroxyls can be incorporated into ionic liquids that can form homogeneous mixtures in water to provide antiwear, anticorrosion, and antifoaming media.…”