An Investigation on the Friction and Wear Properties of Perfluorooctane Sulfonate Ionic Liquids

The study aims to explore the physicochemical and tribological properties of perfluorooctane sulfonate ionic liquids (PSILs) C₈F₁₇SO₃N₄₄₄₄ and C₈F₁₇SO₃P₄₄₄₄. The results showed that C₈F₁₇SO₃P₄₄₄₄ exhibited excellent friction-reducing and anti-wear properties at both room and high temperatures, and C₈F₁₇SO₃N₄₄₄₄ presented excellent tribological properties at high temperature when they were used as lubricants for steel/steel, steel/copper, and steel/aluminum friction pairs. As compared with traditional fluorine-containing ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide (L-F104), increasing the fluorocarbon chain length of the anion is proven to be an effective way to improve the performance of the PSILs in terms of hydrophobicity, corrosion resistance, and tolerance to extreme pressure, thereby making them more suitable to be used as lubricants under harsh conditions. The X-ray photoelectron spectroscopy analysis indicated that physical adsorption and tribochemical reactions occurred and generated protective films on the sliding surface during the rubbing process, which reduced the friction and elevated the anti-wear efficiency of the PSILs.