Protic ammonium bio-based ionic liquid crystal lubricants

© 2021 Elsevier LtdBis(2-hydroxyethyl) ammonium stearate (DES) protic ionic liquid crystal (PILC) has been added in 1 wt% and 2 wt% proportion to di-bis(2-hydroxyethyl) ammonium succinate (DSU) protic ionic liquid (PIL) to obtain (DSU+1%DES) and (DSU+2%DES) lubricant blends. The new blends are non-Newtonian fluids with liquid crystalline domains. Addition of (DES) PILC to (DSU) PIL reduces running-in friction coefficient in more than 70% and prevents surface damage, decreasing wear rate in more than one order of magnitude. Optical profilometry, optical and scanning electron microscopy (SEM), energy dispersive (EDX) and X-ray photoelectron spectroscopy (XPS) have been used to analyze surfaces after the tribological tests.