Rapid and simple synthesis of lignosulfonate-based hydrogel as green lubricating grease with enhanced tribological performance

With growing environmental concerns and resource depletion, developing green lubricants is essential. This study presents a lignosulfonate (LS)-based hydrogel grease, synthesized via a one-step, eco-friendly process at room temperature. Ammonium persulfate (APS) initiated polymerization and crosslinking, with ferric chloride (FeCl₃) as a secondary crosslinker. The 15 % LS hydrogel reduced the coefficient of friction (COF) by 37.5 % and wear volume by 31.25 % compared to the 0 % LS sample. A chemically adsorbed tribofilm, rich in oxygen and sulfur, formed on worn surfaces, enhancing lubrication and wear resistance. This study highlights LS hydrogels as promising green lubricants, offering improved tribological performance and environmental sustainability.