Biocompatible\nand Biodegradable Emulsion Gel Lubricants

Due to inclusion\nof toxic and nondegradable base oils and additives,\nmost of the commercially available semisolid lubricants easily cause\nsevere environmental burdens and health risks. This therefore leads\nto the use of these lubricant products contrary to the principles\nof sustainable chemistry and engineering. To solve this crucial issue,\nin this work, we create a new type of eco-friendly emulsion-based\ngel lubricant that is able to combine the characteristics of traditional\ngel lubricants and oil-in-water emulsions. The advantages of employing\nthe emulsion gel lubricants include (1) facile preparation using lost-cost,\ncommercially available pentaerythritol oleate, chitosan, and water\nin the compositions; (2) high colloidal stability against droplet\ncoalescence and phase separation; (3) good anticreeping and thixotropic\nperformances that allow effective semisolid lubrication; and (4) excellent\nbiocompatibility and biodegradability that can strongly reduce their\npotential adverse health and environment impacts. It was found that\nthe emulsion gels can provide favorable friction and wear reductions\nfor hard steel surfaces even under very high load-bearing conditions\nowing to the formation of high-strength mixed lubrication films. Our\nstudy may provide new insights into design and production of functional\ngreen semisolid materials for engineering applications.