Sustainable Kilogram-Scale Conversion of Tire Pyrolysis Waste into Nanosized Onion-like Carbons with Extraordinary Lubricant-Additive Properties

Tire pyrolysis waste (TPW) is converted into highly crystalline and nanosized onion-like carbons (OLCs) on a kilogram scale using an easy and controlled heat treatment. An OLC-dispersed additive-free group-II N500 base oil (BO) sample exhibited increased density, lower viscosity, and reduced internal fluid shear stress compared to BO. The nanoscale of OLC induced a change in the dispersing medium's conformation and free volume, resulting in a non-Einstein-like decrease of viscosity. When used as a lubricant in the four-ball wear test, the OLC-added BO sample caused nanoscale sliding and rolling effects at the points of contact, considerably reducing the coefficient of friction and wear. Surprisingly, TPW also showed similar behavior to OLC. Here, it is elucidated that OLC and TPW are anti-friction and anti-wear nanoadditives in lubricants that reduce friction and wear substantially. TPW could also be used as a low-cost additive in lubricants with no stringent restrictions on the presence of minor impurities and in several other applications. This is expected to ease the economics involved and facilitate the liberal use of OLC in various applications, as discussed in brief in this work.