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

Tirepyrolysis waste (TPW) is converted into highly crystallineand nanosized onion-like carbons (OLCs) on a kilogram scale usingan easy and controlled heat treatment. An OLC-dispersed additive-freegroup-II N500 base oil (BO) sample exhibited increased density, lowerviscosity, and reduced internal fluid shear stress compared to BO.The nanoscale of OLC induced a change in the dispersing medium'sconformation and free volume, resulting in a non-Einstein-like decreaseof viscosity. When used as a lubricant in the four-ball wear test,the OLC-added BO sample caused nanoscale sliding and rolling effectsat the points of contact, considerably reducing the coefficient offriction and wear. Surprisingly, TPW also showed similar behaviorto OLC. Here, it is elucidated that OLC and TPW are anti-frictionand anti-wear nanoadditives in lubricants that reduce friction andwear substantially. TPW could also be used as a low-cost additivein lubricants with no stringent restrictions on the presence of minorimpurities and in several other applications. This is expected toease the economics involved and facilitate the liberal use of OLCin various applications, as discussed in brief in this work. This work demonstrates sustainable engineeringto reducethe reliance on non-renewable resources and to minimize environmentalpollution associated with lubrication.