Characterization of thermal-oxidative aging mechanism of commercial tires

•Thermo-oxidative aging is the main cause of chemical bond breaking in tires;•The belt thermal-oxidative aging mechanism of commercial tires was studied;•Test specimens were obtained from a bus that traveled the same fixed route;•Thermogravimetric analysis revealed that the compound remained thermally stable;•The oxygen and its diffusion caused thermal-oxidative aging of commercial tires. The lifespan of tires is associated with the stability of chemical bonds in natural rubber compounds, and thermo-oxidative aging is the main cause of chemical bond breaking in commercial tires. The aim of this study was to characterize the belt thermal-oxidative aging mechanism of commercial tires to understand the damage to their mechanical properties owing to tire aging. Therefore, the mechanical, physicochemical, and thermal properties of virgin and tires aged on the road at varying mileages (0, 5,000, 25,000, 50,000, 100,000, and 150,000 km) were studied. Three types of aging processes were observed. Aging type I occurs under anaerobic and aerobic conditions and at low temperatures, type II occurs only under anaerobic conditions at high temperatures, and type III occurs under aerobic conditions and at high temperatures. Samples from tires at all mileage levels showed high thermal stability with mass loss occurring at 288 °C (TMAX). It was concluded that the main mechanism responsible for thermal-oxidative aging in commercial tires is the presence of oxygen and its diffusion between the liner and belt packages. Aging is a natural and an irreversible process. Therefore, ensuring compound stability is one of the approaches used by the tire industry and rubber product manufacturers to minimize the repair costs for the consumer and guarantee vehicular safety and tire structural performance.