Investigation of Changes in the Structure and Adhesion Properties of the Surface of Tread Tire Rubber during Friction

Different types of tread rubbers used in pneumatic tires of different applications are studied in the present work. The influence of various rubbers used in manufacturing treads on the rubber surface structure and its tribological, mechanical, and adhesive properties is estimated. A study and comparative analysis of the results of tribological tests and microscopic studies are performed. Microscopy of the sample surfaces is performed both before and after the tribological tests. To visualize the surface, the methods of scanning electron microscopy (combined with elemental analysis) and scanning probe microscopy are used. The character of changes occurring on the surface during friction, which is simulated on a tribometer with a rubber ring–disk contact circuit, is studied using these microscopy methods. It is established that the worn surfaces of all elastomers under study have a close structure and typical surface microrelief, but have different adhesion and mechanical properties depending on the type of rubber used in the rubber base and the used fillers. It is noted that high values of the sliding-friction coefficient and similarity of the rubber surface structures prove that their abrasive wear mechanisms are identical. The performed tribological laboratory tests show that the friction coefficient of the tread rubbers at high temperatures decreases with an increase in the normal load, while the opposite trend is observed at low temperatures. It is established that the change in the relaxation properties of rubbers due to temperature changes greatly affects the dependence of the friction coefficient on the sliding speed, while the energy loss due to friction is maximal in the temperature range of 15–20°C.