The Effect of the Environment on the Friction and Wear of Blended Rubber

The friction and wear of rubber are properties that are affected by the environment, especially by the oxygen in the air. Natural rubber (NR) is most sensitive to air, butadiene rubber (BR) is scarcely affected by the presence of air, while styrene butadiene rubber (SBR) is intermediate compared to NR and BR. Both the abrasive and fatigue wear rates of NR and BR blends are known to decrease by increasing the BR content. To reduce the wear rates of NR vulcanizates in the air, SBR was blended with NR. In severe rubbing experiments against abrasive cloths, the wear rate of the NR-SBR blends slightly decreased by increasing the SBR content. The NR-SBR blends showed considerable reduction in wear under fatigue wear conditions against metal gauze. Similar experiments were also conducted for SBR-BR blends. Blending with BR showed a substantial reduction in wear, especially in fatigue wear. When NR-BR, NR-SBR, and SBR-BR blends were rubbed against metal gauze in vacuum, the friction and wear of these three blended rubbers was lower in vacuum than in room air. It is concluded that the wear resistance of the blended rubber is affected by its sensitivity to air as well as by the mechanochemical properties of the blends under fatigue wear conditions.