The influence of carbon nanotubes on the abrasion and crack growth behaviors of styrene–butadiene rubber compounds

In this study, the influence of carbon nanotubes (CNTs) on the wear and crack growth behaviors of styrene–butadiene rubber (SBR) vulcanizates was reported. Two types of carbon black (CB)-filled SBR compounds were prepared with a total filler loading of 50 phr. In each case, a small fraction (∼3 phr) of CB was replaced either with pristine CNTs (p-CNTs) or with surface-modified CNTs (T-CNTs). The surface modification of CNTs was carried out using a silane coupling agent (Si-69). Wear resistance and crack growth behaviors were evaluated by using a blade-type abrader and a dynamic fatigue instrument, respectively. The SBR-containing p-CNT exhibited reduced wear resistance, as the unmodified CNT was more easily pulled out by the blade during abrasion. On the other hand, the SBR containing T-CNTs demonstrated improved wear resistance (1 phr of T-CNT: 6–7.5% improvement), attributed to the enhanced interaction between the CNTs and the SBR matrix facilitated by the silane coupling agent, which reduced the amount of CNT pull-out. Crack growth resistance was improved in both SBR containing p-CNTs (7.1–60.6% improvement) and T-CNTs (39.8–71.8% improvement). This enhancement is explained by the gradual and partial pull-out of CNTs under repeated straining, which contributed to energy dissipation and improved fatigue resistance, even in the absence of surface modification.