Carbon nanodots as an eco-friendly activator of sulphur vulcanization in diene-rubber composites

It is widely accepted that zinc oxide (ZnO) is the best activator for sulphur vulcanization of rubber composites. However, ZnO is recognized as a toxic substance for both human and aquatic organisms. Therefore, it is of great importance, but still challengeable to exploit eco-friendly alternatives to reduce ZnO, without comprising the performance of rubber composites. Herein, we describe a novel strategy to achieve substantial reduction of ZnO in diene-rubber composites, by utilizing carbon nanodots (CDs) as an efficient activator for sulphur vulcanization. With the substitution of CDs for ZnO, the cross-linking rate of the rubber composites remarkably accelerated, mainly due to the fact that the N-related moieties of CDs can facilitate the formation of sulphur-based networks via significantly reducing the activation energy of the cross-linking reactions. Moreover, the activation efficiency of the synthesized CDs was also confirmed in the rubber formulations filled with conventional fillers. We envisage that this strategy can provide a green and practical avenue towards the substantial pollution abatement from ZnO in rubber composites.