Fig. 2: Vulcanization of linear polydienes and material composition of a tire.
From: From waste rubber to value polybutadiene modification for circular materials
a According to Morrison and Porter11, vulcanization proceeds via the following steps: (1) formation of an active accelerator complex through the interaction of zinc oxide (ZnO), the co-activator stearic acid (StH), and the accelerator N-Cyclohexyl-2-benzothiazole sulfenamide (CBS); (2) reaction of the aforementioned complex with sulfur to generate an active sulfurating species; (3) yielding cross-link intermediates through the interaction between the sulfurating agent and linear butadiene rubber. (4) formation of polysulfide cross-links, which gradually transform into shorter, more stable sulfur bridges. b Material composition of tires, consisting of vulcanized rubber and diverse additives (such as rayon and nylon cords, zinc oxide, carbon black, and sulfur amongst others).
