The influence of devulcanization and revulcanization on sulfur crosslink types: Recycling of ground tyre rubber

Devulcanized rubber could be a valuable material feedstock to help manufacture sustainable rubber products. However, the differences in chemistry and structure of devulcanized rubber have limited industrial uptake. This work demonstrates how devulcanization affects the concentration and ratios of mono-, di- and poly- sulfidic crosslinks. These residual crosslinks make devulcanized rubber chemically dissimilar from virgin rubber, affecting (re)vulcanization. The hypothesis that sulfur rank of revulcanized material can be modified by sulfur/accelerator ratio was evaluated by two different cure packages. Despite substantial differences in accelerator/sulfur ratio, both recycled rubber compounds favoured formation of poly-sulfidic crosslinks.