The influence of devulcanization and revulcanization on sulfur crosslink types: Recycling of ground tyre rubber by solid-state shear milling

This paper seeks to establish whether bond breaking from the S3M process has some selectivity between mono-/di-/poly- sulfidic bonds. The crosslink densities of ground tyre rubber (GTR) with increasing numbers of solid-state shear milling cycles (1-4) were established by swelling in toluene. The sulfur bond ratios of these GTRs was measured, following the process from Choi and Kim [https://doi.org/10.1016/j.polymertesting.2014.12.007]. This will allow both the S3M process itself and the revulcanization process to be modified to provide greater control of the properties of recycled rubber. GTR that had been through 4 S3M cycles was also blended with virgin natural rubber (vNR), and different sulfur/accelerator ratios were applied to reintroduce specific sulfur bond-types. Finally, the overall effect of crosslink densities and sulfur bond ratios of these recycled blends was evaluated by tensile testing.