Pre‐Adsorption Assisted Devulcanization of Scrap Tire Rubber

ABSTRACT

Waste tire rubber is one of the most challenging polymer materials to recycle because its sulfur crosslinks—established during vulcanization—render the material resistant to melting and impervious to dissolution in common solvents. Traditional devulcanization approaches rely on thermally driven mechanochemical action to rupture these crosslinks but often demand prolonged processing durations and substantial energy input while risking unintended degradation of the rubber's primary polymer backbone. This study introduces a solvent‐assisted devulcanization strategy in which scrap tire rubber is pre‐soaked in a solvent containing tetramethylthiuram disulfide (TMTD), a chemical devulcanizing agent, before thermo‐mechanical processing on an open mill. Pre‐soaking allows TMTD to diffuse into the swollen rubber matrix ahead of milling, initiating crosslink disruption under comparatively mild conditions. During processing, the pre‐diffused TMTD undergoes homolytic cleavage and neutralizes the reactive polymer radicals generated during sulfur bond rupture, enabling targeted crosslink dissolution while preserving the integrity of the primary polymer backbone. Compared to conventional batches requiring 57–60 min and over 63 × 10 ⁶  J of energy, the solvent‐pretreated batch (SFT) achieved effective devulcanization in just 21.5 min with an energy consumption of 24.04 × 10 ⁶  J and a specific energy consumption (SEC) of 4 × 10 ⁵  J/g. The devulcanized rubber from the SFT batch exhibited a tensile strength of 8.31 ± 0.44 MPa, elongation at break of 176% ± 8.45%, and toughness of 6.6 ± 0.64 MJ/m ³ . These findings were validated through FTIR, swelling, rheological, SEM, thermal, and mechanical analyses. This work establishes solvent‐assisted TMTD pre‐diffusion as an industrially viable and energy‐conscious processing strategy for recovering high‐performance recycled rubber with diminished processing severity and reduced energy demand.