Lignin and devulcanized tyre crumb for next-generation rubber composites

Abstract This study investigates the characterization and processing of rubber crumb (RC) obtained as a waste from tread part of truck tyres with a focus on its devulcanization and stabilization using kraft lignin. Thermogravimetric analysis was employed to assess the composition of RC, revealing a three-step degradation pattern. Soxhlet extraction demonstrated the influence of processing temperature on sol fraction and together with rheological testing indicated that mechanical shearing at 65 °C (RC65) maximizes polysulphidic chain scission. Fourier transform infrared spectroscopy (FTIR) confirmed changes in alkane and sulphur-related bands, supporting partial devulcanization of RC samples. FTIR analysis further revealed that lignin (RCL) reduces the main chain scission in devulcanized RC, suggesting a stabilizing effect during devulcanization. The incorporation of devulcanized RC samples in virgin SBR compound resulted in improved cross-linking behaviour and mechanical properties, particularly for SBR/RC65 and SBR/RCL samples. Scanning electron microscopy further confirmed good compatibility of RCL with the SBR matrix. These findings underline the potential of lignin-stabilized devulcanized rubber as a sustainable additive in new rubber composites, advancing waste tyre recycling technologies. Graphical abstract