Effect of biotic and abiotic degradation on the surface and bulk of rubber compounds

Tyre and Road Wear Particles (TRWPs) represent a significant source of particulate and chemical pollution. While the degradation of conventional plastics is well-documented, the multi-component nature of cured rubber compounds remains poorly understood. This study establishes a systematic baseline for assessing the degradation of well-defined model rubber compounds. Two distinct formulations were investigated: a model tread compound (TC) containing S-cured Natural Rubber (NR), Styrene-Butadiene Rubber and silica filler, and a GUM compound composed solely of peroxide-cured NR. To ensure reproducibility and maximize environmental exposure, compounds were processed into thin films. Degradation was assessed through a multidisciplinary approach combining abiotic aging via accelerated UV photo-oxidation to simulate sunlight exposure and biotic degradation, using microbial communities enriched from soil potentially contaminated with TRWPs. Results from Scanning Electron Microscopy and FT-IR ATR revealed that combined photo-aged and microbial incubation most effectively induced surface-level alterations, such as microvoids and surface erosion. In GUM samples, bulk NR polymer degradation was mainly observed. Conversely, TC samples showed a stronger synergistic response, involving transformation of NR into a more thermally stable form. Derivative Thermogravimetry analysis of the TGA mass loss curves provided a semi-quantitative framework to monitor elastomers transformation. Overall, this research highlights a synergic effect between abiotic aging and microbial colonization in rubber degradation. These findings will help in developing guidelines for the environmental degradation of TRWPs and offer insights into the development of “Safe and Sustainable by Design” tyre formulations, contributing to the mitigation of the environmental impact of tyre materials in a lifecycle perspective.