Wear in multiple network elastomers arises from the continuous accumulation of molecular damage rather than microcrack growth

Tire wear releases millions of tons of particles annually, bearing immense industrial and environmental impact. However, efforts to mitigate the wear of elastomeric materials remain largely empirical, due to a limited understanding of the underlying damage mechanisms that cause wear. Employing mechanochemical approaches on model multiple network elastomers, we uncover how polymer strand scission events - the elemental damage units in these disordered networks - evolve during frictional wear. Our findings demonstrate that discrete micro-slippage at rough contacting asperities damages the material several micrometers below the surface through stress-activated bond scission events. This steady accumulation of subsurface damage ultimately leads to material erosion through the generation of a degraded viscous layer, painting a new picture of wear as a continuous damage growth process. Our approach further demonstrates an enhanced resilience to wear when tuning material architecture to reduce sensitivity to stress fluctuations, paving the way for knowledge-based strategies to develop more sustainable materials.