Ice-rubber friction mechanisms across scales

Rubber-ice friction is governed by the coupled contributions of viscoelastic adhesion and interfacial heating. This work provides unique in situ/in operando insight into the friction mechanisms from the macroscopic to the molecular scale using combined experimental measurements and analytical modelling approaches. Simultaneous force and real contact area imaging were used to quantify the real shear stress of SBR-silica elastomers spanning a small-strain, low-frequency shear-modulus range of 1-8 MPa (a low glass transition temperature of ∼-60 °C) during pure sliding over 50 µm s^-1-1 m s^-1 and at environmental temperatures down to -30 °C. The normalized real contact area exhibited a non-monotonic velocity dependence; together with a bell-shaped shear stress-velocity curve, this revealed three friction regimes: at low velocity, adhesion and viscoelastic dissipation dominated thermal effects; near the peak, frictional heat generation increased; and at high velocity, thermally driven mechanisms, including advection-dominated heat removal, became more significant, with the possible occurrence of localized interfacial melting. No bulk melting was observed. The novelty of this work relies on bridging the scales in ice-rubber friction mechanisms. At the macroscopic scale, a simple thermal analysis of the rubber-ice sliding interface yielded a dimensionless average contact temperature that collapsed across all compounds and test conditions considered. At the molecular scale, Chernyak-Leonov kinetics was used to describe elastomer chain attachment-detachment on ice and its temperature dependence. Successfully confronting our experimental results with this multiscale model led to a predictive interfacial shear stress model that, when supplied with the measured real contact area, reproduced both the magnitude and shape of the friction response.