Revisiting the correlations between wet skid resistance and viscoelasticity of rubber composites via comparing carbon black and silica fillers

The present article revisits the role of viscoelasticity in wet skid resistance (WSR) of rubber composites by comparing the effects of carbon black (CB) and silica on WSR. WSR was determined with a British Pendulum Skid Tester on a wet ground glass surface. Under shear and tensile modes, tanδ of the composites was measured at 0 °C and 10 Hz over a wide range of strain (0.7%-10%) via a dynamic mechanical analyzer. For CB-filled composites with nearly the same hardness, a high correlation coefficient (R² = 0.98) between WSR and tanδ under both shear (0.7%-10%) and tensile (4%-7%) modes was obtained. Tanδ at tensile strain of 4% was thus adopted as a parameter to characterize viscoelasticity. For rubber composites with rough surface, WSR and tanδ showed a high correlation in styrene butadiene rubber (SBR) composites individually filled with CB and silica, while for rubber composites with smooth surface, a high correlation was also observed but did not depend on the type of filler. Silica-filled SBR composites showed higher WSR, when compared with those filled with CB, mainly due to the higher nanohardness of silica. All the above results demonstrate that WSR can be predicted from viscoelasticity for composites with similar surface roughness and micro-hardness.