Wear behavior of silica filled tire tread compounds by various rock surfaces

Wear of silica filled tire tread compounds made from natural rubber (NR) and styrene butadiene rubber (SBR) against various rock surfaces at different normal loads and frictional work was investigated. The rocks chosen, i.e. granite, quartzite, limestone and shale, had variation in hardness and chemical composition. Wear, V, increased with normal load, N and frictional work, F-w, and these were related by V = beta N-alpha and V = k F-w(n), where beta,alpha,k and n were constants and dependent on the nature of the abraded surface and the rubber. The rate of wear of SBR was found to be much lower than that of NR against all rock surfaces. All the results could be explained with the help of dynamic co-efficient of friction, frictional work and structural changes during abrasion. The rate of wear as well as the dynamic coefficient of friction decreased with silica filler loading up to certain loading and then increased. These were 60 phr silica for NR and 70 phr silica for SBR. The surfaces of NR and SBR when abraded against different rock surfaces became tarry on prolonged abrasion. The debris were oily and aggregated for NR compound and were particulate for SBR compound. The debris and the ridges were analyzed by an image processing technique.