Tribological properties of polymer composites containing barite (BaSO4) or potassium titanate (K2O • 6(TiO2))

Tribological properties of particulate barite (BaSO4) and potassium titanate (K2O.6(TiO2)) whiskers, the two major ingredients currently used for commercial brake friction materials, were investigated. A novolac resin was used as a binder for test specimens and a block-on-disk tribometer was used to assess friction characteristics of the two ingredients. Experimental results showed that the BaSO4-filled composite produced large frictional oscillations and created severe damage on the gray iron counter surface, while the composite filled with the same amount of K2O.6(TiO2) whiskers showed smooth sliding without large friction force fluctuation. The cause of the different frictional behavior was investigated by considering stick-slip and mechanical properties of the composites, which was largely based on the morphology of the two ingredients and their role in reinforcing the composite. The results from this comparative study suggest that the friction characteristics of commercial friction materials can be strongly affected by the two ingredients, which have been considered as minor constituents for brake performance.