Tribology of Phenolic-based Composites

Abstract

Phenolic-based composites for automobile frictional materials contain a variety of inorganic fillers and modifiers in addition to the base resin and fibers (mostly asbestos). The frictional behavior at low speeds do not provide a sufficient foundation for the prediction of the friction and wear behavior at high speeds because the temperature rise at high speeds causes chemical changes in some of the friction constituents of the composite system.The purpose of this paper is to provide a clear interpretation of the frictional performance of the basic phenolic resins at high speeds. The thermal and mechanical properties of the phenolic resins may significantly affect the friction and wear behavior of the composites. Three types of phenolic resin which have different thermal stabilities have been tested. It has been shown that the frictional behavior at high speeds involves three changes in the frictional coefficient with sliding distance: an initial decrease at low speeds, an increase at medium speeds, and a final constant value after frictional changes with fluctuations. The frictional behavior closely corresponds to that of the temperature change during sliding. An increase in density of cross-linking reduces the wear rate. Insufficient cross-linking of the phenolic resin produces different frictional behavior compared with the fully cross-linked structure.