Thermal Stability and Fade Characteristics of Friction Materials

Automotive brake linings are complex composites of organic resin binders, asbestos fiber reinforcement, and property modifiers. Brake lining fade is believed to be due in part to gas evolution from pyrolysis of these components at the lining-drum interface. Differential thermal analysis, thermogravimetric analysis, and X -ray diffraction have been applied to the study of pyrolysis of these typical ingredients and the composites (linings) made from them. The relation between thermal decomposition of the lining components, the linings themselves, and fade in drag dynamometry is discussed. The final performance evaluation of friction materials with respect to fade characteristics can only be obtained from extensive qualification tests carried out on vehicles, one reason being that the true temperatures of the linings at their sliding interfaces with the drum are not known.