Chemical Changes at Brake Wear Surfaces

During a fundamental investigation aimed at the further improvement of organic disc brake linings, chemical studies were made of brake wear surfaces. Electron microprobe and infrared analysis were used to study the layer which forms on the lining and the film which forms on the drum when a new lining is broken in. Both the lining surface layer and the drum film are discontinuous and contain thermally decomposed asbestos. Calcined asbestos as an added ingredient in experimental linings resulted in markedly improved frictional performance.