Document OVV6a9bo6JDv3BQkz0Q0zYJj

S NON-ASBESTOS FRICTION MATERIALS by ' * Michael G. Jacko, Ph.D. Bendix Advanced Technology Center Southfield, Michigan and Mr. Charles M. Brunhofer and Mr. F. William Aldrich* Bendix Friction Materials Division Troy, New York ABSTRACT Friction materials for automotive orakes are complex composites containing three general types of ingredient materials: reinforcing fibers; modifiers that adjust or maintain friction level, wear- rate, and noise properties; and organic resin binders. Historically, the foundation or major constltutent of automo tive friction materials has been asbestos fiber, so chosen because of thermal stability, friction level, reinforcing properties, availability, and relatively low cost. Numerous substitutes for asbestos in conventional organic materials have been evaluated, including both naturally occurring and synthetic materials. Direct substitution of these alternative materials in conventional formulations has resulted in poor friction levels, friction instability, roughness, structural failure, increased noise, mating surface deterioration and/or front-to-rear vehicle brake Imbalance. Complete reformulation, not simple substitution, is necessary to meet the numerous, complex performance requirements of consumers, manufacturers, and government standards, such as FMVSS 105-75 and FMVSS 121. In the 1960's, a new class of friction materials, called semlmetallies, was developed to meet severe braking requirements, primarily In heavy-duty disc brake and extreme duty truck block applications. Semlmetalllcs operate satis factorily against the ventilated cast-iron rotors in the smaller brakes of downsized cars, as well as against the solid rotors found in the lighter brakes of new front wheel drive vehicles. Semlmetalllcs rely on steel fiber and pow der metallurgy techniques for reinforcement, and do not require asbestos. The Improved performance of semlmetalllcs compensates for their higher costs due to more expensive ingredients, higher specific gravity, and more costly pro cessing requirements. Overall development took more than 10 years from intro duction to significant customer acceptance. Presented by Mr. Charles M. Brunhofer 9