Federal-Mogul Corporation has developed a range of zero-copper and low-copper brake pad formulations using a new tribological fingerprinting process. These newly formulated brake pads will be sold under the Eco-Friction name.
As companies work to introduce alternative materials ahead of legal deadlines, Federal-Mogul’s Eco-Friction is now achieving excellent results in customer trials.
Copper is a key ingredient in high performance brake pad formulations, limiting pad and rotor wear, noise and judder and contributing to friction stability over a wide range of operating temperatures. The metal makes up 5 to 20 percent of the friction material mass in typical Non-Asbestos Organic (NAO) and Low-Steel formulations used in North America, Asia and Europe.
The presence of copper in brake pads, however, will be regulated and may eventually be eliminated due to concerns regarding its environmental impact.
“Federal-Mogul has succeeded in formulating low- and zero-copper Low-Steel and NAO brake materials for our Eco-Friction range that provide outstanding braking performance and confidence using tribological fingerprinting,” says Ramzi Hermiz, Federal-Mogul’s senior vice president, Vehicle Safety and Protection. “This process has given us deeper insight into the complex chemical characteristics and relationships within a brake pad’s friction material and has reduced the time required to identify optimum solutions. The approach means we have the tools to eliminate copper more efficiently and to deliver custom solutions more quickly.”
Considering the principles of friction, lubrication and wear, Federal-Mogul’s tribological fingerprinting process develops datasets for each of the raw materials that make up a brake pad. The company’s scientists then used knowledge of copper’s tribological fingerprint, and how its function changes as the brake pad heats and cools, to screen 1,500 raw materials and identify alternative materials with the same wear and friction pattern across the same temperature range.
“Developing these comprehensive datasets has enabled Federal-Mogul to create higher-performance brake materials with shorter development times,” explains Frank Münchow, director of technology and innovation, Vehicle Safety and Protection, Federal-Mogul. “Standard brake pad product development requires several iterations. The most time-consuming elements are the definition of the formulation’s main structure for wear rate and friction level. Our in-depth understanding of each material’s chemical and physical characteristics in combination with its tribological function removes the trial and error from brake pad development and makes us a better development partner. We are now able to replace a material with very high functionality, such as copper, in considerably less time than competitors, and we can validate an alternative material up to 50% faster depending on the material,” adds Münchow.
There is no single material that can replace copper. Brake pads are a formulation of 20 to 30 different materials, each with different functions. Federal-Mogul’s Eco-Friction range uses a variety of metal sulphides, minerals, abrasives, fibers, ceramic particles and types of graphite to achieve the same wear and friction characteristics as brake pads containing copper.
Legislation in certain states of the U.S. requires the phase-out of copper from brake pads, initially limiting copper content to less than 5% of total pad weight and eventually requiring levels of less than 0.5%. Vehicle makers are now specifying brake systems with the regulated levels of copper, making an alternative formulation the standard for future vehicles in many markets. Federal-Mogul has already secured new customer contracts for low-copper and zero-copper Eco-Friction brake pads for vehicle platforms in North America and Europe
In North America and Japan the majority of passenger cars are fitted with Non-Asbestos Organic (NAO) brake pads, also known as ceramic brake pads. These pads provide low-noise operation and improved comfort. Pad and disc wear is lower and service life longer than Low-Steel formulations. However, NAO pads are less stable at maximum stress than Low-Steel and typically have a lower coefficient of friction.
Low-Steel brake pad formulations are preferred in Europe, where average speeds are higher and more aggressive performance is required. The pads’ lower iron content provides better friction at high speeds than other pad formulations.
Semi-metallic friction pad materials are sold by some aftermarket brands and are fitted as original equipment in certain passenger car markets and for pick-up trucks predominantly in North America. These contain no copper, but do not meet the high-speed performance or comfort noise requirements for some regional passenger car applications.