A asbestos type brake pad (replaced for NAO type due to carcinogenic risk)
B Non-asbestos friction materials are divided into the following categories:
(a) Semi-metallic friction materials for disc brake pads for passenger cars and heavy-duty vehicles. The material composition usually contains about 30% to 50% of ferrous metal materials (such as steel fiber, reduced iron powder, and foamed iron powder). Semi-metallic friction materials are therefore named. It was the first asbestos-free material developed to replace asbestos. Its characteristics: good heat resistance, high absorption power per unit area, large thermal conductivity, can be applied to the braking conditions of automobiles in high-speed and heavy-load operation. However, it has the disadvantages of large braking noise and fragile corners.
(b) NAO friction material. In a broad sense, it refers to non-asbestos-non-steel fiber friction materials, but the discs also contain a small amount of steel fibers. The base material in the NAO friction material is in most cases a mixture of two or more fibers (inorganic fibers with a small amount of organic fibers). Therefore, the NAO friction material is a non-asbestos mixed fiber friction material. Usually, the brake pad is a chopped fiber type friction block, and the clutch plate is a continuous fiber type friction plate.
(c) Powder metallurgy friction materials. Also known as sintered friction material, the iron-based and copper-based powdery materials are mixed, pressed, and sintered at a high temperature. Suitable for braking and transmission conditions at higher temperatures. Such as: aircraft, trucks, brakes and transmissions of heavy construction machinery. Advantages: long service life; disadvantages: high product price, large brake noise, heavy and brittle, and large wear and tear.
(d) Carbon fiber friction material. A type of friction material made of carbon fiber as a reinforcing material. Carbon fiber has the characteristics of high modulus, good heat conduction and heat resistance. Carbon fiber friction materials are among the best in all types of friction materials. The carbon fiber friction plate has high absorption power per unit area and light specific gravity. It is especially suitable for the production of aircraft brake pads. The brake pads of some high-end cars in foreign countries are also used. Because of its high price, its application range is limited and the output is small. In the carbon fiber friction material component, in addition to the carbon fiber, a compound of graphite and carbon is used. The organic binder in the component is also carbonized, so the carbon fiber friction material is also called carbon-carbon friction material or carbon-based friction material.