Brake Pad Formulation - Friction Material（二）
2. Technical requirements of friction materials
1. Appropriate and stable friction coefficient. The coefficient of friction is one of the most important performance indicators for evaluating any kind of friction material, and it is related to the performance of the transmission and braking functions of the friction plate. It is not a constant, but a number that changes due to the influence of temperature, pressure, friction speed or surface state and surrounding medium factors. The ideal coefficient of friction should have an ideal cold coefficient of friction and a temperature decay that can be controlled. Due to the heat generated by friction, the working temperature is increased, resulting in a change in the friction coefficient of the friction material.
2. Good wear resistance. The wear resistance of friction materials is a reflection of its service life, and it is also an important technical and economic index to measure the durability of friction materials. The better the wear resistance, the longer its service life. However, the wear of the friction material during the working process is mainly caused by the shear force generated by the friction contact surface. Operating temperature is an important factor affecting the amount of wear. When the surface temperature of the material reaches the thermal decomposition temperature range of the organic binder, organic binders such as rubber and resin will decompose, carbonize and lose weight. As the temperature increases, this phenomenon intensifies, the bonding effect decreases, and the amount of wear increases sharply, which is called "thermal wear".
3. Has good mechanical strength and physical properties. Before assembly and use of friction material products, machining such as drilling and riveting is required to make brake pad assemblies or clutch assemblies. In the process of friction work, the friction material not only has to withstand high temperature, but also bears relatively large pressure and shear force. Therefore, it is required that the friction material must have sufficient mechanical strength to ensure that no damage or fragmentation occurs during processing or use.
4. Low braking noise. Braking noise is related to the driving comfort of the vehicle, and it also causes noise pollution to the surrounding environment, especially to the urban environment. Brake noise is an important performance requirement for cars and city buses. As far as car disc pads are concerned, noiseless or low noise brake pads with good friction performance become the first product. With the development of the automobile industry, people are paying more and more attention to brake noise, and relevant departments have proposed standards. Generally, the noise produced by a car braking should not exceed 85 decibels.
3. Less wear on the counter surface. The transmission or braking function of friction material products must be realized through friction with the counterpart, that is, the friction disc (drum). During this friction process, the pair of friction couples will wear each other, which is a normal phenomenon. However, friction material products as consumable materials should not only wear as little as possible, but also wear less on the counter parts, that is, the service life of the counter parts should be relatively long. This fully demonstrates the characteristics of good friction performance. At the same time, during the friction process, the surface of the counterpart, that is, the friction disc or the brake drum, should not be ground into heavy scratches, scratches, grooves and other transitional wear conditions.
