Wear characteristics of friction materials
In order to perform the braking and transmission functions well, we require the friction material to have a high and stable friction coefficient under different temperature conditions, under different moving speeds and loads, and also have good resistance to Abrasion and service life. The friction material has the following friction and wear characteristics.
1. Thermal recession
The matrix (ie, the binder) of the friction material is a thermosetting phenolic resin or rubber. When the friction plate is in the process of braking and transmission, the friction surface between it and the metal dual material will generate a very high temperature, reaching 200~400℃, or even higher. This has reached the thermal decomposition temperature region of resins and rubbers.
At this time, the macromolecules generate liquid or gaseous low-molecular substances due to thermal degradation, forming a thin liquid or gaseous medium layer on the friction surface, or the secondary medium layer only covers a part of the surface, making the original pure friction or dry friction The working condition becomes the case of mixed friction, which is reflected as a decrease or a sharp decrease in the coefficient of friction on the macroscopic level, which is called thermal recession. The thermal decay phenomenon can be clearly seen when the friction properties of the friction plate samples are measured by the friction tester.
2. Thermal wear and thermal cracking
When the friction plate is under high temperature working conditions for a long time, the thermal decomposition of resin or rubber macromolecules is intensified, the molecular main chain and cross-linked chain of the polymer are broken, the network structure is destroyed, and low molecular substances are produced and escaped. The result of thermal decomposition is carbonization and loss of quality of resins and rubbers. Carbonization makes the resin lose its cohesive effect, and the loss of quality reduces the amount of binders, resulting in the gradual formation of cracks on the surface of the friction lining, increasing the wear, and sometimes even the material falls off the surface of the friction lining and loses its working function.
Therefore, during the long-term high-temperature production (or transmission) work of the friction material, the thermal decomposition and thermal weight loss of the resin and rubber in the structure are intensified, the wear of the friction plate is intensified, and the service life is shortened.
From the above, it can be seen that the heat resistance of resin and rubber is very important to reduce the thermal recession, thermal wear and thermal cracking of the friction lining.
