Structure and composition of friction materials(一)
Friction material is a polymer ternary composite material, it contains three parts: (1) the polymer compound as a binder; (2) This inorganic or organic fiber as the weakening component; (3) to the filler as a friction performance regulator or compound.
1. The organic binder used for friction materials is phenolic resin and rubber preparation, so phenolic resin is mainly used. Their characteristics and effects are that if they are in a certain heating temperature, they first become loose and then turn into a viscous fluid state, causing movement and homogenizing the matrix of the material originated from the material. Finally, through the rubber vulcanization of resin curing, the fiber and the filler are bonded together. To produce a hard material with considerable strength and can meet the performance of the friction material recommended friction sheet products. For friction materials, the heat resistance of resin and rubber is a very key performance index. Because the vehicle and machinery in the braking and transmission work, the friction plate in 200℃ ~ 450℃ under high temperature conditions. In this temperature range, the main part of the fiber and filler is inorganic type, never erupt thermal decomposition. So for resins and rubbers, organic ones, they also move into the thermal decomposition zone. At this time, various performance indexes of friction materials will break out favorable changes (friction coefficient, damage, mechanical strength, etc.), especially the three cooling (thermal decay, thermal expansion, thermal cracking) phenomenon in the process of detection and use of friction materials, which is caused by the thermal decomposition of resin, rubber and organic materials. Therefore, the selection of resin and rubber for the performance of friction materials has a very key role. Using different binders will result in different frictional and structural properties. Phenolic resin and modified resin are used at present. Such as: cashew shell oil modification, nitrile powder modification, rubber modification and other modified phenolic resin as a friction material binder. The quality requirements for resin are: (1) poor heat resistance, relatively bad thermal decomposition temperature and relatively high thermal weight loss. (2) powdery resin fineness is low, usually 100 ~ 200 mesh, the worst is more than 200 mesh, contribute to the uniformity of mixing concentration, can reduce the amount of resin in the formula. (3) The content of free powder is high, and 1% ~ 3% is appropriate. (4) Suitable curing speed 40s ~ 60s (150℃) and flow distance (120℃ 40 ~ 80mm)
