The performance characteristics of friction materials determine the manufacturing process
Phenolic resin is an important component in the structure of friction materials. It is important to understand its technological properties. The molding process can be divided into casting and molding. Phenolic friction materials are produced by hot pressing process. There are two reasons for phenolic pressure plastics curing under heating and pressure. The first is the fluidity factor of pressure plastics. In the production of friction materials, in order to make the friction materials obtain the required friction properties and mechanical strength, the amount of filler and fiber reinforced materials usually accounts for 80%~90% of the ingredients in the formula, while the amount of resin adhesive only accounts for 10%~20%, so the fluidity of the pressure plastics is relatively poor. If the casting molding process is adopted, the molded products cannot be obtained by filling the wood cavity with pressure plastics.
Generally, we must use the molding process of heating and pressurization to make the pressurized plastic flow in the mold cavity heated to the curing temperature (170~180 ℃) under a certain pressure, fill the mold cavity, and be cured by heat, so as to obtain the cured molded products. The second is that the phenolic resin in the pressure plastic undergoes further polycondensation at the curing temperature, gradually changing from linear structure or branched chain structure to three-dimensional cross-linked network structure, and finally achieving curing. In this process, the resin will release water and other low molecular substances, which will generate large steam pressure at the molding temperature (150 ℃). If they escape from the surface of the molded products, the products will be damaged and discarded. Therefore, the products in the mold need to maintain high molding pressure before fully curing.