The performance characteristics of friction materials determine the production process
Phenolic resin is an important component in the structure of friction materials, and it is important to understand its process performance characteristics. Its molding process is divided into casting molding and molding. The production of phenolic friction material adopts the hot pressing forming process. Phenolic compression plastics are cured under heat and pressure for two reasons. The first is the fluidity factor of the pressed plastic. In the production of friction materials, in order to obtain the required friction performance and mechanical strength of the friction materials, usually in the formulation components, the dosage of fillers and fiber-reinforced materials should account for 80% to 90%, while the dosage of resin binders is only 80% to 90%. It accounts for 10% to 20%, so the fluidity of the pressed plastic is relatively poor. If the casting molding process is used, it is impossible to make the pressed plastic fill the wooden cavity to obtain a molded product.
We usually have to use a heating and pressure molding process, so that the compressed plastic flows under a certain pressure in the mold cavity heated to the curing temperature (170~180 ° C), fills the mold cavity, and is cured by heat, so as to obtain curing molding. product. The second is that the phenolic resin in the compression plastic further undergoes a polycondensation reaction at the curing temperature, and gradually changes from a linear structure or a branched structure to a three-dimensional cross-linked network structure, and finally achieves curing. During this process, the resin will release moisture and other low molecular substances, which will generate a large steam pressure at the molding temperature (150°C). If it escapes from the surface of the molded product, the product will be damaged and scrapped. Therefore, the product in the mold needs to maintain a high molding pressure before it is fully cured.
The characteristic of the thermoforming process is that the compression molding and heat curing of the compressed plastic are carried out simultaneously in the compression mold.
