Orthophenolic molding compound (PMC for short) has a very broad meaning, usually including 40-60% phenolic resin, trade name NOVOLAC or RESOL, fillers (wood powder, mica, CaCO_3, glass fiber, etc.) and other additives. It belongs to thermosetting plastics, that is, the resin can be cured by increasing the temperature and pressure. The fully cured products cannot be heated to change their state, that is, they cannot be melted again.

The role of phenolic molding compound:

1. Phenolic resin is used as a binder in phenolic molding compounds. The basic requirements for the resin are:

(1), can meet the specific performance requirements of molded products.

(2) It must have good flow characteristics, that is, it is in a solid or semi-solid state that does not stick to hands under normal temperature and pressure. It has good fluidity under the pressing conditions, so that the molding material can evenly fill the molding cavity.

(3) Appropriate curing speed, with few by-products during the curing process, and good processability (such as good miscibility with various solvents).

2. Reinforced materials

The reinforcing material acts as a skeleton. Fibre reinforced materials are mainly used. In addition, chopped fiber mats, fiber fabrics or ropes are also used as reinforcement materials. Fiber-type reinforced materials include open-cut silk, untwisted roving, twisted yarn, high silica fiber, carbon fiber, asbestos fiber, nylon fiber, aramid fiber.

3. Auxiliary

Auxiliary agents include glass fiber surface treatment agents, fillers, thinners, mold release agents and pigments. The glass fiber surface treatment agent is used to improve the adhesion between the resin and the reinforcing material and the interface state between the resin and the fiber. For phenolic molding compounds, the commonly used glass fiber surface treatment agent is KH-550. The filler is mainly powdery filler, which is used to improve the fluidity of the molding compound, reduce the shrinkage of the molded product, improve the surface gloss of the product, uniform the quality of the product, and give the product a certain special performance. The thinner is used to reduce the viscosity of the resin and improve the impregnation performance of the resin.