Phenolic resin (PF) is a thermosetting plastic formed by the condensation polymerization of phenol and formaldehyde. It can be regarded as “the pioneer of synthetic plastics for humans and the king of insulation” - it forms a three-dimensional network structure through the cross-linking of phenol and formaldehyde under the action of a catalyst, thus having extremely high heat resistance (able to be used for a long time at 150-200°C), excellent electrical insulation properties, flame retardancy, and resistance to erosion by acid and alkali solvents (but poor resistance to strong oxidants), and good dimensional stability. Phenolic resin not only has high hardness and resistance to creep, but also can be compounded with fillers such as wood powder and glass fibers to form molding plastics, and is widely used in electrical switches and sockets, handles, pot handles, insulation layers of electronic components, brake pads, grinding wheel adhesives, and the shells of old-style telephones, etc., in situations that require heat resistance and insulation.