(一) Definition of Epoxy Resin
Epoxy resin is a type of polymer compound. Its molecular chain contains at least two epoxy groups and it belongs to the category of thermosetting resins. Among them, bisphenol A - type epoxy resin is the most representative.
(二) Characteristics of Epoxy Resin (Taking Bisphenol A - type as an Example)
Epoxy resin has limited value when used alone and needs to be combined with a curing agent to exert its practical value.

• It has high adhesive strength, ranking among the top in synthetic adhesives.
• The curing shrinkage rate is small. It is one of the adhesives with the lowest shrinkage rate, which is also one of the reasons for its high adhesive strength after curing. For example, the shrinkage rate of phenolic resin adhesive is 8 - 10%, that of silicone resin adhesive is 6 - 8%, that of polyester resin adhesive is 4 - 8%, while that of epoxy resin adhesive is only 1 - 3%. After modification, the shrinkage rate can be further reduced to 0.1 - 0.3%, and the coefficient of thermal expansion is 6.0×10⁻⁵/℃.
• It has excellent chemical resistance. The ether groups, benzene rings, and aliphatic hydroxyl groups in the cured system are not easily eroded by acids and alkalis, allowing it to be used for a long time in various corrosive media.
• It has good electrical insulation performance, with a breakdown voltage that can exceed 35 kv/mm.
• It has stable processing performance. The products have precise dimensions, good durability, and a low water absorption rate.
  However, bisphenol A - type epoxy resin also has some disadvantages, such as high operating viscosity, brittle cured physical properties, small elongation, low peel strength, and poor resistance to mechanical and thermal shock.

(三) Application and Development History of Epoxy Resin

• Development History: Epoxy resin was patented in Switzerland by P.Castam in 1938. Ciba Company developed the earliest epoxy adhesive in 1946, and in 1949, S.O.Creentee in the United States developed epoxy coatings. China started the industrial production of epoxy resin in 1958.
• Application Fields:
  • Coatings Industry: Widely used in industries such as pipelines, containers, automobiles, ships, aerospace, electronics, toys, and handicrafts.
  • Electronic and Electrical Industry: Used for electrical insulation materials, such as the sealing and pouring of rectifiers and transformers, and the sealing and protection of electronic components.
  • Hardware Accessories, Crafts, and Sporting Goods Industries: Used for products such as nameplates, accessories, trademarks, hardware, rackets, and fishing gear.
  • Optoelectronic Industry: Used for the encapsulation, pouring, and bonding of products such as light - emitting diodes, digital tubes, and electronic displays.
  • Construction Industry: Used in projects such as roads, bridges, floors, steel structures, wall coatings, and dams.
  • Adhesives, Sealants, and Composite Materials Fields: Used for the bonding and compounding of various substances, such as wind turbine blades, ceramics, and glass.