Epoxy resins all contain epoxy groups, so the properties of epoxy resins and their cured products are similar, but there are many kinds of epoxy resins. Different types of epoxy resins have large differences in carbon frame structure, and their properties are different. . The same type and different grades of epoxy resin have different physical and chemical properties such as viscosity, softening point and chemical reactivity due to differences in molecular weight and molecular weight distribution. Even for the same type of epoxy resin of the same type, the properties of the cured product vary depending on the curing agent and the fixed-line process. That is to say, the properties of the epoxy resin are related to its molecular structure, preparation process and resin composition, and the properties of the cured product are also related to the type and molecular structure of the curing agent, and the curing process.