Epoxy resins are low-molecular, oligomeric and polymeric epoxy compounds containing at least two epoxy groups in the structure, as well as cured products of these compounds. They are mainly produced in the synthesis of epichlorohydrin with bisphenol A or bisphenol F. Depending on the molar ratios of the substrates and condensation parameters, different types of these resins are made with various molecule sizes and numbers of epoxy and hydroxyl groups.
In uncured form, epoxy resins are viscous liquids or thermoplastic solids. Curing, or spatial cross-linking, is achieved by chemical reactions of the resin functional groups with an appropriate hardener. The cured material properties can be modified by the choice of the hardener.