An epoxide group consists of an oxygen atom bonded to two adjacent carbon atoms, forming a three-membered ring. In the context of epoxy resins, the epoxide group is usually part of a repeating structural unit, which is most commonly derived from bisphenol A or epichlorohydrin.
One of the most common epoxy resins is made by reacting bisphenol A with epichlorohydrin in a two-step process. In the first step, bisphenol A is reacted with epichlorohydrin to form a prepolymer, bisphenol A diglycidyl ether (BADGE). In the second step, the prepolymer is cured, or crosslinked, by heating it in the presence of a hardener (curing agent). The hardener typically contains an amine or an acid anhydride.
The following simplified chemical equation represents the reaction between bisphenol A and epichlorohydrin to form BADGE:
Bisphenol A + 2 Epichlorohydrin → Bisphenol A diglycidyl ether (BADGE) + 2 HCl
When cured, epoxy resins form a strong, rigid network of crosslinked polymers. Epoxy resins are widely used in a variety of applications, including adhesives, coatings, laminates, composites, and casting materials.
