Epoxy is the cured end product of epoxy resins, as well as a colloquial name for the epoxide functional group. Epoxy is also a common name for a type of strong adhesive used for sticking things together and covering surfaces, typically two resins that need to be mixed together before use. It can also be used as a solver due to its high melting and boiling points.
Epoxy resins, also known as polyepoxides are a class of reactive pre-polymers and polymers which contain epoxide groups. Epoxy resins may be reacted (cross-linked) either with themselves through catalytic homopolymerisation, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols, and thiols. These co-reactants are often referred to as hardeners or curatives, and the cross-linking reaction is commonly referred to as curing. Reaction of polyepoxides with themselves or with polyfunctional hardeners forms a thermosetting polymer, often with strong mechanical properties as well as high temperature and chemical resistance. Epoxy has a wide range of industrial applications, including metal coatings, use in electronic and electrical components, high tension electrical insulators, fibre-reinforced plastic materials, and structural adhesives commonly used in boat building. Epoxy resin is employed to bind gutta percha in some root canal procedures.
Popular consumer two-part epoxy adhesives for home, shop, and hobby are available in stores ranging in a wide selection of properties, including slow vs. fast curing time, opaque vs. clear colors, water-proof vs water-resistant, and flexible vs. rigid. A common misconception is that all epoxies are waterproof, however many – perhaps most – are not recommended for long-term submersion (such as flower vases) nor below the water line. Also, some epoxies bond better than others to different materials – even to different metals.