These materials are based on the reactive oxirane group, which are characterized by the attachment of one oxygen atom to two different adjacent carbon atoms. Standard epoxy resins are the reaction product of bisphenol A and epichlorohydrin. Curing of epoxy resins generally occurs at ambient temperatures and is achieved by the chemical reaction of the epoxy with a second reactant such as amines, polyamines, amine products, or other reactants. Cure can occur at higher temperatures when reacted with anhydrides, carboxylic acids, phenol or novolac (phenol-formadehyde) thermoplastic resins. These reactants are sometimes referred to as catalysts, which is a misnomer.