Epoxy is characterized by a three-membered ring known as the epoxy, epoxide, oxirane, or ethoxyline group. Commercial epoxies contain aliphatic, cycloaliphatic, or aromatic backbones. Treatment with curing agents gives insoluble and intractable thermoset plastics [thermosetting plastic]. They are prepared by the reaction of compounds containing an active hydrogen group with epichlorohydrin followed by dehydrohalogenation or by direct epoxidation of olefins by peracids.