26 - Epoxide Resins

Abstract

The epoxide resins also known as epoxy resins and, occasionally, as ethoxyline resins, are characterized by the possession of more than one 1,2-epoxy group per molecule. This group may lie within the body of the molecule but is usually terminal. The three-membered epoxy ring is highly strained and is reactive to many substances, particularly with proton donors. Such reactions allow chain extension and/or cross-linking to occur without the elimination of small molecules such as water, that is, they react by a rearrangement polymerization type of reaction, in consequence, these materials exhibit a lower curing shrinkage than many other types of thermosetting plastics. There is a scope or a very wide range of epoxy resins. The nonepoxy part of the molecule may be aliphatic, cycloaliphatic, highly aromatic hydrocarbon, or it may be non-hydrocarbon and possibly polar. It may contain unsaturation. Similar remarks also apply to the chain extension/cross-linking agents, so that cross-linked products of great diversity may be obtained. However, the commercial scene is dominated by the reaction products of bis-phenol A and epichlorohydrin, which have some 80%-90% of the market share. In the early stage of their development the epoxy resins were used entirely for surface coating.