Epoxies are also thermosetting polymers and the diagram below illustrates the reaction between Bisphenol-A and Epichlorohydrin which combine to form the epoxy resin.

The condensation product of this reaction is HCl, and the polymerization also opens up the C -O - C ring in each epichlorohydrin molecule and hydrogen atoms attach to the unsatisfied bonds produced. A tri-functional co-reactant is required to produce a three dimensional epoxy network and this reacts with the hydrogen sites at each end of the resin building block.

Epoxies are used as adhesives and are common matrix materials for composites.

From: Askeland, "The Science of Engineering Materials,"
PWS (1994)