Novolac Epoxy Resin 638 for heat resistance coatings Novolac Epoxy Resin (638) General description 638 is a semi-solid reaction product of epichlorohydrin and phenol-formaldehyde novolac. It has advantageous characteristics of good adhesion strength, excellent heat and chemical resistance because of its multi-functional groups in one molecule fully cross-linked. Therefore, it has excellent physical properties in addition to the basic reactivity of general Epoxy Resin.