Glycidyl Ether Properties

Glycidyl Ethers of resorcinol have been shown to have excellent hot strength, even when cured at room temperature they are capable of giving the strength required by US specification.

Wynstra et al. in discussing the effect of the structure of the resin on elevated temperature performance (measured as the flexural strength of a laminate), point out the importance of the overall functionally of the resin/hardener system. But the various characteristics of the molecules, such as the distance between functional groups and the ratio of functionally to molecular weight, are clearly other factors that have an influence on hot-strength.

Since the phenolic hydroxyl group is not involved in the reaction between phenol and formaldehyde, phenolic resin can be converted into glycidyl polyester and formaldehyde, phenolic resin can be converted into glycidyl polyesther by reaction with epichlorohydrin. Phenolic resins of the novolak type are of most interest, and the polyepoxides of ortho-cresol formaldehyde novolak are stated to be of significant importance as adhesives for use in the 316o temperature range.

The properties of an epoxy novolak adhesive cured with pyromellitic dianhydride, and also of an epoxy novolak modified silicone/phenolic adhesive, are described in an informative paper by Janis. Adhesive applications of epoxy resins from low stage phenolic novolaks have been studied by George and Rao; the resins were cured with an aromatic diamine at an elevated temperature and tested in wood, aluminum and wood to aluminum joints.