Preparation of an Electronic-Grade Cardol-Based Epoxy Reactive Diluent By Stepwise Dichlorination

In this paper, electronic-grade epoxidized Cardol (E-Cardol), a bifunctional reactive diluent for epoxy resin, was synthesized from Cardol and epichlorohydrin by a two-step reaction. FT-IR, NMR, and high-performance liquid chromatography have been used for structural characterization and reaction dynamic studies. A stepwise dichlorination process considering all sources of chloride has been proposed: (i) minimizing the etherification side reaction while accelerating the main reaction, (ii) driving the main etherification reaction forward in the closed-loop reaction, and (iii) applying a refining step based on the Williamson reaction. E-Cardol with a hydrolyzable chlorine content below 100 ppm and decreased viscosity (30%) was obtained. Copper corrosion experiments confirmed the enhanced anticorrosion properties of the electronic-grade E-Cardol coating. This constitutes the first report of an electronic-grade Cardol-based bifunctional reactive diluent. Our work may give a guide to the design of all of the electronic-grade bio-based reactive diluents and other epoxy resins.