Enzymatic epoxidation and polymerization of cardanol obtained from a renewable resource and curing of epoxide-containing polycardanol

Epoxide-containing polycardanol was enzymatically synthesized via two routes using two different enzymes, viz. lipase and peroxidase. Lipase catalysis was used for the epoxidation of the unsaturated alkyl chains of both cardanol and polycardanol. Peroxidase catalysis was used for the polymerization of both cardanol and epoxide-containing cardanol. One route was the synthesis of epoxide-containing cardanol from cardanol, hydrogen peroxide and an organic acid in the presence of lipase, followed by the polymerization of the phenolic functional groups of cardanol using peroxidase. In the other route, polymerized cardanol was prepared from cardanol and hydrogen peroxide in the presence of peroxidase and, subsequently, the epoxide-containing polycardanol was synthesized from polycardanol, hydrogen peroxide and an organic acid in the presence of lipase. NMR and IR spectroscopy confirmed the polymer structure, and the former route yielded epoxide-containing polycardanol in a higher yield of over 90%. The curing of the resulting polymers proceeded thermally at 150 °C, yielding transparent polymeric films with a high gloss surface within 3 h. The pencil scratch hardness of the present films was improved compared with that of polycardanol. Owing to the epoxide contained in the polymerized cardanol, the film cured with phenalkamine showed a higher hardness value after a relatively short curing time.