Characteristics of urushi film prepared through thermal polymerization

Urushi (oriental lacquer) is a natural material that forms thin films with excellent durability and water resistance. There are two methods for curing urushi: oxidative and thermal polymerizations. Urushi is mainly applied to wood; therefore, the oxidative polymerization method has mainly been used to cure it. Oxidative polymerization requires temperature and humidity control and takes a long time to fully cure urushi. Urushi mixed with pigments has poor coloration. In contrast, the use of a thermal polymerization reaction can achieve curing in a short time. In this study, we focused on the thermal curing reaction of urushi, formed 13 different colored urushi coating films, and investigated their properties and coloration. We observed that urushi coatings produced through thermal polymerization took less time to cure than those produced through oxidative polymerization, and that urushi coatings with better coloration and high water repellency were obtained.