Preparation of Polyimide with Pendant Glycidyl Groups for Cationic Electrodeposition Coatings and Evaluation of Their Properties

Owing to the paradigm shift in energy systems from petroleum to electricity to realize sustainable society, the development of high-performance electrical devices has become increasingly important. The development of insulating materials with thermal stability and facile electrodeposition is essential for the production of high-performance next-generation electric devices because such electric devices cannot be coated with a conventional dip coating method. There are few reports on the development of polyimides with electrodeposition ability. Thus, we have reported that anionic electrodeposition coating was successfully performed using poly(amide acid) (PAA) nanoparticles that can be converted to polyimides (PI) upon thermal annealing. A hybrid coating using polyimide/bentonite with an inorganic filler was also produced, and the resulting electrodeposition films were thermostable at temperatures higher than 450 ℃. However, PAAs are usually subjected to hydrolysis, and so their pot life is not long. In this study, we developed cationic electrodeposition materials with solvent-soluble PIs with pendant epoxy groups. The developed materials served as good insulation coatings on substrates and exhibited excellent thermostability.