Film formation from cationic electropaint systems containing resins with different glass transition temperature

• Published in: Progress in organic coatings 2001-09, Vol.42 (3), p.209-217
• Main Authors: Suzuki, Yo-Ichiro, Fukui, Hirokazu, Tsuchiya, Kazuyo, Arita, Satoru, Ogata, Yukio H
• Format: Article
• Language: English
• Subjects: Applied sciences; Cationic electropaint systems; Coatings. Paints, varnishes and inks; Cu–Zn alloy; Deposited film; Exact sciences and technology; Film formation and curing, properties, testing; Film formation mechanism; Polymer industry, paints, wood; Resins
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/S0300-9440(01)00174-6

Some phenomena in the deposition process of electropainting have not been well elucidated till now. In this paper, to investigate an influence of glass transition temperature ( T g) on film formation, the deposited film was observed with an atomic force microscope and the electrochemistry was investigated, using two kinds of cationic acrylate resin with different T g (methyl methacrylate system (MMAs): T g=70°C, and methyl acrylate system (MAs): T g=5°C). Electrodeposition was performed under constant voltage or current condition. At constant voltage, the deposition behavior in the two resin systems differed extremely. The MMAs, the resin with high T g, produced a high resistance film. The MAs, the resin with low T g, was deposited forming a film at a voltage lower than 20 V. At constant current, the film formation did not result in a rise in voltage. It behaved like a conductive film. When the resin with high T g was used, particulate deposits were observed by AFM even in the induction period. The resin with low T g formed flat deposits. These results suggest that paint deposition is initiated once electrolysis of water starts. In addition, there are two types of film formation on the cationic electropainting: high resistance film formation for the resin with high T g, and ion-permeable film formation for the resin with low T g. In both cases, film growth occurs at the film/bulk solution interface.