Effectively enhance the corrosion protection of polyimide coating on CRS electrode by incorporation of small amount of electroactive aniline pentamer as pendant group

• Main Authors: Chih-Wei Lee, 李致瑋
• Other Authors: Jui-Ming Yeh
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/17523447416234346727

碩士 === 中原大學 === 化學研究所 === 105 === In this study, a series of electroactive polyimide containing pendant aniline pentamer was synthesized and characterized, followed by employed in anticorrosion coating application. First, aniline-pentamer (AP), pentamer-difluorobenzene (AP-DFB) and pendant electroacive-diamine monomer (P-DAM) were synthesized, followed by performing the structure characterization with LC-MS, FT-IR and 1H-NMR spectroscopy. The reversible redox capability of P-DAM can be further monitored by chemical approach (UV-visible absorption spectroscopy) and electrochemistry approach (cyclic voltammetry). Subsequently, for the preparation of electroactive polyimide, specific feeding ration of diamine for P-DAM and 4,4''-Oxydianiline (ODA) were dissolved in NMP. 4’-(4,4’-isopropylidene-diphenoxy) bis(phthalic anhydride) (BPADA) was introduced into the previous mixing solution. After heating treatment, pendant-electroactive poly(amic acid) (PAA) solution had made. After casting onto the surface of specific substrate, the electroactive polyimide (EPI 1, EPI3, EPI5) can be obtained by treating PAA with thermal imidization at specific programmed heating. The as-prepared electroactive polyimide was further characterized by FTIR spectroscopy. The redox capability of as-prepared electroactive polyimide containing different molar percentage of pendant aniline pentamer was further identified by cyclic voltammetry. However, based on the studies of viscosity for corresponding electroactive poly(amic acid), increasing the feeding molar ratio of pendant aniline pentamer in as-prepared electroactive polyimide may decrease the degree of polymerization of polymers, as reflecting by the decreasing of thermal/mechanical property of polymers (as evidenced by TGA and DSC data). It should be noted that, if the molar percentage feeding ratio of P-DAM excessed 5 mole%, the film formation of electroactive polyimide (EPI) was fail and became brittle. Therefore, following electrochemical corrosion of as-prepared EPI coating containing pendant aniline pentamer was focused on PI, EPI1, EPI3 and EPI5. For the investigation of anticorrosion properties of as-prepared EPI, the Tafel plots and electrochemical Impedance spectroscopy approach were used to study upon cold rolled steel (CRS) coupons. It should be noted that the EPI5, as compared to that of EPI1 and EPI3, was found to show the best corrosion protection upon CRS. Moreover, Nyquist/Bode plot was found to exhibit similar trend of corrosion protection. Redox capability of EPI coating upon underlying metal substrate was also found in this study, the densely passive metal oxides (Fe2O3 and Fe3O4) layers were induced by EPI and confirmed by Raman spectroscopy.