A highly responsive healing agent for the autonomous repair of anti-corrosion coatings on wet surfaces. In operando assessment of the self-healing process

• Published in: Journal of materials science Vol. 56; no. 2; pp. 1794 - 1813
• Main Authors: Koochaki, Mohammad Sadegh, Khorasani, Saied Nouri, Neisiany, Rasoul Esmaeely, Ashrafi, Ali, Trasatti, Stefano P., Magni, Mirko
• Format: Journal Article
• Language: English
• Published: New York Springer US 2021; Springer; Springer Nature B.V
• Subjects: Acrylonitrile; Amines; Analysis; Catechin; Catechol; Characterization and Evaluation of Materials; Charge transfer; Chemistry and Materials Science; Classical Mechanics; Coatings; Corrosion; Corrosion prevention; Crystallography and Scattering Methods; Dopamine; Electrochemical impedance spectroscopy; Embedding; Encapsulation; Epoxy resins; Fourier transforms; Grafting; Infrared spectroscopy; Isocyanates; Materials Science; Metals & Corrosion; Microencapsulation; NMR spectroscopy; Nuclear magnetic resonance spectroscopy; Polyamides; Polyethers; Polymer Sciences; Polystyrene resins; Scanning electron microscopy; Self healing materials; Solid Mechanics; Spectrum analysis; Steel; Thin layer chromatography; Underwater
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-020-05332-9

A methodology to enrich epoxy coatings of an effective self-healing feature on wet surfaces was developed as a further step on for practical corrosion protection issues. To this aim, a polyetheramine was chemically engineered by grafting catechol units and then successfully encapsulated in microcapsules (MCs) to be finally embedded into an epoxy resin deposited on steel panels. Fourier transform infrared spectroscopy (FTIR), thin-layer chromatography, and 1D and 2D nuclear magnetic resonance spectroscopy confirmed the successful polyetheramine modification by dopamine units. Different dosages of catechol-modified polyetheramine were encapsulated within poly(styrene-co-acrylonitrile) shell via electrospray method to study the influence of dopamine grafting on the healing performance. Scanning electron microscopy (SEM) analysis revealed the formation of the spherical MCs, while FTIR and TGA analyses confirmed the successful encapsulation. The highly responsive self-healing coatings were then prepared by embedding amine- and isocyanate-containing MCs (1:1 weight ratio; 3 wt% overall) as a dual-capsule system exploiting the polyurea formation as a fast healing reaction. In operando electrochemical impedance spectroscopy (EIS) tests were employed to study the underwater self-healing performance. According to the EIS results, monotonically increasing variation with time of the charge transfer resistance was correlated with a fast and effective underwater self-healing performance for the sample using 40 wt% of a catechol-modified healing agent. Such results, combined with others including SEM investigation on the underwater healed samples, point to an improved adhesion of the growing dopamine-bearing polymer to both underlying metal and epoxy edges of the scratch. Graphic abstract