A highly responsive healing agent for the autonomous repair of anti-corrosion coatings on wet surfaces. In operando asse
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A highly responsive healing agent for the autonomous repair of anti-corrosion coatings on wet surfaces. In operando assessment of the self-healing process Mohammad Sadegh Koochaki1,2 , Saied Nouri Khorasani1,* Ali Ashrafi4 , Stefano P. Trasatti2 , and Mirko Magni2,* 1
Department Department 3 Department Iran 4 Department 2
, Rasoul Esmaeely Neisiany3
,
of Chemical Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran of Environmental Science and Policy, Università Degli Studi Di Milano, 20133 Milan, Italy of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University, Sabzevar 9617976487, of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran
Received: 22 June 2020
ABSTRACT
Accepted: 8 September 2020
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.
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The Author(s) 2020
Handling Editor: Maude Jimenez.
Address correspondence to E-mail: [email protected]; [email protected]
https://doi.org/10.1007/s10853-020-05332-9
J Mater Sci
GRAPHIC ABSTRACT
Introduction Nowadays, several self-healing techniques have been developed as promising approaches for increasing the service life of the organic coatings via controlling the crack propagation in their matrix [1–4]. Although many of the reported self-healing materials have shown
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