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Open AccessArticle

Design Strategy for Self-Healing Epoxy Coatings

1
Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
2
Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
*
Author to whom correspondence should be addressed.
Coatings 2020, 10(1), 50; https://doi.org/10.3390/coatings10010050
Received: 25 November 2019 / Revised: 27 December 2019 / Accepted: 3 January 2020 / Published: 6 January 2020
(This article belongs to the Special Issue Self-Healing Coatings and Films)
Self-healing strategies including intrinsic and extrinsic self-healing are commonly used for polymeric materials to restore their appearance and properties upon damage. Unlike intrinsic self-healing tactics where recovery is based on reversible chemical or physical bonds, extrinsic self-healing approaches rely on a secondary phase to acquire the self-healing functionality. Understanding the impacts of the secondary phase on both healing performance and matrix properties is important for rational system design. In this work, self-healing coating systems were prepared by blending a bio-based epoxy from diglycidyl ether of diphenolate esters (DGEDP) with thermoplastic polyurethane (TPU) prepolymers. Such systems exhibit polymerization induced phase separation morphology that controls coating mechanical and healing properties. Structure–property analysis indicates that the degree of phase separation is controlled by tuning the TPU prepolymer molecular weight. Increasing the TPU prepolymer molecular weight results in a highly phase separated morphology that is preferable for mechanical performances but undesirable for healing functionality. In this case, diffusion of TPU prepolymers during healing is restricted by the epoxy network rigidity and chain entanglement. Low molecular weight TPU prepolymers tend to phase mix with the epoxy matrix during curing, resulting in the formation of a flexible epoxy network that benefits TPU flow while decreasing Tg and mechanical properties. This work describes a rational strategy to develop self-healing coatings with controlled morphology to extend their functions and tailor their properties for specific applications.
Keywords: self-healing coating, structure property relationship, bio-based epoxy self-healing coating, structure property relationship, bio-based epoxy
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MDPI and ACS Style

Yuan, D.; Solouki Bonab, V.; Patel, A.; Yilmaz, T.; Gross, R.A.; Manas-Zloczower, I. Design Strategy for Self-Healing Epoxy Coatings. Coatings 2020, 10, 50.

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