Overview
Self-healing materials repair damage without outside intervention. In coatings, the main goal is to reseal scratches and microcracks so that corrosion cannot start at damaged sites. Most practical work uses microcapsules dispersed in the coating that rupture when the film is damaged.
Key findings
- The landmark 2001 study embedded microcapsules of a healing monomer and a separate catalyst in an epoxy. A crack ruptured the capsules, the released agent polymerized in the crack, and the material recovered a large share of its original fracture toughness.[1]
- Isocyanate (IPDI) can be microencapsulated in polyurethane shells to give catalyst-free healing triggered by moisture, a natural fit for humid or wet service, with capsules retaining most of their core during months of storage.[2]
- Coatings containing microencapsulated healing agents were shown to repair scratches, passivate the exposed substrate and prevent corrosion in both model and industrially relevant systems.[3]
- Microvascular networks that deliver healing agent through channels can support repeated healing of the same damage site.[4]
- Self-healing approaches fall into capsule-based, vascular and intrinsic (reversible-chemistry) families, which differ in how often and how much damage they can repair.[5]
- Reviews of capsule-based coatings and of smart protective coatings survey shell chemistries, healing agents and encapsulation methods.[6][7]
What it means in the field
For specifiersToday’s capsule-based systems mainly add protection at scratches and small damage, often only once per site, and capsule loading can change film properties. Ask for scribed salt-spray or electrochemical test data, and treat self-healing as a bonus layer of protection, not a substitute for proper film thickness and surface prep.
References
- White SR, Sottos NR, Geubelle PH, et al. (2001). Autonomic healing of polymer composites. Nature, 409(6822), 794–797. doi:10.1038/35057232
- Yang J, Keller MW, Moore JS, et al. (2008). Microencapsulation of isocyanates for self-healing polymers. Macromolecules, 41(24), 9650–9655. doi:10.1021/ma801718v
- Cho SH, White SR, Braun PV (2009). Self-healing polymer coatings. Advanced Materials, 21(6), 645–649. doi:10.1002/adma.200802008
- Toohey KS, Sottos NR, Lewis JA, et al. (2007). Self-healing materials with microvascular networks. Nature Materials, 6(8), 581–585. doi:10.1038/nmat1934
- Blaiszik BJ, Kramer SLB, Olugebefola SC, et al. (2010). Self-healing polymers and composites. Annual Review of Materials Research, 40, 179–211. doi:10.1146/annurev-matsci-070909-104532
- Samadzadeh M, Hatami Boura S, Peikari M, et al. (2010). A review on self-healing coatings based on micro/nanocapsules. Progress in Organic Coatings, 68(3), 159–164. doi:10.1016/j.porgcoat.2010.01.006
- Zhang F, Ju P, Pan M, et al. (2018). Self-healing mechanisms in smart protective coatings: a review. Corrosion Science, 144, 74–88. doi:10.1016/j.corsci.2018.08.005
Citations were checked against publisher, DOI or agency records. Summaries are paraphrased; read the original papers for full methods and data.