Self-healing epoxy nanocomposite coatings based on dual-encapsulation of nano-carbon hollow spheres with film-forming resin and curing agent

• Published in: Composites. Part B, Engineering Engineering, 2019-10, Vol.175, p.107087, Article 107087
• Main Authors: Haddadi, S.A., Ramazani S.A., A., Mahdavian, M., Taheri, P., Mol, J.M.C., Gonzalez-Garcia, Y.
• Format: Article
• Language: English
• Subjects: Carbon hollow spheres; Dual-capsule system; Epoxy; Polyamine; Self-healing
• ISSN: 1359-8368; 1879-1069
• DOI: 10.1016/j.compositesb.2019.107087

The ability of an active protective organic coating to restore its protection functionality in case of a coating defect is of pivotal importance to ensure durable performance under demanding corrosive conditions. In this paper, a self-healing epoxy system is fabricated by separate encapsulation of epoxy and polyamine in carbon hollow spheres (CHSs) and the autonomous healing performance of the system applied on mild steel is investigated. CHSs were synthesized via a silica templating method using carbonization of polysaccharide shells formed on the surface of silica templates. Consequently, epoxy and polyamine were loaded in separate capsules by dispersion of CHSs into the dilute solutions of epoxy/acetone and polyamine/acetone respectively, under vacuum conditions. The synthesized CHSs were characterized before and after the silica removal using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The CHSs loaded with the film forming agents were assessed using thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the protective and self-healing properties of the coatings fabricated were studied using electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) and salt spray testing. The results showed that scribe defects in epoxy coatings with 10 wt % epoxy and polyamine capsules were healed effectively upon efficient release and subsequent recombination of the epoxy and polyamine agents reforming a protective layer at the damaged region. [Display omitted] •Carbon hollow spheres (CHSs) were encapsulated with epoxy and polyamine agents.•Epoxy/polyamine doped CHSs were characterized by FTIR and TGA analyses.•Different contents of epoxy/polyamine doped CHSs were embedded in an epoxy matrix.•Doped CHSs-based epoxy nanocomposite coatings were applied on mild steel.•Self-healing performance of coatings was studied by salt spray, EIS and SVET tests.