A novel repeated self-healing epoxy composite with alginate multicore microcapsules

Abstract

Herein, an epoxy (diglycidyl ether of bisphenol A) and a hardener (mercaptan/tertiary amine) were encapsulated within an alginate biopolymer to form self-healing multicore microcapsules. An electrospraying method produces dry microcapsules with diameters in the range of 300–400 μm, associated with a core content of 74% and 59% for epoxy and hardener microcapsules, respectively. Both microcapsules have a rough surface and multicore internal structures. The shell wall of both microcapsules varies around 3–6 μm. Thermogravimetric analysis (TGA) showed that these microcapsules could withstand temperatures up to 200 °C. Moreover, two types of self-healing systems were fabricated, i.e. dual-capsule and capsule-catalyst self-healing systems, where scandium(III) triflate was used as a catalyst. Both self-healing systems were assessed through the Charpy impact test. Healing was initiated at a capsule loading of 20 wt% and above for both healing systems. The dual-capsule self-healing system shows up to 4 healing cycles with healing efficiency in the range of 68–85%. Furthermore, the capsule-catalyst self-healing system achieves 2–3 healing cycles with healing efficiency in the range of 66–89%. Multiple healing is contributed by the multicore internal structure of capsules that can control the release of healing agents. Herein, it has been shown for the first time that alginate self-healing multicore microcapsules are able to provide multiple healing cycles to capsule-based self-healing composites.