Epoxy microcapsules for high-performance self-healing materials using a novel method via integrating electrospraying and interfacial polymerization

The high-efficiency fabrication of high-quality microcapsules containing epoxy is crucial to the further development of the potential practical self-healing epoxy systems based on microencapsulated two-part epoxy-amine chemistry. Herein, a novel microencapsulation technique based on non-equilibrium droplets via integrating electrospraying and interfacial polymerization (ES-IP) was established to efficiently microencapsulate epoxy monomers. The ES-IP technique, consisting of three continuous steps, i.e. electrospraying to massively generate droplets, enwrapping every single droplet through instant interfacial polymerization, and thickening shell at an elevated temperature, has great flexibility to regulate the microencapsulation process and the microcapsule quality. The fabricated core-shell structured epoxy microcapsules (Ep-MCs) were comprehensively characterized for their properties, showing that they have high cleanness with rare impurities, controllable and tunable size, good thermal stability and tightness, and high effective core fraction. The high-quality Ep-MCs were adopted to formulate a self-healing epoxy based on the microencapsulated epoxy-amine chemistry. The highest healing efficiency, in terms of the recovered mode I fracture toughness, of 110 +/- 17% was achieved after being healed at room temperature (similar to 25 degrees C) for 48 h. While the developed ES-IP technique facilitates the microencapsulation technique based on non-equilibrium droplets, the fabricated high-quality Ep-MCs greatly promote the further developments of the practical self-healing materials. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.