Microencapsulation of ethylenediamine and its application in binary self-healing system using dual-microcapsule

Microencapsulation of healing agents has been applied to realize the self-healing function of polymeric composites. In practice, however, microencapsulation of a liquid amine is very complicated because it is soluble in water and most organic solvents. In this paper, we report a new approach to preparing amine microcapsules that constitute a dual-microcapsule epoxy-amine self-healing system for epoxy composites. Ethylenediamine (EDA)-containing microcapsule with epoxy-EDA shell was successfully synthesized via interfacial polymerization in a water-in-oil emulsion. There were three key factors to solve the problem of microencapsulated a liquid amine, including preparation of epoxy-EDA shell prepolymer, a small amount of deionized water into core material, and polydimethylsiloxane as the continuous phase. A series of methods including Fourier transform infrared, differential scanning calorimetry, optical microscope, and scanning electron microscope were carried out to prove that microcapsules were suitable for preparing self-healing composites. Healing efficiency of self-healing epoxy achieved to 80.4% with 12 wt% epoxy-containing microcapsules and 8 wt% EDA-containing microcapsules. In general, this work provides a novel preparation method of liquid amine microcapsules. This novel and effective self-healing system may be useful for the development of epoxy-based structural composites for various applications.