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. [Display omitted] •Ethylenediamine microcapsule was synthesized via interfacial polymerization in a water-in-oil emulsion.•The introduction of shell prepolymer can avoid the consumption of core material.•Polydimethylsiloxane as the continuous phase can effectively promote emulsion system stability.•Composites with embedded ethylenediamine microcapsules and epoxy microcapsules exhibited self-healing.