Abstract
In this study, we successfully manufactured polyurethane microcapsules containing isocyanate prepolymer as a core material for self-healing protection coatings via interfacial polymerization of a commercial polyurethane curing agent (Bayer L-75) and 1,4-butanediol (BDO) as a chain extender in an emulsion solution. With an optical microscope (OM) and a scanning electron microscope (SEM), the resulting microcapsules showed a spherical shape and an ideal structure with a smooth surface. Fourier transform infrared spectra (FTIR) showed that the core material was successfully encapsulated. Thermal gravimetric analysis (TGA) showed that the initial evaporation temperature of the microcapsules was 270 °C. In addition, we examined the influence of the concentration of the emulsifier and chain extender on the structure and morphology of the microcapsules. The results indicate that the optimal parameters of the microcapsule are an emulsifier concentration of 7.5% and a chain extender concentration of 15.38%. Microcapsules were added to the epoxy resin coating to verify the coating’s self-healing performance by a surface scratch test, and the results showed that the cracks could heal in 24 h. Furthermore, the self-healing coating had excellent corrosion resistance.
Highlights
Yang et al [34] prepared a kind of microcapsule with isophorone diisocyanate (IPDI) as the core material and polyurethane (PU) as the shell material by interfacial polymerization
Credico et al [36] used double-layer polyurethane/polyurea formaldehyde polyurethane (PUF) as the shell material and IPDI as the core material to prepare the microcapsule with a regular surface
As the core material of microcapsules for self-healing coatings, IPDI, is unstable, the reaction products had poor elasticity and low toughness because of the lack of soft segments, which can cause secondary damage. These shortcomings severely limited the development of IPDI microcapsules, so it is necessary to develop a microcapsule material with high elasticity and a high toughness repair agent
Summary
Microcapsule healing materials [1,2,3,4,5] have attracted increasing attention and have been widely researched, especially since the first-generation healing system reported by White et al [6] This is mainly because the microcapsule healing materials can provide instant feedback to external signals from the outside [7,8,9,10,11], complete the healing automatically and significantly extend the service life [12,13,14,15,16]. As the core material of microcapsules for self-healing coatings, IPDI, is unstable, the reaction products had poor elasticity and low toughness because of the lack of soft segments, which can cause secondary damage. These shortcomings severely limited the development of IPDI microcapsules, so it is necessary to develop a microcapsule material with high elasticity and a high toughness repair agent. The reaction process was controllable and significantly improved the reaction rate of the interfacial polymerization to form a membrane that could protect the core material from the water phase and reduce the loss of core material during the preparation of microcapsules. Our research has important implications for improving the practicality of microcapsule self-healing materials [40]
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