RESUMEN
Single-layer isophorone diisocyanate (IPDI) are one of the most popular self-healing microcapsules but suffers from low shell strength, poor heat resistance, stability and aging properties. In this paper, IPDI microcapsules were encapsulated into double-layer phenolic (PF)/polyurethane (PU) by a two-step process involving interfacial polymerization and in-situ polymerization. The prepared microcapsule composites were comprehensively characterized for their physical and chemical properties using optical microanalysis, scanning electron microscope, Fourier transform infrared spectroscopy, thermal gravimetric analysis and depth-sensing indentation analysis. Compared with the single-layer PU-IPDI microcapsule counterpart, the mechanical performance, thermal resistance, aging property and environmental stability of double-layer PF/PU-IPDI microcapsules were significantly improved. The epoxy coating was enhanced with the incorporation of 10 wt.% PF/PU-IPDI microcapsules, whose self-healing performance was evaluated by scratch corrosion test. The results demonstrated successful repair of coating scratches, along with the absence of corrosion on the coated steel substrate soaked in a 10 wt.% NaCl solution for 7 days. By comparing the tensile strength of epoxy coating before and after crack formation, it could be found that the self-healing efficiency was 57.9% when loaded with 10 wt.% of PF/PU-IPDI microcapsules in coating. This study highlights that the rational design of double-layer microcapsules integrated into the epoxy coating matrix could provide excellent anti-corrosion and self-healing properties.
RESUMEN
Healing agent microcapsules have been used to realize self-healing for polymeric composites. In this work a novel kind of microcapsules encapsulating ethylenediamine (EDA) with epoxy resin as shell material were prepared by interfacial polymerization technology. The oil phase was epoxy resin prepolymer and carbon tetrachloride, and the water phase was EDA and deionized water. Under the action of emulsifier, a stable water-in-oil emulsion was formed. Then the emulsion was added to dimethyl silicone oil, stirred and dispersed, to prepare microcapsules. In addition, the factors affecting the preparation of microcapsules were studied. In this study, Fourier transform infrared(FTIR) was carried out to demonstrate the chemical structure of ethylenediamine microcapsules. Optical microscope(OM) and scanning electron microscope(SEM) were used to observe the morphology of microcapsules. Thermogravimetric analysis and differential scanning calorimetry were done to investigate the thermal properties of microcapsules. Permeability experiment and isothermal aging test were executed to verify the environment resistance of microcapsules. Results showed that EDA was successfully coated in epoxy resin and the microcapsule size was in the range of 50~630 µm. The synthesized microcapsules were thermally stable below 75 °C and perfect permeability resistance to ethanol solvent.