Abstract
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.
Highlights
With the development of modern civilization, the application of composite materials is more and more extensive, and the technology is more and more mature
Fereidoon et al.[26] prepared DCPD microcapsules with the urea-formaldehyde resin acting as shell materials which were modified by carbon nanotubes and aluminum oxide nanoparticles to improve the water resistance and thermal resistance of microcapsules
There are several issues existed in these self-healing microcapsules systems, one is that the shell materials of microcapsules usually is different with the matrix of epoxy-based composites, so there is an interface problem between shell materials of microcapsules and composites, when the crack tip extends to the vicinity of microcapsule, it maybe expand along the interface between microcapsules and epoxy resin, making the microcapsule fail to fracture and lose the self-healing function
Summary
With the development of modern civilization, the application of composite materials is more and more extensive, and the technology is more and more mature. The first one is that epoxy resin prepolymer is introduced to accelerate the polymerization reaction speed of epoxy resin to form compact shell material, prohibiting the EDA from volatilizing, and the second one is a small amount of deionized water is added to EDA to form complex, and stable emulsion of water-in-oil is prepared successfully. In order to explore the optimal synthesis process of EDA microcapsules, orthogonal experiments were designed by selecting four influencing factors: raw material ratio, stirring speed, type of emulsifier and reaction time.
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