| In the strong wind and sand flow environment of northwest China,the sand flow particles carried by the strong wind have caused severe erosion and wear damage to the windward sides of concrete structures,which will result in the surface shrinkage and cracking of the material,carbonization of the concrete and other phenomena,reducing the durability and functional practicability of the concrete structures,there by reducing the service life of railway bridges and causing serious traffic safety issues.If the surfaces of the concrete structures are coated with a protective material,the damage to the concrete structures can be reduced in an erosion environment,and the service life of t concrete structures will be significantly increased.Epoxy resins and their composite materials have good erosion resistance,with simple coating processes at low cost.therefore,epoxy resin are a kind of prime candidate materials for excellent protection of concrete structures in strong wind and sand flow areas.However,epoxy resins have the shortcomings of not self-healing,limiting their wide applications in the field of erosion and wear.If the epoxy resin protective materials have the self-repairing functions and their protective functions can be relf-restored,their applications can be significantly extended.In this paper,epoxy-solvent microcapsules were first prepared,and the coupling agent KH550 was added to modify the surface properties of the microcapsules.Secondly,the epoxy resin-solvent microcapsules were introduced into the epoxy resin E51 substrate,the final material was coated onto a solid surface,and then the damage(scratches)was artificially produced for testing.The epoxy resin-solvent microcapsule composite system was qualitatively evaluated to have self-healing ability.Intermittent erosion experiments were performed on the microcapsule/epoxy self-healing system,the effect of microcapsule content on the self-healing characteristics of the microcapsule self-healing system was analyzed,and the erosion mechanism of the microcapsule self-healing system was discussed.The change law of self-repairing performance under the conditions,proved that the system has the self-repairing characteristics even after multiple cycles.Because the polyurethane prepolymer has obvious toughening effect on the epoxy resin matrix material,which has practical significance in the engineering application of protective materials.Finally,an excellent microcapsule/epoxy resin self-repairing system was selected for toughening and modification of polyurethane.The feasibility of the epoxy resin-based solvent microcapsule composite self-repairing system was also proved in the sand erosion environment through experiments and tests.The following conclusions were reached based on experiments:(1)It can be seen that the core material ratio is 1: 9,the regulator NH4 Cl and resorcinol are respectively 1.25% by weight of the core material mass,the emulsifier is gum Arabic that the content is 0.5% by weight of the core material mass.The one-step in-situ polymerization method was converted to 1200 r /min in emulsification,the emulsification time was 20 min,the reaction was converted to 700 r /min,and the reaction time was 4 h.Epoxy-solvent microcapsules with a seemingly intact shape were prepared.Spherical,dense package,average volume is 63 ?m,core material content is 74.6%,conversion efficiency is 86.7%.According to the infrared test(FR-IR),Amino groups were successfully introduced on the surfacet.the microcapsule TG-DSC test shows that he surface modification of the coupling agent KH550 improves the thermal stability of the microcapsules,and the thermal stability temperature can reach 265 °C.(2)The experimental results show that the repair temperature,core material ratio,repair time and microcapsule content are the main factors affecting the self-repair performance of the microcapsule / epoxy resin system.It can be known that the epoxy resin-solvent(E51-EPA)microcapsule with a core material ratio of 1:9.the content of microcapsules in the excellent self-healing system at room temperature was determined to be 20 wt% and above,and the results showed that the composite coating has the characteristics of self-repair.(3)The intermittent cycling experiments of erosion wear results of the microcapsule / epoxy resin composite system show that with the increase of the number of erosion(mass of erosion particles),the erosion rate of the microcapsule / epoxy resin composite system gradually decreases,the erosion rate of the epoxy resin system tends to be consistent.Combined with the change in the Shore hardness value after erosion,and wear surface morphology observation of the erosion samples,It was found that the composite system with a microcapsule content of 20 wt% had complete multiple loop self-healing characteristics under the erosion environment.(4)Through the artificial scratch test of the polyurethane / microcapsule / epoxy composite system,and the intermittent cycling experiments of erosion wear,It was found that the addition of polyurethane improves the self-healing characteristics of the composite system under artificial scratch and erosion environment.Through wear surface morphology observation of the erosion samples,shows that the polyurethane / microcapsule / epoxy resin composite system with a polyurethane content of 5 wt% has better multiple loop self-healing characteristics.(5)The self-repair mechanism of each composite system under artificial scratch and erosion environment is similar.The basic process is: the composite system is subjected to artificial scratch or sand erosion,epoxy resin-solvent microcapsules in the composite system will be generated rupture,there by releasing the mixed liquid of E51 and EPA in the microcapsules.due to capillary action,the released core material will migrate to the crack.due to the swelling effect of EPA,the excess curing agent diethylenetriamine in the epoxy resin matrix.It migrates to the vicinity of micro-cracks and crosslinks with E51 in the core material to achieve self-healing of the composite coating. |
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