Preparation And Properties Of Microcapsules In The Water-based Self-healing Coatings

At present, the coatings is used widely, and the water-based coatings withenvironmentally friendly features become the future direction of the paint. Theeconomic costs is huge when the paint surface damages due to external factor. The self-healing in coatings can repair surface with microcracks because of external stress,improve the life of the coating, and reduce the economic and social costs of repair. Inthis paper the purpose is order to optimizing the synthetic process in preparingmicrocapsules for using in waterborne self-healing coatings and explore preliminarypreparation and characterization of water-based coatings.In this paper, the epoxy resin microcapsules are prepared in situ polymerizationwith two-step. The urea-formaldehyde resin is as shell case and epoxy resin is as coreof microcapsules. The crafts are optimized in studying some factors having influencein preparation microcapsules. Such as the molar ratio of urea to formaldehyde, thestirring speed, the ratio of mass of the wall to the core and the viscosity of epoxy resinin the microcapsules. The size distribution and shape of microcapsules is observed byoptical microscopy (OM). The surface morphology and wall thickness of microcapsulesis observed by scanning electron microscopy (SEM). Thermal properties of themicrocapsules were analyzed by thermal gravimetric analysis (TG) and differentialscanning calorimetry (DSC). The structure of microcapsules were characterized byfourier transform infrared spectroscopy (FTIR). The epoxy resin microcapsules incoatings are obtained. The particle diameter is473μm~840μm. The wall thickness ofabout125um. The content of core in microcapsules is59.73%. The rate of covering is15.27%. The microcapsules have the good thermal stability and they begin todecompose at250℃.In this paper, the epoxy resin and fluorocarbon resin microcapsules are preparedin situ polymerization with two-step. The urea-formaldehyde resin is as shell case andepoxy resin and fluorocarbon resin is as core of microcapsules. The crafts are optimizedin studying some factors having influence in preparation microcapsules. Such as theviscosity of composite resin in the microcapsules, the stirring speed, the end of the pHin the reaction system and the concentration of emulsifier with sodium dodecyl benzenesulfonate. The size distribution and shape of microcapsules is observed by opticalmicroscopy (OM). The surface morphology and wall thickness of microcapsules isobserved by scanning electron microscopy (SEM). Thermal properties of the microcapsules were analyzed by thermal gravimetric analysis (TG) and differentialscanning calorimetry (DSC). The structure of microcapsules were characterized byfourier transform infrared spectroscopy (FTIR). The epoxy resin and fluorocarbon resinmicrocapsules in coatings are obtained. The particle diameter is300um~700μm. Thewall thickness of about160um. The content of core in microcapsules is59.84%. Therate of covering is25.63%. The microcapsules have the good thermal stability and theybegin to decompose at250℃.Finally, the water-based self-healing coatings is prepared and characterizedpreliminarily. The quality of the microcapsules in the waterborne self-healing coatingsis controlled between9%~13%. Which can repair microcracks in50μm~150μm.