Preparation And Properties Of Microcapsules Containing Diluted Epoxy Resin For Self-healing Materials

Microcapsules have been widely used in the processing of self-healing materialsbecause of its special structure. In this work, a lot of attentions were paid to the formationprocedure of microcapsule, and the factors that can effect its formation have been takeninto consideration and have been decided by experiment. Properties of poly(urea-formaldehyde) microcapsules containing diluted epoxy resins have been test.Diluted epoxy resins was prepared by mixing epoxy resins (E-51) with1-Butylglycidyl ether (BGE), BGE made up15%of the mixture.The mixture can be dispersed bymachnical stirring, microcapsules wirh diameter less than50μm can be produced byusing SDBS as emulsifier and by stirring at1600rpm.Microcapsules filled with diluted epoxy resins were synthesized by two-step method.The conditions of preparation were decided by contrast experiment and were as follows:(1) Conditions for preparing pre-polymer of urea-formaldehyde resin：mole ratio: n(urea):n(formaldehyde)=1:1.8；Triethanolamine was used to control pH ofthe solution; pH value:8-10；Reaction time:1hour；Reaction temperature：70℃；(2) Conditions for microcapsules’ wall formation：Emusifiler solution：1.5wt%SDBSsolution；Reaction temperature：60-65℃；Stir ration：1600rpm；Reaction time:3-4hours；pH value of solution：3-3.5.Properties of microcapsules were further investigated. The formation procedure ofmicrocapsule was observed by optical microscope, and its theoretical formation procedurewas proved by observation and later test. Agitation rate has effect on the size ofmicrocapsules, and microcapsules with average diameter of38μm can be produced underagitation rate of1600rpm. FTIR (Fourier Transform Infrared Spectroscopy) analysis andobservation by optical microscope proved the success encapsulation of healing agent. ESEM (Environment Scanning Electron Microscope) analysis confirmed that the obtainedmicrocapsules have a rough surface, which is made by poly(urea-formaldehyde)(PUF)particles. The observation by environment scanning electron microscope also indicatesthat the obtained microcapsules have a good storage property, and the preparedmicrocapsules have a long service lifetime at room temperature. Microcapsules also havea good thermal property and won’t decomposed until246℃.