Preparation and Characterization of Microcapsules for Self-healing Materials

The urea-formaldehyde(UF) capsules filled with a healing agent, a mixture of epoxy resins(epoxy 711 and E-51) as core material, were produced by means of one step in-situ polymerization. The characteristics of these microcapsules were studied via scanning electron microscopy(SEM), particle size analysis, FTIR and DSC/TGA. The results show that the dispersed and integrated microcapsules of 5 mu m in shell thickness were synthesized successfully. The capsules were produced with diameters ranging from 10 to 250 mu m via controlling agitation rate. Young's modulus of the capsule was a little lower than those of the epoxy resins, but the microcapsules having such a shell thickness were robust enough to survive handling during manufacturing self-healing composites. When damage occurred in the epoxy matrix, the crack could rupture the microcapsule to make the repairing agent release.