Urea-formaldehyde microcapsule was produced by means of one step in-site polymerization.Optical microscope, scanning electron microscope and laser scanning confocal microscope (fluorescence tagged microcapsule shell) were used to analyze the size, shell thickness and structure of the microcapsule.The mechanical properties of the microcapsule was tested and analyzed by nano indentation test.The results showed that the dispersed and integrated microcapsules of 100 μm in diameter and 10 μm in shell thickness were produced with 45% core content.Young’s modulus of the microcapsule was a little lower than that of epoxy resin.When damage occurred in the epoxy resin matrix, the crack could rupture the microcapsule and release the repairing agent.
Microencapsulated healing agents that possess adequate strength,long shelf-life,and excellent bonding to the host material are required for self-healing materials. The in situ encapsulation method is demonstrated over an order of magnitude size reduction for the preparation of urea-formaldehyde(UF) capsules filled with a healing agent,a mixture epoxy resin of the epoxy 711 and E-51. Capsules with diameters as small as about 100 μm are achieved under the agitation rate of 800 r min-1. The capsules possess a uniform UF shell wall(4 μm average thickness) . By using the analysis of scanning electronic microscope(SEM) ,thermal analysis(TG-DTA) and FTIR,the characteristics of the microcapsules were investigated respectively. Successful self-healing has been demonstrated for anticorrosion covering materials with microcapsules.
