writer：Dawei Sun, Jinliang An, Gang Wu, Jinglei Yang
keywords：Hexamethylene diisocyanate，Microcapsule，Shell tightness，Thermal stability;
source：期刊
specific source：Journal of Materials Chemistry A
Issue time：2015年
Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have  been  successfully  synthesized  via  interfacial  polymerization reaction in an oil-in-water emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The reaction parameters including reaction temperature (40°C, 50°C, 60°C), reaction duration (1h, 1.5h, 2h and 2.5h), the amount of Suprasec 2644 (2.4g, 3g and 3.6g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with the increase of reaction temperature, reaction duration, the mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvents resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6 % weight  loss compared with pure HDI with 90 % weight  loss after 60 min isothermal treatment at 100 °C. After immersion in various solvents for 24 days, the microcapsules released as low as ~3% of core in weakly polar solvents (i.e. hexane and xylene), about 5% - 60% core in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60% - 90% in water and polar protic solvents (i.e.  isopropanol and ethylene glycol). Both fresh and hexane  treated HDI-capsules  showed  excellent  anticorrosion performance  in  the  scratched coatings via self-healing functionality,  indicating  promising  practical  application  in  industrial coating and paint systems.