Microcapsules of multilayered shell structure synthesized via one-part strategy and their application in self-healing coatings

The microcapsules of multilayered shells structure loaded with dicyclopentadiene (DCPD) were prepared via one-part strategy in Pickering emulsions stabilized by hydrolyzed poly(glycidyl methacrylate) (PGMA) nanoparticle. The target microcapsules had polyurethane (PU) inner shell layer, phenol-formaldehyde (PF) outer shell layer, and PGMA outermost layer. Meanwhile, in order to compare with the target microcapsules, the microcapsules of double layered shells (Sample 1) were both acquired. Size distribution, morphology, chemical structure and reaction heat of the capsules were studied by particle size analysis, scanning electron microscopy (SEM), fourier transform infrared spectra (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). It was found that the ingredients of PF, PU and PGMA were contained in the target microcapsules of multilayered shells, and the encapsulated core materials still kept high chemical reactivity. The resistant properties against thermal and solvent were evaluated by thermogravimetric analysis (TGA) and the solvent immersion test. When the IPDI content was suitable, the multilayered shells microcapsules (Sample 2, 3) possessed excellent thermal and solvent resistances comparing with Sample 1. In addition, the coatings embedded Sample 3 have displayed good self-healing performance by SEM, electrochemical impedance spectroscopy (EIS), salt immersion test and the tensile analysis of tapered double cantilever beam (TDCB) fracture specimens.