Preparation and characterization of tungsten oxide fortified poly(urea-formaldehyde) microcapsules for self-healing coatings

Radiation-resistant poly(urea-formaldehyde) (PUF) microcapsules with a bisphenol A diglycidyl ether/butyl glycidyl ether core were prepared via emulsion polymerization. Tungsten oxide (WO3) nanoparticles were incorporated into the polymer shell to improve radiation resistance of the resultant PUF microcapsules. Microcapsules prepared with modified WO3 nanoparticles had an average diameter of 117 μm, an encapsulation efficiency of 48%, and evenly dispersed nanoparticle incorporation of 3.5 wt%. Modification of dense WO3 nanoparticles was necessary for even dispersion into PUF microcapsule shells. The corrosion protection properties of epoxy films cast on mild steel were demonstrated via scratching and exposure to salt solution. Films containing modified WO3 fortified microcapsules demonstrated self-healing and retained corrosion protection properties. Under gamma irradiation, WO3/PUF microcapsules exhibited less degradation of epoxy healing core compared to microcapsules that were not fortified with WO3.