Encapsulation of Cerium Nitrate within Poly(urea-formaldehyde) Microcapsules for the Development of Self-Healing Epoxy-Based Coating

Abstract

In order to study the release of cerium nitrate in a self-healing epoxy-based coating, poly (urea-formaldehyde) (PUF) microcapsules containing cerium nitrate were synthesized. The effects of healing agent concentration and weight percent of microcapsules in the epoxy resin were studied through the incorporation of microcapsules within an epoxy-based coating. The prepared microcapsules were characterized using thermogravimetric analysis and Fourier transform infrared spectroscopy and confirmed the successful encapsulation of cerium nitrate within PUF capsules. The self-healing performance of the prepared epoxy coating was investigated in 0.6 M NaCl solution using electrochemical impedance spectroscopy (EIS) tests. The EIS results indicated the successful release of encapsulated cerium nitrate from PUF microcapsules once the damage occurred in the epoxy coating, which led to effective self-healing of the epoxy-based coating. The presence of chlorine and cerium ions in the solution led to the precipitation of cerium hydroxides and oxides in the scratched area as a passive layer which hindered the corrosion in the damaged area. In addition, the EIS results showed that the healing performance of the coatings depends on the weight percent of microcapsules and the concentration of the self-healing agent. The highest self-healing performance was achieved for the maximum amount of microcapsule incorporation (10 wt %), while the increase in the microcapsule percent led to a decrease in the adhesion of the coating to the substrate.

Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

“…The EIS measurements were conducted to evaluate the anticorrosion properties of the coatings containing modified and unmodified TiO 2 with respect to the control sample [52] , [53] . Prior to the electrochemical assessment, the samples were scratched and then soaked with a 3.5 wt% NaCl aqueous solution for 18 days to reach a stable open circuit potential.…”

Corrosion Barrier Coatings: Progress and Perspectives of the Chemical Route

“…The addition of compounds such as Ce(NO 3 )6H 2 O and CeO 2 fine powder was also evaluated in the silane chemistry [95,96]. These enhancers, as one calls them in silane sol-gel chemistry, significantly improve the barrier property of sol-gel coatings combined with the anticorrosion properties of cerium ions [97][98][99][100][101][102][103][104][105]. The anticorrosion action of the cerium ions occurs via the passivation of the imperfections or cracks.…”

Optimization of microencapsulation of polyaspartic acid ester into UV curable epoxy‐acrylate resin using Taguchi method of experimental design

“…Numerous polymer materials are appropriate for creating the shell of the capsules. The most popular shells for microcapsules formation are poly(urea formaldehyde), [12][13][14][15][16][17] poly(melamine formaldehyde), [18][19][20] poly(urea melamine formaldehyde), 19,21 polyurethane, 22 polyurea, [23][24][25] poly(methyl methacrylate), [26][27][28][29] and others.…”

“…15 It was determined, however, that the reaction between the amino groups of PAAE and hydroxyl groups of the melamine-formaldehyde prepolymer occurred during the shell formation leading to reduced size of microcapsules. 16 It was reported that smaller microcapsules were less likely to rupture during the scratch process providing worse self-healing properties to the coating. 15 The successful microencapsulation process depends on numerous controlled and uncontrolled parameters within the preparation process, which are interconnected in a synergistic manner.…”

“…PAAE was encapsulated in poly(melamine‐formaldehyde) shell via in situ polymerization method 15 . It was determined, however, that the reaction between the amino groups of PAAE and hydroxyl groups of the melamine‐formaldehyde prepolymer occurred during the shell formation leading to reduced size of microcapsules 16 . It was reported that smaller microcapsules were less likely to rupture during the scratch process providing worse self‐healing properties to the coating 15…”