Optimization of smart self-healing coatings based on micro/nanocapsules in heavy metals emission inhibition

Polymer coating systems are classically an overcoat on previous coatings to provide a dense barrier against pollution (heavy metals) emission to the environment. Self-healing coatings are considered as an alternative route for efficient protection. Such coatings typically incorporate micro/nanocapsules that contain film-formers; which polymerize in the presence of air and heal the crack even at the zones that recognition and manual intervention is hard and costly or impossible. In this study, micro/nanocapsules with urea–formaldehyde as a shell and drying oil as a core were synthesized by in situ polymerization and the characteristics of these capsules were studied by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The final results of the coatings were obtained from electrochemical impedance spectroscopy (EIS) and polarization tests were compared with witness coating without a capsule. The results show their performance is suitable. Moreover, three coatings with synthesized capsules for three different agitation rates with the same thickness were compared for obtaining optimum rate. In the optimum rate, the thickness was optimized. The effect of the addition of micro/nanocapsules on mechanical properties of coatings was investigated with pull-off and cupping tests.

► The effective parameters in synthesis of micro/nanocapsules were investigated.
► The advantages/disadvantages of embedding the capsules in coatings were studied.
► A comparative study by electrochemical and mechanical tests were done on coatings.
► The simultaneous effects of agitation rate and thickness reduction were optimized.
► This new technology improves protective ability, safety and service life of apparatuses.