Designing Smart Microcapsules with Natural Polyelectrolytes to Improve Self-Healing Performance for Water-Based Polyurethane Coatings

Abstract

Active anticorrosive organic coatings adopting microcapsules (MCs) have lately attracted extensive attention as they were proven to be effective to minimize metal corrosions and offer a long-lasting protection performance. Herein, a novel environmental-friendly active corrosion protection system was designed for aluminum alloy 2024 (AA2024) based on water-based polyurethane coatings with the addition of water and alkaline pHresponsive smart MCs, which is fabricated by utilizing 2mercaptobenzothiazole (2-MBT) as an inhibitor, halloysite clay nanotubes (HNTs) as an inhibitor carrier, and the natural polyelectrolytes ε-poly-L-lysine (ε-PLL) and sodium alginate (SA) as layer-by-layer (LBL) encapsulation polyelectrolytes. Salt spray tests and electrochemical measurements prove that the scratched coatings with embedded MCs possess an excellent self-healing performance by forming an adsorption layer of released 2-MBT on the AA2024 surface, thereby providing over 90% inhibition efficiency within 6 days' immersion. The UV−vis spectrophotometer results further showed that the release of 2-MBT is a three-stage long-term process sensitive to water and alkaline pH value, while the outward release rate is both regulated by the solubility of 2-MBT and the SA layer. The fabricated MCs not only offer a great promise to provide an excellent self-healing performance but also shed light on the future design of advanced MCs on demand based on the LBL technique.

Dual-Shell Microcapsules for High-Response Efficiency Self-Healing of Multi-Scale Damage in Waterborne Polymer–Cement Coatings

“…So, these current microcapsules directly lose crack ability if they are present in a coating. Microcapsules with weaker structural strength may be damaged during the storage and stirring of the coating, which can effectively trigger the self-healing performance under low stress [ 8 , 18 ]. Therefore, it is of great interest to develop self-healing microcapsules with thin walls.…”

One-step preparation of hydrophilic–hydrophobic asymmetric bilayer microcapsules via photopolymerization

“…These diverse applications require the shell structure to remain robust and provide good encapsulation for the core material, as well as being uniformly dispersed in the medium. [4][5][6] For microcapsules used in water-based systems, such as artificial cell models 7 and water-based smart coatings, 8,9 it is essential to balance the hydrophilicity and water-resistance properties of microcapsules. On the one hand, it is necessary to realize the uniform dispersion of the microcapsules in water, which puts high demands on its surface hydrophilicity; on the other hand, microcapsules must remain stable during storage and usage to avoid premature release of the core material, which necessitates water-resistance of the shell.…”