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

Abstract

Waterborne polymer–cement coatings have been widely applied in building materials due to their organic solvent-free nature, low cost, and eco-friendliness. However, these coatings can easily crack during the drying process as a result of construction environment factors, compromising the barrier performance of the coating and limiting its large-scale application. In this study, a dual-shell self-healing microcapsule was developed, which can effectively heal damage on a macro scale in waterborne polymer–cement coatings. Specifically, this dual-shell self-healing microcapsule was designed with a silica gel shell and a tannic acid–cuprum (TA–Cu) double-shell structure embedded with an epoxy resin (EP) healing agent, which was successfully fabricated via a two-step in situ polymerization. This silica gel shell self-healing microcapsules can effectively load into waterborne polymer–cement coatings. As the coating dries and solidifies, the silica gel shell of the microcapsule also becomes loose and brittle due to dehydration. This improves the mechanical initiation efficiency of the microcapsules in the coating. This study provides a novel approach for the application of self-healing microcapsules in waterborne coating systems, which can significantly reduce cracking during the drying process of waterborne polymer–cement coatings and improve the service life of the coating under complex conditions.