Surface modified alginate multicore microcapsules and their application in self-healing epoxy coatings for metallic protection

Abstract

Conventionally, self-healing microcapsules are synthesized from synthetic polymers associated with complicated fabrication process. It appears in the range of (10–400 μm) to suit different applications. Here, we report green self-healing microcapsules synthesized from alginate biopolymer. The synthesis process is straightforward, require no pH and temperature change. Using simple methods (electrospraying and air atomization), alginate/epoxy microcapsules of two size range (∼350 μm and ∼150 μm) are fabricated. However, the smaller air atomized microcapsules collapsed after drying. Chitosan coating successfully provides structural support to small air atomized microcapsules and improves the elastic modulus of both microcapsules. Peak force quantitative nanomechanical mapping (PFQNM) under atomic force microscopy (AFM) is used to acquire the capsules elastic modulus. Chitosan coating slightly improved the elastic modulus of electrosprayed microcapsules from 3.43 ± 0.80 GPa to 4.45 ± 0.80 GPa. Although HNTs are unable to enhance the structural integrity of small microcapsules, it improves the elastic modulus of big microcapsules up to 6.04 ± 0.20 GPa. To evaluate the self-healing ability, these microcapsules and Scandium (III) triflate catalyst are incorporated into epoxy coating and applied on a metallic substrate. The capsule-catalyst self-healing coatings showed good self-healing performance in closing the gaps on the scratch.