UV light triggered self-healing of green epoxy coatings

Numerous studies have been carried out globally to develop polymer coatings that could protect the underlying metal substrates from corrosion. Among these approaches, self-healing bio-based epoxy coating plays a promising role in corrosion protection. In the present study, a dual container self-healing coating system was developed from bio-based epoxy resin, halloysite nanotubes and silica nanoparticles. The halloysite nanotubes (HNTs) were filled with bio-based epoxy resin by vacuum infiltration technique and the silica nanoparticles were modified with a UV initiator by simple mixing. Later the filled halloysite nanotubes and modified silica nanoparticles were mixed with pure bio-based epoxy resin and hardener and cured to obtain self-healing composites. During the scratch/damage of the epoxy coating, the halloysite nanotube ruptures and the bio-based epoxy resin stored inside the nanotube fills the scratch and comes in contact with UV initiator immobilised on the silica nanoparticles, initiating the curing reaction. At 40 wt% of encapsulated HNTs, the scratch on the bio-based epoxy surface is found to undergo complete self-healing in the presence of sunlight. Overall, the composites showed an increased UV-shielding ability, improved thermal stability, and good transparency. Therefore, the developed bio-based epoxy composite is a viable self-healing coating for metals.