Epoxy-based smart coating with self-repairing polyurea-formaldehyde microcapsules
For the study, self-reparable microcapsules which can repair microcracks in the coating matrix and effectively inhibit the corrosion at the substrate/coating interface during service have been evaluated. The main objective was to fabricate an innovative pH-responsive permeability-switching polyurea-formaldehyde (PUF)-based microcapsule laden with 8-hydroxyquinoline (8-HQ) as the core material for the production of smart epoxy coating for the long-term protection of Al alloys.
Self-repairing action occurs via two mechanisms
The results indicate that the self-repairing action occurs via two mechanisms: firstly, by the initiation of chain mobility at the modified coating defects on heat treatment. Secondly, by the crosslinking of the swelled hydrogel present in the PUF shell wall via the various polymer–polymer interactions. The active corrosion protection was due to the (smart) pH response–release ability of the encapsulated inhibitor (8-HQ) with an increase in corrosion degree. Meanwhile, the even dispersal of the fabricated microcapsule with its intrinsic rough surface in the epoxy coating matrix contributed to the improved barrier and adhesive properties.
The study has been published in Journal of Coatings Technology and Research volume 17 (2020).