Self-healing epoxy with a fast and stable extrinsic healing system based on BF3–amine complex

Abstract

To avoid the high corrosiveness of the fast-healing epoxy system previously developed by our lab, which contains a strong Lewis acid or Brønsted acid, we introduced a much less corrosive BF₃–amine complex (50% boron trifluoride–2,4-dimethylaniline in 1,4-butanediol) as a replacement. The new hardener was successfully synthesized, encapsulated in silica hollow microcapsules, and embedded in an epoxy matrix with a microencapsulated cycloaliphatic epoxy monomer. Impact tests indicated that the healing system worked as expected. The self-healing epoxy composite can regain its strength within seconds at room temperature, and its self-healability remained stable after 4 months of storage. The high cationic polymerization reactivity of the cycloaliphatic epoxy accounts for the rapid restoration. It is believed that the present work represents an important step towards practical usage of the fast extrinsic self-healing strategy.