Preparation of self-healing epoxy resin coatings based on dynamic disulfide bonds

Abstract

Defects and mechanical damage that lead to peeling, corrosion and other potential hazards during practical applications are inevitable in epoxy coatings due to the high cross-link density of the epoxy network. Herein, the authors synthesized a self-healing polythiourethane (SPTU) material containing dynamic disulfide bonds for the design and preparation of an SPTU–epoxy coating. Fourier transform infrared spectroscopy, proton (1H) nuclear magnetic resonance spectroscopy and scanning electron microscopy showed that 2-hydroxyethyl disulfide was successfully introduced into the polythiourethane system. Due to the fracture and reattachment of double sulfur bonds, the 3% SPTU–epoxy coating exhibited good self-healing properties in scratch treatment, the scratch being repaired completely after 2 h at 85°C. Meanwhile, 75.7% of the tensile performance of the completely fractured 3% SPTU–epoxy sample was retained after self-healing. The Tafel polarization curve and electrochemical impedance spectroscopy results showed that the 3% SPTU–epoxy coating had excellent corrosion resistance and still provided considerable corrosion resistance after 19 days of immersion corrosion tests. The self-healing coating exhibited good self-healing ability under heating conditions, which is attributed to the bond breaking and reconnection of dynamic bonds provided by the self-healing component. The self-healing properties and corrosion resistance of the prepared coating effectively improve the service life of the epoxy coating and provide some guidance for corrosion protection of epoxy coatings.