Novel self-healing epoxy coatings
Scientists report on self-healing epoxy coatings containing microcapsules filled with different amine compounds.
The study evaluated the self-healing efficiency of an epoxy coating added with poly(urea-formaldehyde) microcapsules filled with triethylenetetramine (TETA), aminated poly(dimethylsiloxane) (PDMS-a), or a polyamide/polyamine compound (PA), by measurements of corrosion evolution (salt spray tests), scanning electron microscopy (SEM), electrochemical impedance (EIS), infrared (FTIR) and x-ray photoelectron (XPS) spectroscopies.
Better substrate protection
Salt spray tests showed that the coatings added with PDMS-a and PDMS-a/TETA had better substrate protection. It was also observed that the protective performance is influenced by the increase in the mass content of microcapsules and by the curing temperature. In general, the addition of 15 % of microcapsules, with curing at 60 °C, showed better protection effect.
EIS results showed that additives coated with PDMS-a and PDMS-a/ TETA present higher values of impedance modulus |Z| than the original coating without microcapsules, proving the partial self-healing of the system. It was found that some EIS measurements reached |Z| values close to the coating without failure, a consequence of the point release of PDMS-a, as observed in SEM images, which also confirm that the crack width was significantly reduced and part of crack planes relinked after 48 h. XPS spectra indicated that the polymer found in the region of the failure was PDMS-a.