Autonomous self-healing in epoxy coatings provided by high efficiency isophorone diisocyanate (IPDI) microcapsules for protection of carbon steel

Preparation and Characterization of Ethylenediamine-Polyurea Microcapsule Epoxy Self-Healing Coating

“…Generally, Impedance modulus (|Z|) at a frequency of 0.01/0.005 Hz is applied to evaluate the coating resistance. The |Z| 0.01Hz value of the alkyd varnish coatings AVC containing isophorone diisocyanate (IPDI) increased from 0.782 to 1.515 MΩ•cm 2 [22], indicating the barrier properties of modified coatings, and this figure for self-healing epoxy coatings presented by Attaei et al [29] showed a similar trend, rising from 1 GOhm•cm 2 to 10 GOhm•cm 2 after 35 days' immersion. Similarly, in this study, Figure 8b,d shows the Bode plots of scratched coatings with different microcapsule contents after immersion for 24 to 96 h. It can be seen that the impedance magnitude of M5 is much higher compared to that of M2 and M0 throughout the whole process.…”

“…During the process of microcapsules synthesis, the FTIR spectra of EDA-Polyurea microcapsules and control groups including the shell and pure EDA were measured with respect to the urea-bond functional groups by using Fourier transform infrared spectroscopy (Nicolet8700, Thermo Fisher Scientific, Waltham, MA, USA) in a wave number range of 500-4000 cm −1 [29,30].…”

“…The microcapsules were heated from 25 to 650 • C at a rate of 20 • C/min in a nitrogen atmosphere with a gas purge of 40 mL/min. The core content of the microcapsules was roughly calculated by the decreased peak of the weight loss curve [12,29,31].…”

“…EIS measurements (p4000A, Ametek Group Advanced Measurment Technology, Princeton, NJ, USA) have conventionally been used to evaluate the performance of self-healing coatings [22,29]. Before the EIS measurement, the Q235 steel samples (50 mm × 50 mm) were coated by a series of modified epoxy resins with different contents of synthesized microcapsules (0.0 wt%, 2.0 wt% and 5.0 wt%).…”

“…The previous research reported by Lang et al [12] showed that the encapsulated core percentage was in the range of 76 to 82 wt% for the microcapsules obtained under different stirring rates, and Ye et al [31] found that encapsulation ratio of poly (urea-formaldehyde) microcapsules was 90.42%. In addition, isophorone diisocyanate (IPDI) microcapsules prepared by Attaei et al [29] showed that the core content of epoxy ester was 76 wt%. Compared with these results, the main reason for the relatively low content of the core material in our experiment was that EDA was a volatile liquid, and a small amount of EDA was volatilized during the synthesis.…”