Silicone protective materials with controlled self-healing and toughness properties

Silicone elastomers with adjustable self-healing and mechanical properties have been prepared by the step-by-step synthesis procedure that 4,4′-methylenebis-(cyclohexyl isocyanate) (HMDI) and isophthalaldehyde (IPAL) sequentially cross-linked with aminopropyl terminated polydimethylsiloxane (AP-PDMS).

The characteristic imine and urea groups that related to self-healing ability and toughness have been detected in the silicone elastomers. The tensile stress of elastomers increases from ∼3 KPa to ∼1.0 MPa as increasing the ratio of urea to imine groups (0.35–3.3), while the elongation at the break still keeps in the range of 700−800 %. It was verified that the hydrogen bonding network exists in the self-healing polymers, which is responsible for its enhanced mechanical properties.

The dynamic interaction of imine groups decreases with the increase of urea groups due to the limited movement of the polymer chain by hydrogen bonds, resulting in the degeneration of self-healing properties.

Outstanding protective ability

Expectedly, the self-healing polymer (PDMS-UI-2) exhibits outstanding protective ability against corrosion of carbon steel in 3.5 % NaCl solution, owing to its rapid self-repairing property. Therefore, the study provides a facile and effective method to fabricate self-healing silicone materials with adjustable self-repairing capability and mechanical property, which can be potentially used as protective coatings in the marine environment.

The study can be found in Progress in Organic Coatings, Volume 140, March 2020.