Stiff UV-Curable self-healing coating based on double reversible networks containing diels-alder cross-linking and hydrogen bonds

A series of multi-crosslinkable, self-healing coatings were developed to enhance the mechanical properties through tandem UV-curing and Diels-Alder (DA) chemistry. First, multi-arm UV-cured polyurethane (PU) pre-polymers (IPxH 12 ) were prepared based on cyclotriphosphazene monomer (H 12 ) with more benzene ring structure and half-blocked photosensitive oligomer. Then N, N'-(4, 4′-methylenediphenyl) bismaleimide (BMI) and furfuryl alcohol (FA) were used as the raw materials to prepare DA intermediate by Diels-Alder reaction. The DA intermediate was further reacted with methacrylic acid isocyanate (IEM) to obtain the modified I DA monomer (UV curable DA monomer, containing acrylic double bond). The structure of IPxH 12 and I DA was characterized by FT-IR and 1 H-NMR. UV-cured self-healing coatings were prepared by designing some coating formulations with the IPxH 12 , I DA and initiator. The self-healing properties and mechanical properties of the coatings were investigated. The results revealed that the hardness of the coating was up to 3H, and the introduction of I DA improved its self-healing performance, when the ratio of DA monomer to PU was 2:1, the repair effect was the best. The UV-curable self-healing coating has potential application in metal protection and other fields.