Synthesis of self-healing soybean oil-based waterborne polyurethane based on Diels–Alder reaction

In order to endow water-based polyurethane with special functionality, vegetable oil-based waterborne polyurethane with self-healing properties is synthesized. Firstly, soybean oil-based emulsifier (GA-ESO) was prepared by epoxy soybean oil and glutaric acid without solvent and catalyst. Then, two Diels−Alder (DA) diols were prepared by the DA reaction between N , N ′-(4,4′-methyldiphenyl) bismaleimide, 4-maleimide phenol and furfuryl alcohol, respectively. Finally, GA-ESO and DA diols used as the raw material was reacted with isophorone diisocyanate to synthesize a series of soybean oil-based waterborne polyurethane with self-healing behavior. The effects of DA diol on the properties of polyurethane films and the self-healing process and mechanism of polyurethane membrane were investigated. The results showed that after the addition of DA diol, the particle size of polyurethane emulsion increased from 28.8 to 85.3 nm, the tensile strength was improved from 0.3 to 12.6 MPa, and the water contact angle was enhanced from 68.5° to 84.2°. In addition, it can be observed that with the addition of DAdiol, the polyurethane film had self-healing behavior at high temperature, and the highest self-healing efficiency can reach 100%.