Multifunctional Nonisocyanate Polyurethane with Closed-Loop Recyclability Derived from Fully Biomass Resources

Biobased nonisocyanate polyurethanes (NIPUs) have been widely used as a substitute for petrochemical polyurethane in recent years because of their green and environmental protection. However, most studies focus on plant oil-based NIPUs, whose performance is limited, and their use is affected. In this work, rosin-derived cyclic carbonate (APAC) containing a rigid hydrogenated phenanthrene ring was used to prepare a fully biobased NIPU by the reaction of a biobased 1074 amine. Meanwhile, phosphorus-containing lignin derivatives were introduced as cross-linking agents to regulate the structure of the obtained NIPU so as to improve the strength and supplement the flame retardancy. With the introduction of rigid structures and the construction of a high cross-linking degree, the tensile strength of NIPUs can reach 16.5 MPa. The coordination between the phosphorus-containing group and the nitrogen-containing structure also gives NIPUs excellent flame-retardant properties, and the limiting oxygen index can be increased from 24.5% to 32%. Cone calorimetry and air combustion also verify the improvement of the flame-retardant performance of NIPU materials. In addition, due to the formation of dynamic carbamate bonds and dynamic imine bonds in the structure, NIPUs can achieve reprocessing and self-healing under mild conditions (60 °C), and the healing rate is more than 80%. Through structural evolution, the method used in this work to prepare NIPUs with rich advantages such as being flame retardant, of high strength, fully biobased, and recyclable shows great application potential.