Flame retarded polyurethane vitrimers containing isocyanurate rings: Synthesis and properties

In this study, flame retarded polyurethane vitrimers, namely vitrimeric poly(isocyanurate urethane)s (VPICUs), were synthesized successfully by melting polycondensation simply from tris(2-hydroxyethyl)isocyanurate and dicarbamates. By increasing the methylene number in dicarbamates from 4 to 10, the VPICUs exhibit superior mechanical performance with elongation at break increases from 20% to 350% while the tensile strength decreases from 80 to 32 MPa, and the toughness can be significantly enhanced from 9 to 90 J/cm 3 . With a mass fraction of isocyanurate ring at 26.6%, for VPICU10-2.5/2, the flame retardancy is found to be the most excellent, with a UL-94 rating at V-0 and a LOI value at 25.9%. VPICU10 samples exhibit substantial relaxation behavior at higher temperature, and the network rearrangement activated by transesterification and transurethanization reactions offers the reprocessability without losing the properties. This work provides new insights into the construction of sustainable and high-performance flame retarded polymer materials.