Preparation And Properties Of Self-healing Crosslinked Non-Isocyanate Polyurethane Based On Diels-Alder Reaction

At present,research on DA self-repairing polyurethanes has focused on conventional polyurethanes based on furan rings and bistaleimides.Because the traditional polyurethane synthesis process requires the use of highly toxic reagents such as polyisocyanates,and the preparation of polyisocyanates also requires the participation of toxic phosgene,contrary to the concept of green and environmental protection.Therefore,in this thesis,the non-isocyanate method was used to prepare difunctional D-NIPUs and trifunctional T-NIPUs by polyaddition reaction using bicyclic carbonate.Then,a low molecular weight and high C=C content unsaturated polyester was prepared by bulk polycondensation,and a self-repairing non-isocyanate polyurethane SD-NIPUs was prepared by DA reaction with D-NIPUs.Due to the high C=C content in the unsaturated polyester,the SD-NIPUs have excellent self-healing properties,and the initial self-repairing efficiency can reach 100%.At 120?,the surface crack can be repaired in 5 minutes.And because of the good flexibility of the unsaturated polyester,SD-NIPUs also have excellent elastic recovery ability,and the elastic recovery performance of SD-NIPU-1 can reach 92%.ST-NIPUs prepared by using T-NIPUs and a bismaleimide prepared by maleic anhydride and 2-methylpentanediamine through dehydration cyclization of acetic anhydride.ST-NIPUs have excellent mechanical properties due to the rigidity of cyclic imide groups.ST-NIPU-4 has an initial tensile strength of 21.10 MPa.It also has good self-healing properties.At 140?,the crack can be repaired in 20 minutes.The initial self-repairing efficiency of ST-NIPU-5 can reach 80%.