A novel isocyanate-free strategy towards preparation of polyurea by a ring-opening reaction

Abstract

Due to serious concerns of isocyanate exposure on the health and safety of operators, isocyanate-free synthetic routes to obtain polyurea (PUA) are gaining more attentions. However, eco-friendly methods with convenient processing are scarce. Herein, a novel and facile method to prepare PUA with excellent physicochemical properties is provided. First, a PUA oligomer was prepared by a direct ring-opening reaction of N,N′-(methylenedi-p-phenylene)bis(aziridine-1-carboxamide) with a primary diamine. PUA materials were acquired under more convenient conditions compared with spraying application (i.e., solvent evaporation), hot pressing or casting. Studies on the physicochemical properties of PUA films showed that the new type of PUA exhibited stable chemical properties, good thermodynamic stability and good tensile properties (elongation at break: 144%; tensile strength: 56.4 MPa). This eco-friendly method avoids the use of isocyanate-containing derivatives but also gives more options to process PUAs. Our method is expected to have a wide range of applications in building, military, water conservation and transportation fields.