Covalent co-crosslinking of guanidine urea and phosphoramidate motifs enables creep-resistant, recyclable and flame-retardant thermosetting polyurea

Covalent adaptive networks generally suffer from insufficient creep resistance, mechanical strength, and flame retardancy. In this work, a dense GPAPUA dynamic crosslinking network was designed and synthesized through a one pot co-crosslinking strategy, integrating guanidine urea and phosphoramide motifs. Its synergistic covalent co-crosslinking design endowed the network with excellent creep resistance, reprocessability, and flame retardancy. Compared to commercial polyaspartic polyurea, GPAPUA exhibits 1.7-fold higher tensile strength and 2.3-fold greater modulus. The initial creep temperature increases from 40 °C to 80 °C, while the limiting oxygen index (LOI) rises from 25.1 % to 31.6 %, achieving UL-94 V-0 rating. Complete reprocessing is attained after hot-pressing at 180 °C for 1 h under a pressure of 10 MPa. This work establishes a straightforward and efficient approach to fabricating dimensionally stable, recyclable, and fire-resistant thermosets, showcasing promise as a sustainable alternative to commercial ployaspartic polyurea. • A dense CAN by co-crosslinking guanidine urea and phosphoramide motifs via a one pot method is constructed. • The initial creep temperature of the resin is increased to 80 °C, and the dimensional stability is enhanced. • The resin exhibits an intrinsic flame-retardant effect of UL-94 V-0 rating and an LOI value of 31.6 %. • The dynamic guanidine urea bond endows the resin with network reconstruction by hot pressing at 180 °C and 10 MPa for 1 h.