Aiming at durable flame retardancy, smoke suppression, and qualified mechanical properties of polyurea by using surface-treated aluminum hypophosphite and interface-regulated MXene

This research outlines a strategy to improve both the flame retardancy and water resistance of polyurea (PUA) while largely preserving its mechanical integrity. Aluminum hypophosphite (AHP) was coated by triphenyl phosphate (TPP), and the resultant TPP@AHP exhibited improved compatibility and hydrophobicity. Additionally, ZIF-8@MXene, a nanohybrid material combining a metal-organic framework with MXene (Ti 3 C 2 T x ) sheets, served as both a reinforcing filler and a synergistic flame retardant. The use of 17 wt% TPP@AHP and 1 wt% ZIF-8@MXene in PUA enabled the composite to achieve a UL-94 V-0 rating and to maintain a limiting oxygen index (LOI) of 26.9% even after 7 days of water immersion. Cone calorimetry tests demonstrated that this formulation significantly reduced the peak heat release rate by 70.9%, total heat release by 30.8%, and smoke production by 32.1%. This work provided a feasible solution for preparing PUA composites with durable flame retardancy and qualified mechanical properties.