Flame retardant polyurethane microbubble elastomer based on ionic liquid/ammonium polyphosphate/aluminum hypophosphite ternary flame retardant system

To develop a highly efficient flame retardant system for polyurethane microbubble elastomer (PME), a phosphate-based ionic liquid (IL) 1-methyl-3-(dioxyphosphoryl)-propyl imidazole bromide was synthesized, and then combined with ammonium polyphosphate (APP) and aluminum hypophosphate (ALHP) to form a ternary flame retardant system, which shows excellent synergistic flame retardancy and plays an important role in both gas phase and condensed phase flame retardancy. Compared with pure PME, the limiting oxygen index of flame retardant PME with 6 wt% IL and 15 wt% APP/ALHP increased from 20.25% to 29.25%, the char yields is increased by 13 times, and the heat release rate, total heat release rate, mass loss rate, and smoke production rate are reduced by 74%, 19%, 67%, and 22%, respectively. Ignition time increased from 9 s to 19 s, and extinguishing time increased from 295 s to 573 s. At the same time, the addition of IL promoted the dispersion and compatibility of APP/ALHP in the PME matrix and improved the mechanical properties. In addition, IL also shows potential in antistatic modification, providing the possibility for materials to meet both flame retardant and antistatic requirements.