A novel ternary inorganic–organic hybrid flame retardant containing biomass and MOFs for high-performance rigid polyurethane foam

In this work, using biomass polydopamine (PDA) as an intermediate interface, ammonium polyphosphate (APP), PDA, and ZIF-67 were combined into a ternary inorganicorganic hybrid flame retardant (A@P-Z). Compared with the flame retardant system composed of a physical mixture of APP and ZIF-67, the hybrid flame retardant not only strengthened the mechanical properties of RPUF composites owing to its good compatibility but also emerged with low total heat release, low total smoke production, and low peak CO production rate in cone calorimetry tests. RPUF/A@P-Z passed the UL-94 V-0 rating, which presented high flame-retardant efficiency of inorganicorganic hybrid flame retardants and industrial application value of the composites. Due to the contribution of synergistic catalysis, the residual char of RPUF/A@P-Z showed high graphitization and high-quality char composition in a rich, rigid structure, which produced an outstanding charring effect and barrier effect. The hybrid flame retardant also produced an impressive flame inhibition effect in the gas phase, inhibiting the production of organic fragments and releasing phosphorus-containing and nitrogen-containing gaseous compounds with free radical quenching and diluting effects. This work provides a new and efficient way to prepare high-performance RPUF composites using inorganicorganic hybrid flame retardants.