Dimensional change of red phosphorus into nanosheets by metal–organic frameworks with enhanced dispersion in flame retardant polyurea composites

Red phosphorus (RP) is a promising polymeric flame retardant due to its abundance of flame-retardant elements. Unfortunately, the irregular size of RP leads to poor dispersion in polymer matrices, which greatly limits its wide application in flame-retardant polymer materials. Here, RP is transformed into a two-dimensional (2D) lamellar structure by a simple green method, while ZIF-67 nanoparticles are grown in situ and uniformly embedded in them. The 2D porous RP@ZIF (2D RP@ZIF) composites exhibit excellent flame-retardant properties and mechanical properties in polyurea (PUA) matrix. The peak heat release rate, total heat release, the peak of smoke production rate and total smoke production of PUA composites added with 5 wt% 2D RP@ZIF decreased by 48.0 %, 54.2 %, 20.4 % and 22.2 %, respectively. Due to its well compatibility, the elongation at break and tensile strength of PUA composites were 308.02 % and 9.21 N in the mechanical test, respectively. Compared with previous work, this is the first time that a 2D RP hybrid flame retardant has been prepared by metal organic framework and applied to flame retardant PUA.