Synthesis of ZnFe2O4@Mg-Al-SDBS LDH composites for regulating heat and fire safety properties of polyurea

The flame retardant zinc ferrite@Mg-Al-sodium dodecyl benzene sulfonate layered double hydroxide (ZnFe 2 O 4 @Mg-Al-SDBS LDH) was prepared successfully by simple hydrothermal method and co-precipitation method. ZnFe 2 O 4 nanoparticle was used as the core on which Mg-Al LDH was encapsulated to form a spherical structure with a lamellar intercalation layer. The microstructure, the phase structure, and the thermal properties of flame retardant were characterized in detail. Compared with pure polyurea (PUA), the total heat release (THR), peak heat release rate (PHRR) and smoke factor (SF) of PUA/ZnFe 2 O 4 @Mg-Al-SDBS LDH 3.0 wt% decreased by 17.64%, 20.13%, and 28.42%, respectively. In the combustion process, Mg-Al LDH could generate porous metal oxides (Al 2 O 3 and MgO), and ZnFe 2 O 4 could also be decomposed into ZnO and Fe 2 O 3 . These oxides catalyzed cross-linking of polymer molecules, to promote the formation of a dense char layer, and isolated heat and combustible gases from the underlying material. The improved flame retardant properties of the modified intercalated microspheres could be attributed to catalytic carbonization and physical barrier. Moreover, the mechanical properties of PUA composites were tested by universal tensile testing machine. The results showed that the addition of ZF@MASL flame retardant had little influence on the mechanical properties of PUA composites.