CO2 Induced Synthesis of Zn-Al Layered Double Hydroxide Nanostructures towards Efficiently Reducing Fire Hazards of Polymeric Materials

Improving the flame retardancy of polymeric materials is an imperative yet challenging task without deteriorating their intrinsic properties. Herein, we reported a facile approach to grow zinc-aluminum layered double hydroxide (Zn-Al LDH) nanostructures on the surfaces of polymer substrates in order to overcome their high fire hazards. CO2 induced growth of Zn-Al LDH allowed slow and homogeneous nucleation, leading to the as-synthesized Zn-Al LDH with ultra-large size (several microns) and perfect hexagonal shape. The Zn-Al LDH uniformly covered the surfaces of substrates and provided excellent flame-retardant effect. Cone calorimeter measurements revealed that the peak heat release rate of Zn−Al LDH-coated wood and rigid polyurethane foam (RPUF) were significantly decreased by 55% and 51%, respectively, compared to those of the pristine wood and RPUF; also, Zn−Al LDH-coated wood and RPUF showed notable reduction in total smoke production up to 47% and 28%, respectively. These findings demonstrate that CO2 induced synthesis of Zn-Al LDH nanostructures is a feasible and effective solution to polymeric materials with desirable flame-retardant and smoke-suppression properties.