Organophosphonic acid intercalation and surface-functionalized hydrotalcite-based flame retardant materials for epoxy resins with highly effective smoke suppression and fire safety

In this work, the green and efficient organic-inorganic hybrid flame retardant materials (PA-Si-PPO-LDHs) were prepared by introducing phenyl phosphoric acid (PPO) and phytic acid (PA) between layers and surface of hydrotalcites, and characterized. With the addition of 10 wt% PA-Si-PPO-LDHs, the EP composites achieved UL-94 V-1 rating and a limiting oxygen index of 30.0 %, and obtained 46.4 %, 37.0 % and 20.1 % reduction in heat release rate, CO production and total smoke production, respectively. In addition, the PA-Si-PPO-LDHs were better dispersed in EP, and the tensile, three-point bending and simple beam impact strengths of EP composites were improved in comparison with the pure EP. The prepared PA-Si-PPO-LDHs contributed to improve the flame retardant of EP composites by the formation of the dense char layer in the condensed phase, dilution of flammable gases and the released phosphorus-containing free radicals for capture of the H• and HO• free radicals in the gas phase. Co and Ni metal-catalyzed CO conversion of CO 2 reduced the release of heat and hazardous gases, and improve the fire safety of EP composites. The present work provided a simple method for the preparation of green and efficient LDHs-based organic-inorganic hybrid flame retardants for improving the fire safety of epoxy composites.