Preparation of multifunctional flame retardant composite wood by doping poplar cell walls with metal phytates

Phytic acid as an efficient, green and renewable bio-based flame retardant. However, in view of the large number of toxic fumes generated during combustion and the easy loss of flame retardants, to tackle these issues, the current study employed a straightforward two-step process to generate phytate metal salt wood composites (PAN-M, M = Mg, Cu, Fe, Ai and Ni) in cell walls. Compared with natural wood (Control), PAN-M has good leaching resistance of 15 similar to 50%, lower hygroscopicity of 15 similar to 30% and improved mechanical strength. The total heat release and smoke emission of PAN-Cu are reduced by 34.54% and 83.05% respectively, the LOI of PAN-Cu is increased by 117%, the smoke density SDR is only 8.38 and the weight gain is 16.9%. This is mainly due to the apparent surface coke protection of metal phytates and catalytic graphitisation of solid residues by metal ions. The improved carbon layer plays an effective insulating role, limiting flue gas emissions, flame retardant loss and water contact. In addition, results show that PAN-Cu can significantly enhance the dehydration effect of carbon compared to other metal ions. Therefore, PAN-M is an efficient, green and sustainable flame retardant for wood.