Green Flame Retardancy: Biomass-Based Treatment for Poplar Wood

Poplar wood ( Populus alba L.) was modified using a fully bio-based treatment that combined furfuryl alcohol (FA) and ammonium phytate (AMP), catalysed by phosphoric acid. The in-situ polymerization created a cross-linked poly(furfuryl alcohol) matrix that effectively immobilized AMP within the wood structure. The treatment increased weight percent gain to 21.7% and density from 0.394 to 0.499 g cm⁻³. FTIR and SEM confirmed the uniform incorporation of FA and AMP in both cell walls and lumina. The modified wood showed a limiting oxygen index of 28% compared to 18% for untreated wood, produced up to 35.7% char at 800°C, and self-extinguished rapidly during flame exposure. Fire tests demonstrated substantial reductions in total heat release, carbon monoxide, and smoke production, along with a six-fold increase in residual mass. Water uptake decreased by 38%, while Shore D and Janka hardness increased by 12% and 18%, respectively. Importantly, leaching resistance exceeded 91%, confirming durable fixation of the flame-retardant system. These synergistic improvements in fire safety, moisture resistance, and mechanical properties highlight a sustainable approach for producing high-performance, flame-retardant lignocellulosic materials from low-value poplar.