Dimensionally stable, flame-retardant, and leach-resistant furfurylated wood prepared by incorporating ammonium polyphosphate and nano-silica

Fast-growing plantation typically has some undesirable inherent qualities that restrict their use as engineering materials, such as dimensional instability, poor mechanical strength, and flammability (Sangregorio et al., Green Chem, 2020, 22, 2786-2798; Zhang et al., Fire Saf J, 2021, 121, 103297). In this study, a simple and environmentally friendly method was applied to improve low-quality poplar wood by building an organic-inorganic hybrid system with a combination of biomass-derived furfuryl alcohol (FA), ammonium polyphosphate (APP), and nano-silica (nano-SiO2). Different amounts of APP and nano-SiO2 were mixed with a FA water solution, impregnated into the poplar wood followed by curing at 103? to induce in situ polymerization of furfurylated wood (FW). The results showed that the FW/APP/SiO2 had strong self-extinguishing properties, and passed the UL-94 V-0 rating with a limiting oxygen index (LOI) value as high as 49.5%. Results from cone calorimetry and thermogravimetry suggested that APP and nano-SiO2 could have a synergistic effect, which successfully inhibited heat transfer and suppressed the smoke emission during its combustion by promoting char formation. Scanning electron microscopy shows that FA, APP, and nano-SiO2 can basically penetrate into the cell wall and modify the wood fundamentally. FW/APP/SiO2 also enhanced the phosphorus fixation in the wood and greatly reduced its leaching into water, indicating it has long-term fire resistance in service.