| Summary: | An ecological ammonium thiocyanate (NH<sub>4</sub>SCN)-modified geopolymeric coating was facilely prepared for flame-retarding plywood. The effect of NH<sub>4</sub>SCN on the flame resistance was preliminarily investigated using cone calorimeter (CC), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermal gravimetry (TG). The results show that 1 wt.% NH<sub>4</sub>SCN as dopant is of paramount importance to generate a compact and continuous coating. The formation of a smooth, intact, and uniform-swelling siliceous layer during combustion facilitates enhanced fire resistance, evidenced by the increased fire performance index (FPI), reduced fire growth index (FGI), and 39.7% decreased value of peak heat release rate (pHRR), in comparison to those of the sample without NH<sub>4</sub>SCN. Because of the reducibility of O<sub>2</sub>-consuming NH<sub>4</sub>SCN, the compact shielding-layer containing carbonate and sulfate, as well as the release of NH<sub>3</sub>, the NH<sub>4</sub>SCN-modified geopolymeric coating exerts an enhancement on the flame-retardant efficiency.
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