Functionalized Hexagonal Boron Nitride Significantly Improves the Flame Retardancy and Mechanical Strength of Wood Coatings

Abstract Hexagonal boron nitride (h‐BN) is a highly stable, thermally conductive, and chemically inert material. However, it has several drawbacks as a flame retardant, including limited flame‐retarding performance, poor dispersibility in polymer matrices, and adverse effects on the mechanical properties of composite materials. To address these issues, we propose a new method that combines physical dispersion with chemical functionalization of h‐BN, using which we successfully developed an h‐BN‐based flame‐retardant material, significantly enhancing the flame‐retardant and mechanical properties of wood. Specifically, 3,5‐diamino‐1,2,4‐triazole and sodium hexametaphosphate were used to create layered sandwich structures with h‐BN. The resulting h‐BN‐guanazole‐sodium hexametaphosphate (BNGS) composite was then mixed with a urea–formaldehyde (UF) resin to form a cross‐linked macromolecular flame‐retardant resin. Wood coated with a UF resin containing 2 wt.% BNGS has a limiting oxygen index of 33.80 % and passes the UL‐94 V‐0 test. Compared with those of untreated natural wood (NW), the heat release rate and total heat release of the resin‐coated wood decreased dramatically by 76.00 and 80.67%, respectively. Moreover, the coating increases the impact strength of the NW, which is originally 7.35 kJ/m 2 , to 13.10 kJ/m 2 . This work provides a simple and high‐performance solution for wood protection.