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

An h-BN-based flame-retardant material is synthesized to improve the flame retardancy and mechanical properties of wood. Specifically, 3,5-diamino-1,2,4-triazole and sodium hexametaphosphate are used to create layered sandwich structures with h-BN. The resulting h-BN-guanazole-sodium hexametaphosphate (BNGS) composite is then mixed with a urea–formaldehyde (UF) resin to form a crosslinked macromolecular flame-retardant resin.

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/m², to 13.10 kJ/m². This work provides a simple and high-performance solution for wood protection.

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