Designing fire-resistant oriented strand board via B-N-Al synergy: multicomponent interfacial regulation and the formation of a unified ceramic-char barrier

Abstract

Facing the global shortage of forest resources, oriented strand board (OSB) has attracted increasing attention for its efficient use of small-diameter timber and wood-processing residues. However, its inherent flammability and the deterioration of mechanical properties induced by conventional flame retardants remain critical challenges. In this study, a low-dosage borax (BX)-melamine cyanurate (MCA)-nano-alumina (Al₂O₃) synergistic compatibilization strategy was proposed to simultaneously enhance the fire safety and mechanical performance of OSB. The designed system forms a robust “ceramic–carbon composite expanded protective layer” during combustion, effectively suppressing heat transfer and thermal decomposition. Compared with neat OSB, the residual char yield increased by 78%, while the peak heat release rate, total heat release, total smoke production, and peak smoke production were reduced by 15%, 32%, 69%, and 89%, respectively. Meanwhile, BX-mediated interfacial bonding enabled strong chemical interactions among flame retardants, Wood shavings (WS), and 4,4′-methylenediphenyl diisocyanate (MDI), improving interfacial compatibility. As a result, both longitudinal and transverse bending strength and modulus of OSB were well maintained at high levels. This work provides a novel and practical route for developing high-performance flame-retardant OSB, which not only enables the high-value utilization of wood but also significantly advances the engineering applications of OSB in advanced technology fields.