Multifunctional hydrogel-modified laminated wood for high-strength and fire-resistant structural applications

Wood-based structural materials possess inherent deficiencies in flame retardancy and mechanical resilience, which limit their applicability in load-bearing scenarios and environments with elevated fire risk. In this study, we present a high-performance laminated wood composite fabricated by integrating delignified wood veneers with a multifunctional hydrogel interlayer composed of sodium alginate, phthalate-modified kaolinite, and ammonium polyphosphate. The delignified wood scaffold exhibits a porous, cellulose-rich structure that facilitates uniform and deep hydrogel infiltration, while simultaneously promoting strong interfacial adhesion through extensive hydrogen bonding. As a result, the composite achieves a tensile strength of 913 MPa and a specific strength surpassing 2700 MPa·cm 3 ·g −1 . The hydrogel matrix, stabilized through hierarchical ionic coordination, enhances the composite's structural integrity, dimensional stability, and thermal resistance. Under thermal stimulation, the system forms a compact, ceramic-rich char layer and emits non-flammable gases (NH 3 , H 2 O, CO 2 ), establishing a dual-phase flame-retardant mechanism that combines condensed-phase thermal insulation with gas-phase radical suppression. Cone calorimetry measurements reveal a 71.9 % reduction in peak heat release rate and a limiting oxygen index of 42.2 %. The proposed strategy provides a sustainable and scalable pathway for the development of bio-derived structural composites that integrate mechanical robustness with fire safety, thereby advancing their potential for environmentally responsible and high-performance engineering applications.