Fabrication of eco-friendly and high-performance flame-retardant plywood based on nanocellulose/ferric citrate modified magnesium oxychloride cement

Conventional plywood currently suffers from formaldehyde emissions and the generation of smoke during fires. This study addressed these issues by preparing an eco-friendly, flame-retardant and smoke-suppressing plywood through the synergistic modification of magnesium oxychloride cement (MOC) with nanocellulose (CNCs) and ferric citrate (FC). Research indicates that the chemical coordination between citrate ions and Mg²+ in FC inhibits the growth of loose acicular crystals in Phase 5, inducing its transformation into a dense gel-like Phase 5. Concurrently, the microscopic bridging cracks provided by CNCs enhance dry and wet strength by 2-fold and 4-fold respectively, while improving Class II bond strength by 40.2%. In cone calorimeter tests, the synergistic action of FC and CNCs formed a dense microporous carbon layer on the char surface, reducing total heat release (THR), total smoke release (TSR), and average CO yield by 17.8%, 33.6%, and 60.5%, respectively. This study offers novel insights for developing environmentally friendly adhesives.