In-situ polymerized zinc phytate chelated Si-C-P geopolymer hybrid coating constructed by incorporating chitosan oligosaccharide and DOPO for flame-retardant plywood

Zinc phytate (ZnPA) chelated geopolymer and in-situ polymerized chitosan oligosaccharide (COS)/DOPO explored a challenging and exciting flame retardant organic–inorganic hybrid coating via sol–gel method to find halogenated high-efficiency bio-flame retardants are widely used as decorative materials for flame-retardant plywood. Herein, the results show that the appropriated ZnPA (0.5 wt%) enhances the flame retardancy of the geopolymer coating, the peak of heat release rate (p-HRR) decreases from 136.09 to 99.39 kW·m−2, the fire growth index (FGI) dropped from 0.47 to 0.28 kW m−2 s−1, the fire performance index (FPI) climbs from 1.00 to 2.52 s·m2·kW−1, and the flame retardancy index (FRI) climbs from 1.00 to 2.52. Meanwhile, through the microstructural analysis of the residual layer, a strong, compact and non-flammable resilient residues is obtained after combustion; Moreover, the pyrolysis kinetics show that the Z.-L.-T. three-dimensional diffusion reaction model governs the pyrolysis of hybrid coatings. Appropriated ZnPA increases the pyrolysis Eα from 138.95 kJ·mol−1 to 160.75 kJ·mol−1 at 741 ∼ 890 ℃ and improves the thermal stability of the coating. The Si-C-P structure improves the formaldehyde adsorption rate by 46.5%. Therefore, this study, by preparing COS-pretreated ZnPA and DOPO to co-construct alkali-excited cenospheres-based Si-C-P coating, reveals the sustainable development of modified bio-based geopolymer flame-retardant coatings in the construction industry.