Novel halogen‐free Si‐C‐P flame‐retarding coatings constructed by DOPO/flake graphite co‐doping silica fume‐based geopolymer

Abstract

AbstractA facile design for value‐added recycling of metallurgical solid waste is urgent for developing safe and sustainable human settlements. Therefore, novel DOPO/flake graphite (FG) co‐doped silica fume‐based geopolymer coatings for flame‐retarding plywood were prepared to seek a halogen‐free and low‐carbon Si‐C‐P fireproof method. The results show that appropriate DOPO (1 wt%) constitutes an enhanced flame retardancy, evidenced by the reduced peak of heat release rate (decreases from 153.48 to 96.94 kW m−2) and the rising flame retardancy index (climbs from 1.00 to 2.32). Meanwhile, its pyrolysis is identified as the three‐level chemical reaction model (F3), the hydrogen bond crosslinking between the POC and HOSiO results in a rising Eα at 1000–731°C (increases from 163.60 to 198.83 kJ mol−1). Finally, the synergistically flame‐retardant mechanism consists of water volatilization at 100°C, the as‐formed porous carbonaceous layer at about 200°C, transformations of DOPO at 300–500°C, the formed DOPO derivatives at 500–700°C, and the decomposition of DOPO derivatives (condensed phase barrier) above 700°C, respectively. The yielded residues generate a 56% formaldehyde adsorption rate. It proposes a halogen‐free and low‐carbon strategy for designing Si‐C‐P hybrid flame‐retarding coatings, indicating an ecological direction for the value‐added utilization of metallurgical solid waste.