Abstract
Siliceous materials have been manifested as efficient synergists in the benign design of halogen-free flame retardant coatings via the formed dense and robust residue with a ceramic-like structure. Thus a novel ammonium polyphosphate (APP)/expandable graphite (EG)/TiO2 blended silica fume-based geopolymer coating is fabricated to explore an effective approach for high-value utilization of metallurgical solid wastes, and the synergistic flame-retarding effect is elaborated based on microstructure techniques and pyrolysis kinetic. An appropriate APP (2 wt%) facilitates the enhanced flame retardancy of the composite coating, evidenced by the reduced fire growth index (drops from 0.50 to 0.30 kW·m−2·s−1) and total smoke production (decreases from 903 to 479 m2), as well as the flame retardancy index climbs from 1 to 2.71. The doped-APP reacts with TiO2 and transforms into TiP2O7 during firing, leading to an increase in the Eα (climbs from 175.3 to 222.0 kJ·mol−1) at 1000–714 °C, according to the three-level chemical reaction model (F3). Finally, the synergistic flame-retarding effect involved in the APP/EG/TiO2 blended silica fume-based geopolymer coating contains the endothermic expansion of EG at 200–500 °C, degradation of APP at 300–500 °C, dehydration of polyphosphoric acid at 500–700 °C, and the decomposition of phosphates above 700 °C, respectively.
Published Version
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