In-situ grown SiC whiskers enhance flame retardancy of alkali-activated gold tailings geopolymer composite coatings by incorporating expanded graphite

Abstract

Herein, a gold tailings-based flame-retardant coating blended with zinc phytate (ZnPA)/β-cyclodextrin (β-CD)/expanded graphite (EG) is prepared by the sol-gel method. The coating is used in flame-retardant plywood. It explores the efficient recycling of industrial solid waste. Firstly, the microstructure analysis reveals that EG forms in-situ SiC ceramic whiskers in the solid solution of orthosilicate and pyrophosphate. Meanwhile, the synergistic flame-retardant effect is explained through morphological characterization and pyrolysis kinetics analysis. Adding 2 wt% EG significantly improves the flame retardancy of the coating, as evidenced by a decrease in the peak of heat release rate (p-HRR) and an increase in the fire performance index (FPI). The p-HRR decreases from 104.67 kW·m−2 to 75.08 kW·m−2, while the FPI increases from 2.11 s·m2·kW−1 to 3.51 s·m2·kW−1. Moreover, the pyrolysis kinetics is modeled using the Zhuralev-Lesokin-Tempelman (Z.-L.-T.) three-dimensional diffusion-reaction model, revealing an increase in Eα from 74.90 to 85.82 kJ·mol−1 in the temperature range of 674–890 °C. The coating exhibits 60% formaldehyde adsorption performance. Therefore, this study proposes a new in-situ whisker synergistic flame-retardant system and sheds light on the potential applications of new geopolymers in the sustainable development of the green flame-retardant field.