Pyrolysis Kinetics and Reaction Mechanism of Magnesium Fireproof Board Based on TG-FTIR Analysis

Abstract Magnesium fireproof boards have emerged as a versatile and sustainable construction material, offering a viable alternative to traditional fiber cement and gypsum boards. However, the detailed pyrolysis mechanisms and kinetics remain insufficiently understood, limiting the design of materials with optimized fire-resistant performance. By using thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR) coupling technology combined with the Flynn-Wall-Ozawa (FWO)/Starink and Coats-Redfern (CR) method, the pyrolysis characteristics, reaction mechanisms, and volatile emissions of the magnesium fireproof board were systematically analyzed. The study revealed four pyrolysis stages: water removal, magnesium chloride decomposition, carbonate decomposition, and the formation of stable MgO. Through kinetic analysis, the activation energies for each stage were calculated as 83.73 kJ / mol (Stage I), 178.12 kJ / mol (Stage II), 204.34 kJ / mol (Stage III), and 286.47 kJ / mol (Stage IV), respectively. The most probable reaction mechanism was g ( α ) = [ ( 1 – α ) − 2 − 1 ] / 2 , g ( α ) = [ ( 1 – α ) − 2 − 1 ] / 2 , g ( α ) = ( 1 – α ) − 1 − 1 , and g ( α ) = 1 – ( 1 – α ) 1 / 2 . FTIR analysis identified volatile decomposition products, including dehydration, magnesium chloride decomposition, and carbonate breakdown. These processes were dominated by the decomposition of magnesium chloroxylate crystals and carbonates, yielding products such as magnesium oxide and carbon dioxide. The findings provide a mechanistic understanding of magnesium fireproof board decomposition and stability under high-temperature conditions, thereby supporting the design of materials with enhanced thermal and fire-resistant properties for advanced construction applications.