Study of thermal pyrolysis characteristics and fire extinguishing performance of novel halon alternatives for aviation applications

Brucite dry powder (BDP), as a novel alternative to aviation halon fire extinguishing agents, has garnered widespread attention. However, its development has been hindered by hygroscopicity due to its hydrophilic nature and a propensity for re-ignition caused by oil deposition. Consequently, this study employed perfluorodecyltrimethoxysilane (PFDTMS) to modify the surface of BDP, resulting in modified BDP (M-BDP) that exhibits both hydrophobic and oleophobic properties. The thermal stability and hydrophobicity of M-BDP ensure its long-term stable storage in aircraft equipment bays, reducing aircraft maintenance costs. Furthermore, its oleophobicity provides excellent resistance to re-ignition, protecting aircraft power compartments from secondary fire damage. X-ray photoelectron spectroscopy (XPS) analysis revealed the formation of new Mg-O-Si bonds in M-BDP, indicating successful grafting of the PFDTMS modifier onto Mg(OH)₂. Additionally, both BDP and M-BDP exhibited multistage thermal decomposition processes. The first stage of decomposition for both materials could be considered a single-step reaction, and the calculated kinetic parameters provided accurate predictions. Thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS) results indicated that, compared to BDP, M-BDP produced significantly lower amounts of combustible gases (CH₄) relative to inert gases (H₂O and CO₂) during thermal decomposition, which does not compromise its fire-extinguishing capabilities. Moreover, M-BDP demonstrated a reduced minimum extinguishing concentration by 16.6 gm⁻³ and a shortened extinguishing time by 242 ms compared to BDP. For aviation kerosene, the re-ignition time delay for M-BDP was significantly extended to 10.9 s, compared to 4 ms for BDP. Research on the thermal stability of M-BDP contributes to a deeper understanding of its storage stability under high-temperature conditions and its mechanism of combustion suppression in fire zones. Furthermore, the results suggest that M-BDP has potential as a replacement for halon extinguishing agents in aircraft engine nacelles.