Research on the Regulation and Optimization of Low-Temp Expansion and Carbonization of DI Expandable Fire Extinguishing Agent

In coalfield fire management, the direct-injection (DI) sealing technique has gained attention due to its water conservation efficiency. Its effectiveness hinges crucially on selecting an appropriate sealing material, where intumescent flame retardants (IFRs) excel due to their impressive carbonization abilities. However, standard IFRs struggle to achieve adequate carbonization at temperatures between 100 and 300 °C, limiting their usefulness in sealing fire zones. Furthermore, the reaction of IFRs in coal fire zones differs from that in polymers, necessitating independent expansion and carbonization processes. Consequently, there is a need to redesign the “three-source” reaction system of IFRs. This study delves into optimizing the composition and ratios of the “three-source” in IFRs. Through thermal gravimetric analysis (TGA) and isothermal carbonization tests, key factors (temperature, composition ratio) influencing the low-temperature expansion and carbonization behavior of IFRs are elucidated. Specifically, using low-polymerization ammonium polyphosphate (APP) as the acid source notably decreased the initial decomposition temperature (T¹_onset) of IFRs. Coupled with glucose (GL), the T¹_onset dropped to 134 °C while preserving a significant residual carbon yield. Incorporating urea (UR) as the gas source further reduces the T¹_onset to 112 °C, demonstrating excellent low-temperature carbonization. Notably, when the GL:APP:UR ratio is adjusted to 4:1:0.5 ~ 4:1:1, the IFR effectively forms a stable sealing layer at low temperatures. Additionally, Fourier transform infrared spectroscopy (FTIR) analysis reveals the evolution of carbon layer functional groups across temperatures, enhancing understanding of the complex chemical reactions during low-temperature carbonization of IFRs. This innovative formulation offers a novel approach for coalfield fire suppression.