Experimental study on potential fire hazards of hydrophobic silica aerogel felts under high-temperature conditions

Hydrophobic silica aerogel felts are widely utilized as high-performance thermal insulation materials; however, their reaction-to-fire performance and smoke hazards under severe thermal radiation remain insufficiently characterized. This study evaluates the thermal degradation and combustion hazards of four commercial hydrophobic silica aerogel felts using TG-DSC , bomb calorimetry, and cone calorimetry under radiant heat fluxes of 35–55 kW/m 2 . The experimental results demonstrate a positive correlation between the organic methyl group (-CH 3 ) content and macroscopic fire hazard parameters across the investigated commercial samples. Among the tested specimens, Sample ALS , which possesses the highest initial organic methyl mass fraction, exhibits the highest ignition susceptibility, yielding an average time to ignition of 5.3 ± 4.0 s, a peak heat release rate of 36.44 ± 4.12 kW/m 2 under 55 kW/m 2 , and sustained flaming combustion. In contrast, specimens with lower estimated methyl loadings (0.40–0.83 wt %) primarily undergo flameless smoldering or thermal decomposition. Experimental observations indicate that the low thermal conductivity of the aerogel matrix is considered to promote localized heat accumulation, which is postulated to sustain subsurface residual pyrolysis following surface flame extinction. Furthermore, Sample SR exhibits significant smoke obscuration, with its average specific extinction area reaching 2798.09 ± 245.30 m 2 /kg at 55 kW/m 2 , presenting critical visibility hazards. This work provides quantitative benchmark data for evaluating the fire and smoke hazards of commercial hydrophobic silica aerogel felts under severe radiant heat exposure.