Hydrophobic, Fire–Resistant, and Compressible Aramid Nanofiber Aerogels Enabled by In Situ Polysiloxane Cross-Linking

Abstract

Aramid nanofiber (ANF) aerogels are promising candidates for thermal protection and structural applications; however, their practical implementation remains substantially constrained by the intrinsic trade–off between mechanical robustness and fire–resistant functionality. In this study, a mechanically robust, highly hydrophobic, and fire–resistant hybrid aerogel was developed using a green high–pressure homogenization process coupled with in situ polysiloxane cross-linking. Through the construction of a rigid–flexible interpenetrating network, the resulting aerogel overcomes the inherent fragility associated with conventional physical entanglements while achieving an ultralow density of 4.62–9.48 mg cm–3, pronounced superelasticity (96.7% height recovery and 79% modulus retention after 100 cycles), and excellent fire resistance (LOI = 33). Notably, the aerogel exhibits remarkable structural and functional integrity following combustion because in situ ceramization converts the polysiloxane network into a thermally stable Si–O–Si/Si–C barrier, enabling retention of 92% of its compressive strength while preserving substantial surface hydrophobicity, as evidenced by a water contact angle of 132.7° even after direct flame exposure. To demonstrate its practical applicability to fire–prone oil–spill scenarios, the aerogel displays synergistic adsorption and flame–retardant performance in simulated burning oil spills, with a high absorption capacity of 60–180 g g–1 and rapid self–extinguishing behavior (<30 s). These findings establish a versatile design strategy for engineering multifunctional aerogels that integrate mechanical resilience, fire safety, and post–combustion structural integrity.