Robust hydrophobic modification of para‐aramid nanofibers/polyvinyl alcohol composite aerogels with 1H,1H,2H,2H‐perfluorooctyltriethoxysilane

Abstract Aerogels are frequently exposed to moisture or come into direct contact with water in real‐world applications, posing a threat to their stable performance. Herein, based on the characteristic that the liquid phase can efficiently diffuse in the solid cross‐linked network of gels, a robust hydrophobic modification approach for para‐aramid nanofibers/polyvinyl alcohol (ANFs/PVA) composite aerogels with 1H,1H,2H,2H‐perfluorooctyltriethoxysilane (PFOTES) is demonstrated. The type of solvent, the concentration of hydrochloric acid (HCl) required promoting PFOTES hydrolysis, and the treatment time for hydrophobic modification are discussed individually. The ANFs/PVA/PFOTES aerogels with a water contact angle of 131.0° were obtained through supercritical fluid drying employing acetone as the solvent, with a concentration of 0.1 mol/L HCl of 0.35 vol%, and a treatment duration of 2 h. The hydrogen bond between ANFs and PVA, and the grafting of PFOTES on PVA have both been verified by Fourier‐transform infrared spectroscopy. The porous structure of the modified aerogels was improved simultaneously, according to scanning electron microscope and Brunauer–Emmett–Teller characterizations. With the help of a thermal imaging camera, ANFs/PVA/PFOTES aerogels exhibit stable thermal insulation capability in low temperature and humid environments, which holds great promise for a wide range of applications.