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 paraaramid 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.

Super-Repellent and Flexible Lubricant-Infused Bacterial Nanocellulose Membranes with Superior Antithrombotic, Antibacterial, and Fatigue Resistance Properties

“…Further, BNC-S exhibited other peaks at 810, 910, and 1210 cm −1 ; the first is attributed to −CF 3 groups and others to −CF 2 − bonds. 47,48 The molecular structure of PFPP has plenty of −CF 2 − bonds; 49 therefore, its correlating peaks were intensified in the spectrum of BNC-L samples. However, the peak of −CF 3 remained evident as this group is only introduced by TPFS molecules and is not available in the structure of PFPP molecules.…”

‘Rigid‐soft’ synergistic effects to improve the microstructure and superflexibility properties of aramid nanofiber aerogel

“…Its thermal insulation effect is slightly reduced with the increased CNF/PVA, which is closely related to the pore structure. 25,26 Compared with ANF aerogel, the pore structure of composite aerogel has better thermal insulation performance and good heat resistance due to the joint action of flexible PVA and semi-rigid CNF. It can also be clearly seen in SEM that appropriate amount of CNF/PVA is helpful to adjust the structure of ANF aerogel, while excessive CNF/PVA will worsen the pore characteristics.…”