Thermally Insulating and Moisture-Resilient Foams Based on Upcycled Aramid Nanofibers and Nanocellulose.

Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. We have prepared super-insulating foams from upcycled acid-treated aramid nanofibers (upANF A ) obtained from Kevlar ® yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANF A /CNF-based foams with an upANF A content of up to 40 wt.% displayed high thermal stability and a very low thermal conductivity of 18-23 mW m -1 K -1 perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANF A /CNF foams was found to decrease with increasing upANF A content (5-20 wt.%). The super-insulating properties of the CNF-upANF A hybrid foams were related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANF A and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar ® , and this study could hopefully inspire efforts to upcycle textile waste into high-performance products. This article is protected by copyright. All rights reserved.