Thermally Insulating and Moisture-Resilient Foams Based on Upcycled Aramid Nanofibers and Nanocellulose.
basic_science · Level V
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- Record sourced from PubMed, PMID 37735848.
- Also identified by DOI 10.1002/adma.202305195.
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Abstract
Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. Super-insulating foams are prepared from upcycled acid-treated aramid nanofibers (upANF<sub>A</sub> ) obtained from Kevlar yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANF<sub>A</sub> /CNF-based foams with an upANF<sub>A</sub> content of up to 40 wt% display high thermal stability and a very low thermal conductivity of 18-23 mW m<sup>-1</sup> K<sup>-1</sup> perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANF<sub>A</sub> /CNF foams is found to decrease with increasing upANF<sub>A</sub> content (5-20 wt%). The super-insulating properties of the CNF-upANF<sub>A</sub> hybrid foams are related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANF<sub>A</sub> and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar, and this study can hopefully inspire efforts to upcycle textile waste into high-performance products.