Multiscale Design for Robust, Thermal Insulating, and Flame Self-Extinguishing Cellulose Foam
Small (Weinheim an der Bergstrasse, Germany)(2023)
摘要
Cellulose foams are in high demand in an era of prioritizing environmental consciousness. Yet, transferring the exceptional mechanical properties of cellulose fibers into a cellulose network remains a significant challenge. To address this challenge, an innovative multiscale design is developed for producing cellulose foam with exceptional network integrity. Specifically, this design relies on a combination of physical cross-linking of the microfibrillated cellulose (MFC) networks by cellulose nanofibril (CNF) and aluminum ion (Al3+), as well as self-densification of the cellulose induced by ice-crystal templating, physical cross-linking, solvent exchange, and evaporation. The resultant cellulose foam demonstrates a low density of 40.7 mg cm-3, a high porosity of 97.3%, and a robust network with high compressive modulus of 1211.5 +/- 60.6 kPa and energy absorption of 77.8 +/- 1.9 kJ m-3. The introduction of CNF network and Al3+ cross-linking into foam also confers excellent wet stability and flame self-extinguish ability. Furthermore, the foam can be easily biodegraded in natural environments , re-entering the ecosystem's carbon cycle. This strategy yields a cellulose foam with a robust network and outstanding environmental durability, opening new possibilities for the advancement of high-performance foam materials. A multiscale design strategy is proposed to fabricate mechanically robust cellulose foam with well-balanced attributes including low density, high porosity, flame self-extinguishing, biodegradability, and process sustainability. This strategy effectively enhances performance through the utilization of physical and ionic cross-linking via cellulose nanofibrils and aluminum ion (Al3+), coupled with structural densification brought about by ice-crystal templating, cross-linking, and solvent exchange/evaporation.image
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关键词
air drying, cellulose, cross-linkings, fibrillation, foams
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