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Ultra-Porous Nanocellulose Foams: A Facile and Scalable Fabrication Approach

1
Cellulose and Wood Materials, Swiss Federal Laboratories for Materials Science and Technology (Empa), 8600 Dübendorf, Switzerland
2
Department of Materials Science, University of Milano—Bicocca, 20126 Milano, Italy
3
State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Key Laboratory of Environment and Control for Flight Vehicle, International Center for Applied Mechanics, School of Aerospace, Xi’an Jiaotong University, Xi’an 710049, China
*
Authors to whom correspondence should be addressed.
Nanomaterials 2019, 9(8), 1142; https://doi.org/10.3390/nano9081142
Received: 1 July 2019 / Revised: 22 July 2019 / Accepted: 31 July 2019 / Published: 9 August 2019
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Abstract

Cellulose nanofibril foams are cellulose-based porous materials with outstanding mechanical properties, resulting from the high strength-to-weight ratio of nanofibrils. Here we report the development of an optimized fabrication process for highly porous cellulose foams, based on a well-controlled freeze-thawing-drying (FTD) process at ambient pressure. This process enables the fabrication of foams with ultra-high porosity, up to 99.4%, density of 10 mg/cm3, and liquid (such as oil) absorption capacity of 100 L/kg. The proposed approach is based on the ice-templating of nanocellulose suspension in water, followed by thawing in ethanol and drying at environmental pressures. As such, the proposed fabrication route overcomes one of the major bottle-necks of the classical freeze-drying approach, by eliminating the energy-demanding vacuum drying step required to avoid wet foam collapse upon drying. As a result, the process is simple, environmentally friendly, and easily scalable. Details of the foam development fabrication process and functionalization are thoroughly discussed, highlighting the main parameters affecting the process, e.g., the concentration of nanocellulose and additives used to control the ice nucleation. The foams are also characterized by mechanical tests and oil absorption measurements, which are used to assess the foam absorption capability as well as the foam porosity. Compound water-in-oil drop impact experiments are used to demonstrate the potential of immiscible liquid separation using cellulose foams. View Full-Text
Keywords: cellulose nanomaterials; nanofibrils; foam; oil absorption; hydrophobicity; ice-templating; freeze-drying; freeze-thawing; ambient pressure drying; compound drops cellulose nanomaterials; nanofibrils; foam; oil absorption; hydrophobicity; ice-templating; freeze-drying; freeze-thawing; ambient pressure drying; compound drops
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Antonini, C.; Wu, T.; Zimmermann, T.; Kherbeche, A.; Thoraval, M.-J.; Nyström, G.; Geiger, T. Ultra-Porous Nanocellulose Foams: A Facile and Scalable Fabrication Approach. Nanomaterials 2019, 9, 1142.

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