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Strong and Tough Cellulose Nanopaper with High Specific Surface Area and Porosity
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Biotechnology (BIO), Glycoscience.ORCID iD: 0000-0001-9832-027X
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.ORCID iD: 0000-0001-5818-2378
2011 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 10, 3638-3644 p.Article in journal (Refereed) Published
Abstract [en]

In order to better understand nanostructured fiber networks, effects from high specific surface area of nanofibers are important to explore. For cellulose networks, this has so far only been achieved in nonfibrous regenerated cellulose aerogels. Here, nanofibrillated cellulose (NFC) is used to prepare high surface area nanopaper structures, and the mechanical properties are measured in tensile tests. The water in NFC hydrogels is exchanged to liquid CO(2), supercritical CO(2), and tert-butanol, followed by evaporation, supercritical drying, and sublimation, respectively. The porosity range is 40-86%. The nanofiber network structure in nanopaper is characterized by FE-SEM and nitrogen adsorption, and specific surface area is determined. High-porosity TEMPO-oxidized NFC nanopaper (56% porosity) prepared by critical point drying has a specific surface area as high as 48(2) m(2) g(-1). The mechanical properties of this nanopaper structure are better than for many thermoplastics, but at a significantly lower density of only 640 kg m(-3). The modulus is 1.4 GPa, tensile strength 84 MPa, and strain-to-failure 17%. Compared with water-dried nanopaper, the material is softer with substantially different deformation behavior.

Place, publisher, year, edition, pages
2011. Vol. 12, no 10, 3638-3644 p.
Keyword [en]
tempo-mediated oxidation, composite membranes, native cellulose, nanofibers, aerogels, polymer, nanoparticles, density, liquid
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:kth:diva-46853DOI: 10.1021/bm2008907ISI: 000295602600031ScopusID: 2-s2.0-80053988282OAI: diva2:454361
QC 20111107. Uppdaterad från Manuskript till Artikel (20111111)Available from: 2011-11-07 Created: 2011-11-07 Last updated: 2011-11-11Bibliographically approved
In thesis
1. Nanofiber networks, aerogels and biocomposites based on nanofibrillated cellulose from wood
Open this publication in new window or tab >>Nanofiber networks, aerogels and biocomposites based on nanofibrillated cellulose from wood
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanofibrillated cellulose (NFC) from wood is an interesting material constituent of high strength and high aspect ratio, which easily forms networks through interfibril secondary bonding including hydrogen bonds. This has been exploited in preparation of new materials, which extend the range of properties for existing cellulosic materials. The objective is to explore processing-structure and structure-property relationships in NFC materials.

Dense networks of NFC, referred to as “nanopaper” having a random-in-the-plane orientation of the fibrils have been successfully prepared by a papermaking-like process involving vacuum filtration and water evaporation using laboratory papermaking equipment. Large, flat and transparent nanopaper sheets have thus been prepared in a relatively short time. Using the same preparation route, NFC was used to reinforce pulped wood fibers in dense network structures. NFC networks formed in the pore space of the wood fiber network give an interesting hierarchical structure of reduced porosity. These NFC/wood fiber biocomposites have greater strength, greater stiffness and greater strain-to-failure than reference networks of wood fibers only. In particular, the work to fracture (area under the stress-strain curve) is doubled with an NFC content of only 2%.

The papermaking preparation route was extended to prepare nanocomposites of high NFC content with a cellulose derivative matrix (hydroxyethyl cellulose, HEC) strongly associated to the NFC. Little HEC was lost during filtration. The NFC/HEC composites have high work to fracture, higher than that of any reported cellulose composite. This is related to NFC network characteristics, and HEC properties and its nanoscale distribution and association with NFC.

Higher porosity NFC nanopaper networks of high specific surface area were prepared by new routes including supercritical drying, tert-butanol freeze-drying and CO2 evaporation. Light-weight porous nanopaper materials resulted with mechanical properties similar to thermoplastics but with a much lower density and a specific surface area of up to 480 m2/g.

Freeze-drying of hydrocolloidal NFC dispersions was used to prepare ultra-high porosity foam structures. The NFC foams have a cellular foam structure of mixed open/closed cells and “nanopaper” cell wall. Control of density and mechanical properties was possible by variation of NFC concentration in the dispersion. A cellulose I foam of the highest porosity ever reported (99.5%) was prepared. The NFC foams have high ductility and toughness and may be of interest for applications involving mechanical energy absorption. Freeze-drying of NFC suspended in tert-butanol gave highly porous NFC network aerogels with a large surface area. The mechanical behavior was significantly different from NFC foams of similar density due to differences in deformation mechanisms for NFC nanofiber networks.


Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. 74 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2011:024
Nanofibrillated cellulose, nanopaper, nanofiber, biocomposites, aerogel, foam
National Category
Materials Engineering
urn:nbn:se:kth:diva-32079 (URN)978-91-7415-931-8 (ISBN)
Public defence
2011-04-27, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
QC 20110406Available from: 2011-04-06 Created: 2011-04-05 Last updated: 2011-11-11Bibliographically approved

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