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Biomimetic Foams of High Mechanical Performance Based on Nanostructured Cell Walls Reinforced by Native Cellulose Nanofibrils
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.ORCID-id: 0000-0002-4583-723X
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.
KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer.ORCID-id: 0000-0001-5818-2378
2008 (engelsk)Inngår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 20, nr 7, s. 1263-1269Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

 A bioinspired foam in which cellulose nanofibrils are used to reinforce cell walls (ca. 3 mu m) is presented. The nanocomposite foams are prepared by a lyophilization technique and show composite structure at the cell-wall scale. The nanocellulosic network shows remarkable mechanical performance, expressed in much-improved modulus and yield strength compared with the neat starch foam.

sted, utgiver, år, opplag, sider
Weinheim: Wiley-VCH Verlag GmbH , 2008. Vol. 20, nr 7, s. 1263-1269
Emneord [en]
ABS resins, Biodegradable polymers, Biomimetics, Cellulose, Cellulose derivatives, Dewatering, Hydrolysis, Metallic matrix composites, Microbial fuel cells, Nanocomposites, Nanostructured materials, Polymer matrix composites, Polysaccharides, Reinforcement, Water content
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-9653DOI: 10.1002/adma.200701215ISI: 000255348900007Scopus ID: 2-s2.0-54949096154OAI: oai:DiVA.org:kth-9653DiVA, id: diva2:126834
Merknad
QC 20100901Tilgjengelig fra: 2008-11-26 Laget: 2008-11-24 Sist oppdatert: 2017-12-14bibliografisk kontrollert
Inngår i avhandling
1. Bio-inspired cellulose nanocomposites and foams based on starch matrix
Åpne denne publikasjonen i ny fane eller vindu >>Bio-inspired cellulose nanocomposites and foams based on starch matrix
2008 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In 2007 the production of expanded polystyrene (EPS) in the world was over 4 million tonnes and is expected to grow at 6 percent per year. With the increased concern about environmental protection, alternative biodegradable materials from renewable resources are of interest. The present doctoral thesis work successfully demonstrates that starch-based foams with mechanical properties similar to EPS can be obtained by reinforcing the cell-walls in the foams with cellulose nanofibers (MFC).

High cellulose nanofiber content nanocomposites with a highly plasticized (50/50) glycerol-amylopectin starch matrix are successfully prepared by solvent-casting due to the high compatibility between starch and MFC. At 70 wt% MFC, the nanocomposites show a remarkable combination of high tensile strength, modulus and strain to failure, and consequently very high work to fracture. The interesting combination of properties are due to good dispersion of nanofibers, the MFC network, nanofiber and matrix properties and favorable nanofiber-matrix interaction.

The moisture sorption kinetics (30% RH) in glycerol plasticized and pure amylopectin film reinforced with cellulose nanofibers must be modeled using a moisture concentration-dependent diffusivity in most cases. The presence of cellulose nanofibers has a strong reducing effect on the moisture diffusivity. The decrease in zero-concentration diffusivity with increasing nanofiber content could be due to geometrical impedance, strong starch-MFC molecular interaction and constrained swelling due to the cellulose nanofiber network present.

Novel biomimetic starch-based nanocomposite foams with MFC contents up to 40 wt% are successfully prepared by freeze-drying. The hierarchically structured nanocomposite foams show significant increase in mechanical properties in compression compared to neat starch foam. Still, better control of the cell structure could further improve the mechanical properties. The effect of cell wall composition, freeze-drying temperature and freezing temperature on the resulting cell structure are therefore investigated. The freeze-drying temperature is critical in order to avoid cell structure collapse. By changing the starch content, the cell size, anisotropy ratio and ratio between open and closed cells can be altered. A decrease in freezing temperature decreases the cell size and increases the anisotropy ratio.

Finally, mechanical properties obtained in compression for a 30 wt% MFC foam prepared by freeze-drying demonstrates comparable properties (Young's modulus and yield strength) to expanded polystyrene at 50% RH and similar relative density. This is due to the reinforcing cellulose nanofiber network within the cell walls.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2008. s. viii, 50
Serie
Trita-CHE-Report, ISSN 1654-1081 ; 2008:75
Emneord
starch, cellulose nanofibers, foam, nanocomposites, cushioning materials, biodegradable, expanded polystyrene, mechanical properties, diffusion
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-9666 (URN)978-91-7415-189-3 (ISBN)
Disputas
2008-12-16, F3, Lindstedrsvägen 26, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad
QC 20100913Tilgjengelig fra: 2008-12-03 Laget: 2008-11-26 Sist oppdatert: 2011-09-05bibliografisk kontrollert

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