Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Cellulose Nanofibril Networks and Composites: Preparation, Structure and Properties
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [sv]

Träbaserade cellulosananofibriller är intressanta som förstärkande fas i polymera nanokompositer; detta främst på grund av den kristallina cellulosans höga styvhet och på grund av nanofibrillernas förmåga att bilda nätverk. Cellulosananofibriller kan användas i form av mikrokristallin cellulosa, MCC, som har lågt längd/diameter förhållande, eller i form av mikrofibrillerad cellulosa, MFC, med högt längd/diameter förhållande. Målet med det här arbetet är att studera struktur-egenskapsförhållanden för nanofibrillnätverk och kompositer.

Nanokompositer baserade på MCC och termoplastisk polyuretan tillverkades genom in-situ polymerisation. Cellulosafibrillerna var väl dispergerade i matrisfasen och kompositen visade ökad styvhet, styrka samt brottöjning. Dessa förbättningar antas bero på stark interaktion mellan polyuretan och cellulosananofibrillerna.

En metod som underlättar mikrofibrillering av massafiberns cellvägg under homogenisering har utvecklats. Massan förbehandlades med ett enzym innan homogenisering. Den här metoden förenklade mikrofibrilleringen och mekanismerna diskuteras. De resulterande MFC-nanofibrillerna hade högt längd/diameter förhållande.

Filmer har tillverkats av MFC-nanofibriller och filmernas struktur samt mekaniska egenskaper har studerats. Röntgendiffraktion och SEM visar att nanofibrilerna är mer orienterade i planet än i rymden. SEM och densitetsmätningar visar även att filmerna har en porös struktur. Resultaten från dragprovning visade att filmernas brottstyrka är beroende av molekylvikten för cellulosan. Nanofibrillerna med högst molekylvikt visade en E-modul på 13.2 GPa, brottstyrkan var 214 MPa och brottöjningen 10.1%.

Kompositer med hög fiberhalt har tillverkats genom tillsats av melaminformaldehyd till MFC-filmer. Dessa kompositer visar ökad styvhet och styrka på bekostnad av brottöjningen. Kompositer har också tillverkats genom impregnering av MFC-nätverk med en hyperförgrenad polymer som tvärbands. DMA visar två Tg för kompositerna med 0.26 och 0.43 volymfraktion nanofibriller; matrisens Tg samt ytterligare ett Tg vid högre temperatur. Detta motsvarar molekyler med lägre mobilitet på grund av ökad interaktion med nanofibrillernas ytor.

Abstract [en]

The cellulose nanofibril from wood is an interesting new material constituent that can provide strong reinforcement in polymer nanocomposites due to the high stiffness of the cellulose crystals and the network formation characteristics of the nanofibrils. Cellulose nanofibrils can be used either in the form of low aspect ratio microcrystalline cellulose, MCC, or as high aspect ratio microfibrillated cellulose, MFC. The objective is to study structure-property relationships for cellulose nanofibril networks and composites.

Nanocomposites based on MCC and thermoplastic polyurethane were prepared by in-situ polymerization. The cellulose nanofibrils were successfully dispersed in the matrix and the composites showed improvements in stiffness, strength, as well as in strain-to-failure. Cellulose nanofibrils reinforce the physical rubber network by strong molecular interaction with the rubber.

A method that facilitates microfibrillation of the pulp cell wall during homogenization has been developed. The pulps were treated with a combination of beating and enzymatic treatment prior to homogenization. The enzymatic pretreatment was found to facilitate the microfibrillation and the mechanisms are discussed. The resulting MFC nanofibrils were of high aspect ratio.

Cellulose nanofibril networks of high toughness were prepared from MFC and studied with respect to the structure and mechanical properties. These films have a porous structure and the nanofibrils are more in-plane than in-space oriented. Tensile testing showed that the strength is dependent on the average molecular weight of the cellulose. The MFC of the highest molecular weight showed a modulus of 13.2 GPa, tensile strength as high as 214 MPa and 10.1% strain-to-failure, at a porosity of 28%.

Composites of high fiber content have been prepared by addition of melamine formaldehyde to MFC films. These composites show increased stiffness and strength, at the cost of strain-to-failure. Composites were also prepared by impregnating MFC nanofibril networks with a hyperbranched polymer. The matrix was crosslinked and strong interactions with the nanofibrils were formed. By DMA two Tg’s were observed for the composites with 0.26 and 0.43 volume fraction nanofibrils. The Tg of the matrix was observed as well as a Tg at higher temperatures. This corresponds to molecules with constrained mobility by increased interactions with the cellulose nanofibril surfaces.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , 51 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:3
Keyword [en]
cellulose nanocomposites, microfibrillated cellulose, nanofibrils, biofibers, mechanical properties, deformation mechanisms, molar mass, endoglucanase
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4610ISBN: 978-91-7178-849-8 (print)OAI: oai:DiVA.org:kth-4610DiVA: diva2:13082
Public defence
2008-02-08, F3, F-byggnaden, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100810Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2010-08-10Bibliographically approved
List of papers
1. A High Strength Nanocomposite Based on Microcrystalline Cellulose and Polyurethane
Open this publication in new window or tab >>A High Strength Nanocomposite Based on Microcrystalline Cellulose and Polyurethane
2007 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 12, 3687-3692 p.Article in journal (Refereed) Published
Abstract [en]

A high-strength elastomeric nanocomposite has successfully been prepared by dispersing microcrystalline cellulose in a polyurethane matrix. The resulting nanocomposites show increased strain-to-failure in addition to increased stiffness and strength compared to the unfilled polyurethane. The optimal composite contained 5 wt % cellulose. The average true strength for this composition was 257 MPa, compared with 39 MPa for the neat polyurethane, and showed the highest strain-to-failure. The improvements of stiffness, strength, as well as strain-to-failure are believed to be due to good interaction, by both covalent and hydrogen bonds, between the polyurethane and the cellulose nanofibrils.

Keyword
Cellulosic resins; Covalent bonds; Elastomers; Hydrogen bonds; Microcrystals; Polymer matrix; Polyurethanes; Stiffness; Cellulose nanofibrils; Strain-to-failure
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-7907 (URN)10.1021/bm701061t (DOI)000251547600001 ()2-s2.0-38049070254 (Scopus ID)
Note

QC 20100810

Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-14Bibliographically approved
2. An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers
Open this publication in new window or tab >>An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers
2007 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 43, no 8, 3434-3441 p.Article in journal (Refereed) Published
Abstract [en]

Microfibrillated cellulose nanofibers (MFC) provide strong reinforcement in polymer nanocomposites. In the present study, cellulosic wood fiber pulps are treated by endoglucanases or acid hydrolysis in combination with mechanical shearing in order to disintegrate MFC from the wood fiber cell wall. After successful disintegration, the MFC nanofibers were studied by atomic force microscopy (AFM). Enzyme-treatment was found to facilitate disintegration, and the MFC nanofibers produced also showed higher average molar mass and larger aspect ratio than nanofibers resulting from acidic pretreatment.

Keyword
microfibrillated cellulose; nanofibers; endoglucanase; hydrolysis; degree of polymerization
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-7908 (URN)10.1016/j.eurpolymj.2007.05.038 (DOI)000249446700034 ()2-s2.0-34547418742 (Scopus ID)
Note
QC 20100810Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-14Bibliographically approved
3. Structure and Properties of Cellulose Nanocomposite Films Containing Melamine Formaldehyde
Open this publication in new window or tab >>Structure and Properties of Cellulose Nanocomposite Films Containing Melamine Formaldehyde
2007 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 106, no 4, 2817-2824 p.Article in journal (Refereed) Published
Abstract [en]

Films of high Young's modulus and low density are of interest for application as loudspeaker membranes. In the present study nanocomposite films were prepared from microfibrillated cellulose (MFC) and from MFC in combination with melamine formaldehyde (MF). The prepared materials were Studied with respect to structure as well as physical and mechanical properties. Studies in SEM and calculation of porosity showed that these materials have a dense paper-like structure. The moisture sorption isotherms were measured and showed that Moisture content decreased in the presence of ME Mechanical properties were studied by dynamical mechanical thermal measurements as well as by tensile tests. Cellulose films showed an average Young's modulus of 14 GPa while the nanocomposites showed an average Young's modulus as high as 16.6 GPa and average tensile strength as high as 142 M.Pa. By controlling composition and structure, the range of properties of these materials can extend the property range available for existing materials. The combination of comparatively high mechanical damping and high sound propagation velocity is of technical interest.

Keyword
microfibrillated cellulose; biofibers; cellulose nanocomposites; mechanical properties; loudspeaker membrane
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-7909 (URN)10.1002/app.26946 (DOI)000249590700086 ()2-s2.0-35148848649 (Scopus ID)
Note
QC 20100810Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-14Bibliographically approved
4. Cellulose nanopaper structures of high toughness
Open this publication in new window or tab >>Cellulose nanopaper structures of high toughness
Show others...
2008 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 9, no 6, 1579-1585 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose nanofibrils offer interesting potential as a native fibrous constituent of mechanical performance exceeding the plant fibers in current use for commercial products. In the present study, wood nanofibrils are used to prepare porous cellulose nanopaper of remarkably high toughness. Nanopapers of different porosities and from nanofibrils of different molar mass are prepared. Uniaxial tensile tests are performed and structure-property relationships are discussed. The high toughness of highly porous nanopaper is related to the nanofibrillar network structure and high mechanical nanofibril performance. Also, molar mass correlates with tensile strength. This indicates that nanofibril fracture controls ultimate strength. Furthermore, the large strain-to-failure means that mechanisms, such as interfibril slippage, also contributes to inelastic deformation in addition to deformation of the nanofibrils themselves.

Keyword
Cellulose; Deformation; Fibers; Fracture fixation; Molar mass; Petroleum products; Tensile strength; Tensile testing; American Chemical Society (ACS); Commercial products; High toughness; Inelastic deformations; Large strains; mechanical performances; Nano-fibrils; Nanofibrillar; Network structures; Plant fibers; Strength (IGC: D5/D6); Structure property relationships; ultimate strength; Uniaxial tensile testing
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-7910 (URN)10.1021/bm800038n (DOI)000256635100011 ()2-s2.0-46849094688 (Scopus ID)
Note
QC 20100810. Uppdaterad från submitted till published (20100810).Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2017-12-14Bibliographically approved
5. A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril networks
Open this publication in new window or tab >>A new nanocomposites approach for strong attachment of polymer matrices to cellulose nanofibril networks
Show others...
(English)Manuscript (Other academic)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-7911 (URN)
Note
QC 20100810Available from: 2008-01-21 Created: 2008-01-21 Last updated: 2010-08-16Bibliographically approved

Open Access in DiVA

fulltext(1528 kB)1626 downloads
File information
File name FULLTEXT01.pdfFile size 1528 kBChecksum MD5
ddc008ec8e46e0371cb5acb29f633b28e5cbfce39348cfd82ceffc0f3955d54e3b61b8c8
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Henriksson, Marielle
By organisation
Fibre and Polymer Technology
Materials Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 1626 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1627 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf