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Compression-moulded and multifunctional cellulose network materials
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. (WWSC)
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulose-based materials are widely used in a number of important applications (e.g. paper, wood, textiles). Additional developments are suggested by the growing interest for natural fibre-based composite and nanocomposite materials. The motivation is not only in the economic and ecological benefits, but is also related to advantageous properties and characteristics. The objective of this thesis is to provide a better understanding of process-structure-property relationships in some novel cellulose network materials with advanced functionalities, and showing potential large-scale processability. An important result is the favourable combination of mechanical properties observed for network-based cellulose materials.

Compression-moulding of cellulose pulp fibres under high pressure (45 MPa) and elevated temperature (120 – 180 oC) provides an environmentally friendly process for preparation of stiff and strong cellulose composite plates. The structure of these materials is characterized at multiple scales (molecular, supra-molecular and microscale). These observations are related to measured reduction in water retention ability and improvement in mechanical properties.

In a second part, cellulose nanofibrils (NFC) are functionalized with in-situ precipitated magnetic nanoparticles and formed into dense nanocomposite materials with high inorganic content. The precipitation conditions influence particle size distributions, which in turn affect the magnetic properties of the material. Besides, the decorated NFC network provides high stiffness, strength and toughness to materials with very high nanoparticle loading (up to 50 vol.%).

Subsequently, a method for impregnation of wet NFC network templates with a thermosetting epoxy resin is developed, enabling the preparation of well-dispersed epoxy-NFC nanocomposites with high ductility and moisture durable mechanical properties. Furthermore, cellulose fibrils interact positively with the epoxy during curing (covalent bond formation and accelerated curing). Potential large scale development of epoxy-NFC and magnetic nanocomposites is further demonstrated with the manufacturing of 3D shaped compression-moulded objects.

Finally, the wet impregnation route developed for epoxy is adapted to prepare UV-curable NFC nanocomposite films with a hyperbranched polymer matrix. Different chemical modifications are applied to the NFC in order to obtain moisture durable oxygen barrier properties.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , p. 80
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2013:45
Keyword [en]
compression-moulding, cellulose fibre, nanocomposite, magnetic nanoparticle, epoxy, UV curing, oxygen barrier
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-133564ISBN: 978-91-7501-911-6 (print)OAI: oai:DiVA.org:kth-133564DiVA, id: diva2:662131
Public defence
2013-11-29, K1, Teknikringen 56, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20131111

Available from: 2013-11-11 Created: 2013-11-06 Last updated: 2013-11-11Bibliographically approved
List of papers
1. A non-solvent approach for high-stiffness all-cellulose biocomposites based on pure wood cellulose
Open this publication in new window or tab >>A non-solvent approach for high-stiffness all-cellulose biocomposites based on pure wood cellulose
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2010 (English)In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 70, no 12, p. 1704-1712Article in journal (Refereed) Published
Abstract [en]

All-cellulose composites are commonly prepared using cellulose solvents. In this study, moldable all-cellulose I wood fiber materials of high cellulose purity (97%) were successfully compression molded. Water is the only processing aid. The material is interesting as a "green" biocomposite for industrial applications. Dissolving wood fiber pulps (Eucalyptus hardwood and conifer softwood) are used and the influence of pulp origin, beating and pressing temperature (20-180 degrees C) on supramolecular cellulose nanostructure is studied by solid state CP/MAS C-13 NMR. Average molar mass is determined by SEC to assess process degradation effects. Mechanical properties are determined in tensile tests. High-density composites were obtained with a Young's modulus of up to 13 GPa. In addition, nanoscale cellulose fibril aggregation was confirmed due to processing, and resulted in a less moisture sensitive material.

Keyword
Wood, Mechanical properties, CP/MAS C-13 NMR, Heat treatment, Isostatic pressing
National Category
Chemical Sciences Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-26690 (URN)10.1016/j.compscitech.2010.06.016 (DOI)000281998000006 ()2-s2.0-77955846808 (Scopus ID)
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-26 Last updated: 2017-12-12Bibliographically approved
2. Compression molded wood pulp biocomposites: A study of hemicellulose influence on cellulose supramolecular structure and material properties
Open this publication in new window or tab >>Compression molded wood pulp biocomposites: A study of hemicellulose influence on cellulose supramolecular structure and material properties
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2012 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 3, p. 751-760Article in journal (Refereed) Published
Abstract [en]

In this study, the importance of hemicellulose content and structure in chemical pulps on the property relationships in compression molded wood pulp biocomposites is examined. Three different softwood pulps are compared; an acid sulfite dissolving grade pulp with high cellulose purity, an acid sulfite paper grade pulp and a paper grade kraft pulp, the latter two both containing higher amounts of hemicelluloses. Biocomposites based the acid sulfite pulps exhibit twice as high Young's modulus as the composite based on paper grade kraft pulp, 11-12 and 6 GPa, respectively, and the explanation is most likely the difference in beating response of the pulps. Also the water retention value (WRV) is similarly low for the two molded sulfite pulps (0.5 g/g) as compared to the molded kraft pulp (0.9 g/g). The carbohydrate composition is determined by neutral sugar analysis and average molar masses by SEC. The cellulose supramolecular structure (cellulose fibril aggregation) is studied by solid state CP/MAS 13C-NMR and two forms of hemicellulose are assigned. During compression molding, cellulose fibril aggregation occurs to higher extent in the acid sulfite pulps as compared to the kraft pulp. In conclusion, the most important observation from this study is that the difference in hemicellulose content and structure seems to affect the aggregation behaviour and WRV of the investigated biocomposites.

Keyword
Chemical pulps, Composites, Compression molding, CP/MAS 13C-NMR, Fibril aggregation, Hemicelluloses, Mechanical properties, Aggregation behaviours, Average molar mass, Bio-composites, Content and structure, CP/MAS <sup>13</sup>C-NMR, Material property, Neutral sugar analysis, Paper grade pulp, Softwood Pulps, Supramolecular structure, Water retention value, Wood pulp, Young's Modulus, Chemical pulp, Composite materials, Kraft process, Kraft pulp, Paper and pulp mills, Paper products, Pulp beating, Sugars, Sulfite pulp, Wood, Cellulose, Agglomeration, Sulfite Pulps
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-95695 (URN)10.1007/s10570-012-9688-2 (DOI)000303459200017 ()2-s2.0-84860387690 (Scopus ID)
Note

QC 20150630

Available from: 2012-05-30 Created: 2012-05-29 Last updated: 2017-12-07Bibliographically approved
3. Cellulose nanofibers decorated with magnetic nanoparticles: synthesis, structure and use in magnetized high toughness membranes for a prototype loudspeaker
Open this publication in new window or tab >>Cellulose nanofibers decorated with magnetic nanoparticles: synthesis, structure and use in magnetized high toughness membranes for a prototype loudspeaker
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2013 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, Vol. 1, no 47, p. 7963-7972Article in journal (Refereed) Published
Abstract [en]

Magnetic nanoparticles are the functional component for magnetic membranes, but they are difficult to disperse and process into tough membranes. Here, cellulose nanofibers are decorated with magnetic ferrite nanoparticles formed in situ which ensures a uniform particle distribution, thereby avoiding the traditional mixing stage with the potential risk of particle agglomeration. The attachment of the particles to the nanofibrils is achieved via aqueous in situ hydrolysis of metal precursors onto the fibrils at temperatures below 100 °C. Metal adsorption and precursor quantification were carried out using Induction Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). FE-SEM was used for high resolution characterization of the decorated nanofibers and hybrid membranes, and TEM was used for nanoparticle size distribution studies. The decorated nanofibers form a hydrocolloid. Large (200 mm diameter) hybrid cellulose/ferrite membranes were prepared by simple filtration and drying of the colloidal suspension. The low-density, flexible and permanently magnetized membranes contain as much as 60 wt% uniformly dispersed nanoparticles (thermogravimetric analysis data). Hysteresis magnetization was measured by a Vibrating Sample Magnetometer; the inorganic phase was characterized by XRD. Membrane mechanical properties were measured in uniaxial tension. An ultrathin prototype loudspeaker was made and its acoustic performance in terms of output sound pressure was characterized. A full spectrum of audible frequencies was resolved.

Keyword
Nanocomposite, Magnetic nanoparticle, Cellulose nanofiber, Mechanical properties, Acoustic
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-133562 (URN)10.1039/C3TC31748J (DOI)000327259700024 ()2-s2.0-84887944251 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20131220

Available from: 2013-11-06 Created: 2013-11-06 Last updated: 2013-12-20Bibliographically approved
4. Strong and Moldable Cellulose Magnets with High Ferrite Nanoparticle Content
Open this publication in new window or tab >>Strong and Moldable Cellulose Magnets with High Ferrite Nanoparticle Content
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2014 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 22, p. 20524-20534Article in journal (Refereed) Published
Abstract [en]

A major limitation in the development of highly functional hybrid nanocomposites is brittleness and low tensile strength at high inorganic nanoparticle content. Herein, cellulose nanofibers were extracted from wood and individually decorated with cobalt-ferrite nanoparticles and then for the first time molded at low temperature (<120 degrees C) into magnetic nanocomposites with up to 93 wt % inorganic content. The material structure was characterized by TEM and FE-SEM and mechanically tested as compression molded samples. The obtained porous magnetic sheets were further impregnated with a thermosetting epoxy resin, which improved the load-bearing functions of ferrite and cellulose material. A nanocomposite with 70 wt % ferrite, 20 wt % cellulose nanofibers, and 10 wt % epoxy showed a modulus of 12.6 GPa, a tensile strength of 97 MPa, and a strain at failure of ca. 4%. Magnetic characterization was performed in a vibrating sample magnetometer, which showed that the coercivity was unaffected and that the saturation magnetization was in proportion with the ferrite content. The used ferrite, CoFe2O4 is a magnetically hard material, demonstrated by that the composite material behaved as a traditional permanent magnet. The presented processing route is easily adaptable to prepare millimeter-thick and moldable magnetic objects. This suggests that the processing method has the potential to be scaled-up for industrial use for the preparation of a new subcategory of magnetic, low-cost, and moldable objects based on cellulose nanofibers.

Keyword
cellulose nanofiber, ferrite nanoparticle, nanocomposite, compression-molding, mechanical properties
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-133567 (URN)10.1021/am506134k (DOI)000345721400130 ()25331121 (PubMedID)2-s2.0-84914674971 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20150116

Available from: 2013-11-06 Created: 2013-11-06 Last updated: 2017-12-06Bibliographically approved
5. Cellulose nanofiber network of high specific surface area provides altered curing reacion and moisture stability in ductile epoxy biocomposites
Open this publication in new window or tab >>Cellulose nanofiber network of high specific surface area provides altered curing reacion and moisture stability in ductile epoxy biocomposites
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-133568 (URN)
Note

QS 2013

Available from: 2013-11-06 Created: 2013-11-06 Last updated: 2013-11-11Bibliographically approved
6. UV-cured cellulose nanofiber composites with moisture durable oxygen barrier properties
Open this publication in new window or tab >>UV-cured cellulose nanofiber composites with moisture durable oxygen barrier properties
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-133839 (URN)
Note

QS 2013

Available from: 2013-11-11 Created: 2013-11-11 Last updated: 2013-11-11Bibliographically approved

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