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Preparation and characterization of nanoporous cellulose fibres and their use in new material concepts
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The overall objective of the work in this thesis is to better utilize the non-collapsed structure of the delignified wood-fibre cell wall in the preparation of new types of materials.

In order to utilize the fibres in new materials, it is crucial to have a well-defined starting material and to know how it reacts to certain treatments of the fibres. A new robust method for measuring the average pore size of water-swollen fibres-rich in cellulose is presented. This method is based on solid-state NMR, which measures the specific surface area [m2/g] of water-swollen samples, and the fibre saturation point (FSP) method, which measures the pore volume [water mass/solid mass] of a water swollen sample. These results can be combined since they are both recorded on water-swollen fibres in the presence of excess water and neither is based on any assumption of any particular pore geometry. Delignifed wood fibres (chemical pulp fibres) have an open fibrillar structure, with approximately 20 nm thick fibril aggregates arranged in a porous structure with a specific surface area of 150 m2/g. This open structure was preserved in the dry state by a liquid-exchange procedure followed by careful drying in argon gas. The dry structure had a specific surface area of 130 m2/g, which implies that the porous structure was preserved in the dry state.

New fibre-basedmaterials were prepared by two different strategies.

The first strategy was to utilize the open nanoporous fibre wall structure for the preparation of nanocomposites. The nanoporous structure was used as a scaffold, allowing monomers to impregnate the structure and to be in-situ polymerized inside the fibre wall pores. Poly(methyl methacrylate) (PMMA) and poly(butylacrylate) (PBA) were synthesized inside the dry nanoporous fibre wall structure, and an epoxy resin was cured in never-dried fibres oxidized to different degrees by TEMPO. The composites prepared thus have a mixture of fibril aggregates and a polymer matrix inside the fibre wall. The structure and performance of the composite materials were evaluated both by high resolution microscopy and mechanically. Characterization of the composite showed that the polymer matrix was successfully formed inside the fibre wall pores. The structural changes caused by oxidation were preserved and utilized for the composite with the epoxy matrix. By tailoring the supramolecular structure of fibres in their water-swollen state, it was hence indeed possible to control the mechanical performance of the nanostructured fibre composites.

The secondbstrategy used to prepare composites was to improve the thermoplastic properties of paper by adding polylactic acid (PLA) latex during the preparation of fibrebsheets. By the addition of PLA-latex, it was possible to form double curved sheets with a nominal strain at break of 21%.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. , 57 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:41
National Category
Paper, Pulp and Fiber Technology Composite Science and Engineering
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-155530ISBN: 978-91-7595-290-1 (print)OAI: oai:DiVA.org:kth-155530DiVA: diva2:761478
Public defence
2014-11-28, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20141107

Available from: 2014-11-07 Created: 2014-11-06 Last updated: 2014-11-07Bibliographically approved
List of papers
1. Preparation of dry ultra-porous cellulosic fibres: Characterization and possible initial uses
Open this publication in new window or tab >>Preparation of dry ultra-porous cellulosic fibres: Characterization and possible initial uses
2013 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 92, no 1, 775-783 p.Article in journal (Refereed) Published
Abstract [en]

Dry ultra-porous cellulose fibres were obtained using a liquid exchange procedure in which water was replaced in the following order: water, methanol, acetone, and finally pentane: thereafter, the fibres were dried with Ar(g). The dry samples (of TEMPO-oxidized dissolving pulp) had a specific surface area of 130 m(2) g(-1) as measured using BET nitrogen gas adsorption. The open structure in the dry state was also revealed using field emission scanning electron microscopy. This dry open structure was used as a scaffold for in situ polymerization. Both poly(methyl methacrylate) and poly(butylacrylate) were successfully used as matrix polymers for the composite material (fibre/polymer), comprising approximately 20 wt% fibres. Atomic force microscopy phase imaging indicated a nanoscale mixing of the matrix polymer and the cellulose fibril aggregates and this was also supported by mechanical testing of the prepared composite where the open fibre structure produced superior composites. The fibre/polymer composite had a significantly reduced water absorption capacity also indicating an efficient filling of the fibre structure with the matrix polymer.

Keyword
Cellulose fibre, Composite, In situ polymerization, Liquid exchange, Open structure, Surface area
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-103402 (URN)10.1016/j.carbpol.2012.09.090 (DOI)000313146900110 ()2-s2.0-84868215766 (Scopus ID)
Note

QC 20130218. Updated from submitted to published.

Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2017-12-07Bibliographically approved
2. A new, robust method for measuring average fibre wall pore sizes in cellulose I rich plant fibre walls
Open this publication in new window or tab >>A new, robust method for measuring average fibre wall pore sizes in cellulose I rich plant fibre walls
2013 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 2, 623-631 p.Article in journal (Refereed) Published
Abstract [en]

A new, robust method for measuring the average pore size of water-swollen, cellulose I rich fibres is presented. This method is based on the results of solid-state NMR, which measures the specific surface area (area/solids mass) of water-swollen samples, and of the fibre saturation point (FSP) method, which measures the pore volume (water mass/solids mass) of water-swollen samples. These results are suitable to combine since they are both recorded on water-swollen fibres in excess water, and neither requires the assumption of any particular pore geometry. The new method was used for three model samples and reasonable average pore size measurements were obtained for all of them. The structural characterization of water-swollen samples was compared with the dry structure of fibres as revealed using BET nitrogen gas adsorption after a liquid exchange procedure and careful drying. It was concluded that the structure of the water-swollen fibres sets an upper limit on what is obtainable in the dry state.

Keyword
Cellulose I, CP/MAS 13C-NMR, Fibre saturation point (FSP), Water retention value (WRV), BET, Pore size
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-103403 (URN)10.1007/s10570-012-9850-x (DOI)000315480400005 ()2-s2.0-84874521408 (Scopus ID)
Note

QC 20130402

Available from: 2012-10-11 Created: 2012-10-11 Last updated: 2017-12-07Bibliographically approved
3. Structural changes during swelling of highly charged cellulose fibres
Open this publication in new window or tab >>Structural changes during swelling of highly charged cellulose fibres
2015 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 5, 2943-2953 p.Article in journal (Refereed) Published
Abstract [en]

Structural changes of fibrils and fibril aggregates in the fibre wall were studied after oxidation of the cellulose by 2,2,6,6-tetramethyl-1-piperidinyloxy to high charge densities (highest charge density: 1300 mu eq/g). The increase in pore volume was measured by mini-WRV at two different pH levels, and the supramolecular structure in the fibre wall in terms of aggregate size, specific surface area and average pore size was measured by solid state NMR, DVS desorption and BET N-2 gas adsorption. A structural change in the arrangement of the fibrils inside the fibril aggregates was observed although the oxidation did not lead to a complete liberation of individual fibrils, i.e. they still exist as an aggregated structure after oxidation. Theoretical estimates suggest that the electrostatic repulsion energy connected with the increase in surface charge of the fibrils can be sufficient to gradually separate the fibrils enough to expose all fibril surfaces to oxidation chemicals.

National Category
Polymer Technologies Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-155537 (URN)10.1007/s10570-015-0701-4 (DOI)000361002000007 ()2-s2.0-84941416963 (Scopus ID)
Note

Updated from manuscript to article.

QC 20151009

Available from: 2014-11-07 Created: 2014-11-07 Last updated: 2017-12-05Bibliographically approved
4. Biocomposites based on nanostructured chemical wood pulp fibres in epoxy matrix
Open this publication in new window or tab >>Biocomposites based on nanostructured chemical wood pulp fibres in epoxy matrix
(English)Manuscript (preprint) (Other academic)
Identifiers
urn:nbn:se:kth:diva-155543 (URN)
Note

QS 2014

Available from: 2014-11-07 Created: 2014-11-07 Last updated: 2014-11-07Bibliographically approved
5. 3D-shapeable thermoplastic paper materials
Open this publication in new window or tab >>3D-shapeable thermoplastic paper materials
2013 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 4, 602-610 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of this work was to investigate to what extent it is possible to improve the thermoplastic properties of paper materials so that 3D-shapeable paper products can be manufactured. For that purpose, the addition of various chemical adjuvants, known to improve both tensile strength index and strain at break, was investigated. Adding polylactide latex was found to significantly improve both the tensile strength properties and strain at break of paper materials. To enhance their strainability, the paper sheets were cured at an elevated temperature of 150 degrees C. The improved strainability after curing is hypothesized to relate to the spreading of the polylactide latex (minimum film-forming temperature of 90 degrees C) on the fibre surfaces, improving the relative bonded area. Both the tensile strength index and strain at break improved significantly with no densification of the paper sheets. A second aim was to make double-curved board structures in a hydroforming equipment, using the sheets treated with polylactide latex under various conditions. Double-curved sheets with a nominal strain at break of over 20% could be formed by adding 20% polylactide latex. Hydroforming had to be done at temperatures exceeding the minimum film-forming temperature of the polylactide latex to significantly improve the strain at break during the forming operation.

Keyword
Deep-drawing, Hydroforming, Thermoplastic board, Polylactide latex, Bleached kraft pulp, Three-dimensional packaging materials, Tensile index, Strain at break
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-140183 (URN)10.3183/NPPRJ-2013-28-04-p602-610 (DOI)000328642400016 ()2-s2.0-84891841593 (Scopus ID)
Note

QC 20140117

Available from: 2014-01-17 Created: 2014-01-17 Last updated: 2017-12-06Bibliographically approved

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