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De-watering of Cellulose-based Gel Networks Targeting Different Factors Contributing to the Swelling Pressure
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
RISE Bioeconomy.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. RISE Bioeconomy.ORCID iD: 0000-0001-9176-7116
KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.ORCID iD: 0000-0001-8622-0386
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-250025OAI: oai:DiVA.org:kth-250025DiVA, id: diva2:1306994
Note

QC 20190521

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-05-21Bibliographically approved
In thesis
1. Swelling of Cellulose Fibrillar Matrices and Gels
Open this publication in new window or tab >>Swelling of Cellulose Fibrillar Matrices and Gels
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the major challenges of today´s society is to find a sustainable way to create a living based on the resources on earth. It is a challenge that includes a transition from fossil-based materials to renewable/biodegradable raw materials and also the creation of an environmentally friendly circular material flow. In the search for renewable and biodegradable raw materials, the forest has gained renewed interest. In Sweden, 70 % of the area is covered with forest and, together with a long history of a sustainable forestry, this means that there are environmental and economic gains if this resource is utilized in a correct way and research and development into new wood-based materials has advanced significantly during the last decades. The wood component that has gained the most attention is cellulose and due to the ability of cellulose to act as a light-weight reinforcing component in composites and also due to the variability by which cellulose can be modified in order to obtain a wide range of useful properties. One advantage of cellulose-based materials is that they can be processed in water since the cellulose is hydrophilic and is softened by exposure to water. At the same time, this is one of the major drawbacks of cellulose-based materials since their properties deteriorate when exposed to water, whether as moist air or as condensed liquid. To optimize the use of cellulose fibers/fibrils/gels, knowledge of the effect on the inherent properties of cellulose in contact with water needs to be extended. This project has therefore focused on a fundamental understanding of the reasons behind the water uptake/swelling in a cellulose-rich fiber assembly immersed in water.

The project has included the development and characterization of cellulose model materials in the form of gel (beads) and fibrillar (filaments) networks, for which the swelling was measured as a dimensional change in different aqueous environments. In one of the subprojects, the ion-induced swelling in different cellulose networks was measured on model materials and it was shown that the ion-induced contribution to the swelling was not only dependent on pH and salt concentration in the aqueous solution but also on the stiffness and structure of the network. Thermodynamic models describing gel swelling were used to separate and quantify the osmotic pressure associated with different factors contributing to the total osmotic pressure (ions, mixing and network) of never-dried gel beads. It was thus possible to identify the factor which had a dominant influence in the osmotic pressure and hence most important on the swelling of the systems. Never-dried gel beads showed that the network entropy was the most important factor controlling the swelling of the beads up to a volume fraction of cellulose of 35 %. Above this volume fraction the mixing entropy was found to dominate the swelling. It was also found that the distribution of the total osmotic pressure on these three factors was dependent on the network structure, as the distribution changed when the beads were dried and rewetted compared to the never-dried beads. Finally the de-watering ability of the gel beads in different environments was studied, and also after different modifications targeting the properties shown to have the most dominant effect on the osmotic swelling pressure (ion, mix and network). It was possible to quantify how the gel beads were dewatered to different degrees if e.g. hydrogen was chosen as the counter-ion to the carboxyl groups, if the polarity of the solution was lowered and if the structure of cellulose was changed. This information can, for example, be used to predict how nanocellulose based networks are dewatered under different conditions and this is essential for the preparation of materials based on cellulose nanofibrils.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 68
Series
TRITA-CBH-FOU ; 2019:22
Keywords
swelling, hydrogel, cellulose, wood, cellulose fibrils
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-250026 (URN)978-91-7873-168-8 (ISBN)
Public defence
2019-05-24, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20190425

Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-04-25Bibliographically approved

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Karlsson, Rose-Marie PernillaFall, AndreasLarsson, Per TomasWågberg, Lars

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