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Switchable ionic liquids enable efficient nanofibrillation of wood pulp
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-6247-5963
Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University .
Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University .
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0002-2388-3358
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2017 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 8, p. 3265-3279Article in journal (Refereed) Published
Abstract [en]

Use of switchable ionic liquid (SIL) pulp offers an efficient and greener technology to produce nanofibers via ultrafine grinding. In this study, we demonstrate that SIL pulp opens up a mechanically efficient route to the nanofibrillation of wood pulp, thus providing both a low cost and chemically benign route to the production of cellulose nanofibers. The degree of fibrillation during the process was evaluated by viscosity and optical microscopy of SIL treated, bleached SIL treated and a reference pulp. Furthermore, films were prepared from the fibrillated material for characterization and tensile testing. It was observed that substantially improved mechanical properties were attained as a result of the grinding process, thus signifying nanofibrillation. Both SIL treated and bleached SIL treated pulps were fibrillated into nanofibers with fiber diameters below 15 nm thus forming networks of hydrophilic nature with an intact crystalline structure. Notably, it was found that the SIL pulp could be fibrillated more efficiently than traditional pulp since nanofibers could be produced with more than 30% less energy when compared to the reference pulp. Additionally, bleaching reduced the energy demand by further 16%. The study demonstrated that this switchable ionic liquid treatment has considerable potential in the commercial production of nanofibers due to the increased efficiency in fibrillation.

Place, publisher, year, edition, pages
Springer, 2017. Vol. 24, no 8, p. 3265-3279
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
URN: urn:nbn:se:ltu:diva-63803DOI: 10.1007/s10570-017-1354-2ISI: 000405612000013Scopus ID: 2-s2.0-85020247731OAI: oai:DiVA.org:ltu-63803DiVA, id: diva2:1106930
Note

Validerad;2017;Nivå 2;2017-08-10 (rokbeg)

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2019-09-19Bibliographically approved
In thesis
1. From bio-based residues to nanofibers using mechanical fibrillation for functional biomaterials
Open this publication in new window or tab >>From bio-based residues to nanofibers using mechanical fibrillation for functional biomaterials
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Från biobaserade restprodukter till nanofibrer genom mekanisk fibrillering för funktionella material
Abstract [en]

Bio-based resource utilization in different forms has been driven by societal, industrial and academic research interests towards the development of “green”, sustainable materials from renewable sources. Within this context, exploiting biomass from different industrial residues is further advantageous from an environmental and economic point of view, leading to minimization of residues by means of waste treatment and to the development of high-addedvalue- products. Breaking down the cell wall structure to its smallest structural components is one means of turning bio-based residues into high-value products, leaving us with nanofibers. The aim of this work has been to understand how these nanofibers can be liberated from various cellulosic sources using mechanical fibrillation and how they can be assembled into functional hydrogels.

The production of bio-based nanofibers as a sustainable bio-based material is in the early stages of commercialization and considerable research has been devoted to explore different methods of reaching nanoscale. However, the extraction process by chemical and/or mechanical means is still associated with a relatively high energy demand and/or cost. These are key obstacles for use of the material in a wide range of applications. Another challenge is that methods to characterize nanofiber dimensions are still being developed, with few options available as online measurements for assessing the degree of fibrillation. Allowing for assessment during the fibrillation process would enable not only optimization towards a more energy efficient fibrillation, but also matching of the nanofiber quality to its intended function, since different applications will require widely different nanofiber qualities. Energy-efficient fibrillation and scalability from industrial residues were explored using upscalable ultrafine grinding processes.

Nanofibers from various industrial bio-residues and wood were prepared and characterized, including the development of a method for evaluation of the fibrillation process online via viscosity measurements as an indication of the degree of fibrillation down to nanoscale. Furthermore, the correlation of viscosity to that of the strength of the nanopapers (dried fiber networks) was evaluated for the different raw materials.

Switchable ionic liquids (SIL) were tested as a green pretreatment for delignification, without bleaching of wood prior to fibrillation, with the aim to preserve the low environmental impact that the raw material source offers.

In order to employ the hydrophilic nature and strong network formation ability of the fibrillated nanofibers, they were utilized in the preparation of functional biomaterials in the form of hydrogels. Firstly, brewer’s spent grain nanofibers were used to promote and reinforce hydrogel formation of lignin-containing arabinoxylan, resulting in a hydrogel completely derived from barley residues. In addition, alginate-rich seaweed nanofibers from the stipe (stem-like part of the seaweed) were used directly after fibrillation as an ink and hydrogels were formed via 3D printing.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
Nanofibers, Industrial residues, Ultrafine grinding, Energy-efficiency, Network formation, Hydrogel
National Category
Materials Engineering Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-76015 (URN)978-91-7790-444-1 (ISBN)978-91-7790-445-8 (ISBN)
Public defence
2019-11-15, E632, Luleå tekniska universitet, 97187 Luleå, Luleå, 10:00 (English)
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Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-10-22Bibliographically approved

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Berglund, LinnAitomäki, YvonneOksman, Kristiina

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