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Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
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2007 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 6, 1934-1941 p.Article in journal (Refereed) Published
Abstract [en]

Toward exploiting the attractive mechanical properties of cellulose I nanoelements, a novel route is demonstrated, which combines enzymatic hydrolysis and mechanical shearing. Previously, an aggressive acid hydrolysis and sonication of cellulose I containing fibers was shown to lead to a network of weakly hydrogen-bonded rodlike cellulose elements typically with a low aspect ratio. On the other hand, high mechanical shearing resulted in longer and entangled nanoscale cellulose elements leading to stronger networks and gels. Nevertheless, a widespread use of the latter concept has been hindered because of lack of feasible methods of preparation, suggesting a combination of mild hydrolysis and shearing to disintegrate cellulose I containing fibers into high aspect ratio cellulose I nanoscale elements. In this work, mild enzymatic hydrolysis has been introduced and combined with mechanical shearing and a high-pressure homogenization, leading to a controlled fibrillation down to nanoscale and a network of long and highly entangled cellulose I elements. The resulting strong aqueous gels exhibit more than 5 orders of magnitude tunable storage modulus G' upon changing the concentration. Cryotransmission electron microscopy, atomic force microscopy, and cross-polarization/magic-angle spinning (CP/MAS) C-13 NMR suggest that the cellulose I structural elements obtained are dominated by two fractions, one with lateral dimension of 5-6 nm and one with lateral dimensions of about 10-20 nm. The thicker diameter regions may act as the junction zones for the networks. The resulting material will herein be referred to as MFC (microfibrillated cellulose). Dynamical rheology showed that the aqueous suspensions behaved as gels in the whole investigated concentration range 0.125-5.9% w/w, G' ranging from 1.5 Pa to 10(5) Pa. The maximum G' was high, about 2 orders of magnitude larger than typically observed for the corresponding nonentangled low aspect ratio cellulose I gels, and G' scales with concentration with the power of approximately three. The described preparation method of MFC allows control over the final properties that opens novel applications in materials science, for example, as reinforcement in composites and as templates for surface modification.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2007. Vol. 8, no 6, 1934-1941 p.
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-37114DOI: 10.1021/bm061215pISI: 000247107900023PubMedID: 17474776OAI: oai:DiVA.org:kth-37114DiVA: diva2:432150
Note

QC 20110801

Available from: 2011-08-01 Created: 2011-08-01 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Microfibrillated cellulose: Energy-efficient preparation techniques and key properties
Open this publication in new window or tab >>Microfibrillated cellulose: Energy-efficient preparation techniques and key properties
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This work describes three alternative processes for producing microfibrillated cellulose (MFC) in which pulp fibres are first pre-treated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated with a combined enzymatic and mechanical pre-treatment. In the two other processes, cell wall delamination was facilitated by pre-treatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethyl cellulose (CMC) onto the fibres. All three processes are industrially feasible and enable production with low energy consumption. Using these methods, MFC can be produced with an energy consumption of 500–2300 kWh/tonne, which corresponds to a 91–98% reduction in energy consumption from that presented in earlier studies. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 49 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 38
Keyword
Microfibrillated cellulose, microfibrillar cellulose, nanofibrillated cellulose nanofibrillar cellulose, nanocellulose, MFC, NFC, production techniques, energy efficient, gel properties, films, enzymes, carboxymethylation, carboxymethyl cellulose, CMC, mechanical properties, oxygen barrier, homogenization
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-102949 (URN)978-91-7501-464-7 (ISBN)
Presentation
2012-10-17, STFI-salen, Innventia AB, Drottning Kristinas väg 61, KTH, Stockholm, 14:02 (Swedish)
Opponent
Supervisors
Note

QC 20120928

Available from: 2012-09-28 Created: 2012-09-28 Last updated: 2012-10-03Bibliographically approved
2. Microfibrillated cellulose: Energy-efficient preparation techniques and applications in paper
Open this publication in new window or tab >>Microfibrillated cellulose: Energy-efficient preparation techniques and applications in paper
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This work describes three alternative processes for producing microfibrillated cellulose (MFC; also referred to as cellulose nanofibrils, CNF) in which bleached pulp fibres are first pretreated and then homogenized using a high-pressure homogenizer. In one process, fibre cell wall delamination was facilitated by a combined enzymatic and mechanical pretreatment. In the two other processes, cell wall delamination was facilitated by pretreatments that introduced anionically charged groups into the fibre wall, by means of either a carboxymethylation reaction or irreversibly attaching carboxymethylcellulose (CMC) to the fibres. All three processes are industrially feasible and enable energy-efficient production of MFC. Using these processes, MFC can be produced with an energy consumption of 500–2300 kWh/tonne. These materials have been characterized in various ways and it has been demonstrated that the produced MFCs are approximately 5–30 nm wide and up to several microns long.

The MFCs were also evaluated in a number of applications in paper. The carboxymethylated MFC was used to prepare strong free-standing barrier films and to coat wood-containing papers to improve the surface strength and reduce the linting propensity of the papers. MFC, produced with an enzymatic pretreatment, was also produced at pilot scale and was studied in a pilot-scale paper making trial as a strength agent added at the wet-end for highly filled papers.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. 63 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2015:5
Keyword
Microfibrillated cellulose, microfibrillar cellulose, nanofibrillated cellulose, nanofibrillar cellulose, cellulose nanofibrils, nanocellulose, MFC, NFC, CNF, production techniques, energy efficient, gel properties, films, enzymes, carboxymethylation, carboxymethyl cellulose, CMC, mechanical properties, oxygen barrier, homogenization, linting, papermaking
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-159222 (URN)978-91-7595-426-4 (ISBN)
Public defence
2015-02-27, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
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Supervisors
Note

QC 20150126

Available from: 2015-01-26 Created: 2015-01-26 Last updated: 2015-01-28Bibliographically approved

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