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Manufacturing and Characterization of Cellulose Nanofibers
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.ORCID iD: 0000-0002-8125-7734
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The usage of wood has been a dominant driving force during the evolution of the human species. It allowed us to cook food, build tools, put roofs over our head and explore the world. The fibers making up the tree has been the most important way to store and transmit knowledge in the form of paper for centuries. It may not be considered as the most interesting or hi-tech of fields, although, nothing could be further from the truth. One of society's most significant issue is how to live sustainably, which is coincidentally exactly what trees can solve. We can live in tall buildings made from wood, locking up vast amounts of carbon dioxide - we can replace many of the plastics we use today with sustainable alternative from the components making up the tree - we could even make clothes from our trees and stop being reliant on the untenable cotton production - only our imagination is holding us back from what can be made from trees.

Cellulose is the structural component in trees, the molecule arranges itself in a complex hierarchical structure that forms the wood-cells, or fibers. Breaking down this hierarchical structure down to its smallest structural units leaves us with tiny fibers, no longer than a few micrometers and with a width of merely four nanometers. These are cellulose nanofibers, and this work has aimed to understand how and what it takes to liberate these fine fibers from the larger fiber that they make up. Two main pathways exist to liberate the nanofibers, either chemically by introducing negatively charged groups on the surface of the cellulose, making the fibrils repel each other, or mechanically, simply by intense processing of the fibers. However, these processes are associated with certain flaws in that (i) vast amount of energy is required unless the fibers are pretreated, (ii) disintegration is performed in instruments that do not scale well, (iii) disintegration is carried out at a low concentration of fibers, typically below 5%. Additionally, what comes out of a process is difficult to characterize in terms of quality due to an inherent inhomogeneity and the small size of the nanofibers.

These issues in combination with a greater understanding of the processes are the foundation of this thesis.

Decreased energy consumption and scalability was explored via the steam explosion concept Nanopulp. In order to avoid issues associated with the low concentration, a method was developed for drying cellulose nanofibers to a paste without causing hornification using glycerol. A variety of cellulose nanofibers from different sources were prepared and characterization techniques were compared and expanded upon, including the development of a method for better describing the surface area of cellulose nanofibers. Finally, an environmentally friendly composite was made using cheap and available resources in combination with cellulose nanofibers.

Abstract [sv]

Användningen av träd har varit en viktig del under människans evolution. Dessa har tillåtit oss tillaga mat, tillverka verktyg, bygga hus och utforskavärlden. Fibrerna som ett träd är uppbyggt av har i form av papper varitdet viktigaste sättet att lagra och överföra kunnskap under århundranden. Detta fält betraktas ofta som ganska tråkigt och inte så hi-tech, vilket är långt ifrån sanningen. Ett av samhällets största problemen idag är hur manska leva på ett hållbart sätt, vilket är exakt vad vi kan lösa med hjälp avträd. Vi kan bygga höga byggnader av trä att bo i för att binda upp storamängder koldioxid. Vi kan ersätta många av de plaster vi idag användermed hållbara alternativ från de komponenter som utgör träd. Vi kan till och med göra kläder från våra träd för att sluta vara beroende av den ohållbara bomullsproduktionen - bara fantasin sätter gränser för vad som kan göras frånträd. Cellulosa är den huvudsakligen strukturella komponenten i trä, molekylen ordnar sig i en komplex hierarkisk struktur som bildar träcellerna eller fibrerna. Genom att bryta ner denna hierarkiska strukturen till dess minsta strukturella enhet, småfibrer, som bara är några mikrometer långa och meden bredd av ynka fyra nanometer. Dessa är cellulosa nanofibrer och syftetmed detta arbete har varit att förstå hur och vad som krävs för att frigöra dessa småfibrer från den större fiber som de utgör. Det finns principiellt två vägar att gå för att sönderdela en fiber till nanofibrer, antingen kemiskt genom introduktion av negativt laddade grupper på cellulosans yta, vilket gör att nanofibrerna stöter ifrån varandra, eller mekaniskt, genom intensivt mekanisk bearbetning av fibrerna. Dessa processer är emellertid förknippade med vissa brister i och med att (i) stor mängd energi krävs om inte fibrerna förbehandlas, (ii) delaminering utförs i instrument som inte skalar väl industriellt, (iii) delaminering utförs vid en låg koncentration av fibrer, typiskt under 5%. Dessutom är det svårt att karakterisera det som kommer ut med hänsyn till kvalité på grund av inhomogeniteten och den lilla storleken hos nanofibrerna. Dessa problem i kombination med en större förståelse av processerna är ämnet för denna avhandling. 

Förmindskad energikonsumption och uppskalning undersöktes genom ett ångexplosionskonceptet, Nanopulping. För att undvika problemen associerade med den låga koncentrationen utvecklades en metod för att torka cellulosa nanofibrer till en pasta utan att orsaka hornifiering med hjälp av glycerol. En mängd cellulosa nanofibrer med olika utgångsmaterial framställdes och karaktäriseringstekniker jämfördes och utvecklades, denna utveckling innefattade bland annat en metod för att bättre beskriva ytan av cellulosa nanofibrer. Slutligen tillverkades en miljövänlig komposit från billiga och tillgängliga resurser i kombination med cellulosa nanofibrer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 70
Series
TRITA-CBH-FOU ; 2019:1
Keywords [en]
Cellulose, Nanofibers, Characterization, Homogenization, Endoglucanase, TEMPO, Specific surface area, Atomic force microscopy
Keywords [sv]
Cellulosa, Nanofibrer, Karakterisering, Homogenisering, Endoglukanas, TEMPO, Specifik ytarea, Atomkraftmikroskopi
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-240581ISBN: 978-91-7873-079-7 (print)OAI: oai:DiVA.org:kth-240581DiVA, id: diva2:1272867
Public defence
2019-01-25, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
Knowledge Foundation
Note

QC 20181223

Available from: 2018-12-23 Created: 2018-12-20 Last updated: 2019-01-08Bibliographically approved
List of papers
1. Toward Industrially Feasible Methods for Following the Process of Manufacturing Cellulose Nanofibers
Open this publication in new window or tab >>Toward Industrially Feasible Methods for Following the Process of Manufacturing Cellulose Nanofibers
2015 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 2, p. 2360-2375Article in journal (Refereed) Published
Abstract [en]

Nanocellulose is a recently developed form of cellulose that has the potential to be used in many different industries, ranging from food to high-performance applications. This material is commercially manufactured through the homogenization of chemical pulps, but the process is energy-consuming and is still an important subject for development. Simple, robust methods are required for the quality control and optimization of industrial nanocellulose production. In this study, a number of different methods, based on different principles of monitoring the manufacture of cellulose nanofibers were evaluated and compared for five different nanocellulose qualities, both for their resolution and robustness/ease. Methods based on microscopy, light scattering, centrifugation, and viscosity were examined and all appeared useful for observing the manufacturing process during its initial stage. However, only methods based on centrifugation, turbidity, and transmittance yielded reliable data for the entire manufacturing process. Of these methods, transmittance measurement may be the best candidate for routine use because the method is simple, rapid, and only requires spectrophotometer equipment.

Keywords
Cellulose nanofibers, Microfibrillated cellulose, Nanofibrillated cellulose, Characterization, Transmittance, Turbidity
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-172271 (URN)000354642000034 ()
Note

QC 20150818

Available from: 2015-08-18 Created: 2015-08-14 Last updated: 2018-12-21Bibliographically approved
2. Specific surface area increase during cellulose nanofiber manufacturing related to energy input
Open this publication in new window or tab >>Specific surface area increase during cellulose nanofiber manufacturing related to energy input
2016 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 3, p. 7124-7132Article in journal (Refereed) Published
Abstract [en]

Softwood fibers pretreated with a monocomponent endoglucanase were used to prepare a series of cellulose nanofiber qualities using a microfluidizer and 2 to 34 MWh ton-1 of energy input. The specific surface area was determined for the series using critical point drying and gas adsorption. Although the specific surface area reached a maximum of 430 m2 g-1 at 11 MWh ton-1, the nanofiber yield and transmittance continued to increase beyond this point, indicating that more energy is required to overcome possible friction caused by an interwoven nanofiber network unrelated to the specific surface area. A new method for estimating the surface area was investigated using xyloglucan adsorption in pure water. With this method it was possible to follow the disintegration past the point of maximum specific surface area. The technical significance of these findings is discussed.

Place, publisher, year, edition, pages
North Carolina State University, 2016
Keywords
Cellulose, Cellulose nanofibers, Homogenization, Nano, Specific surface area, Xyloglucan
National Category
Polymer Technologies Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-195543 (URN)10.15376/biores.11.3.7124-7132 (DOI)2-s2.0-84988493706 (Scopus ID)
Note

QC 20161121

Available from: 2016-11-21 Created: 2016-11-03 Last updated: 2018-12-21Bibliographically approved
3. Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation
Open this publication in new window or tab >>Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation
Show others...
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 15, p. 13508-13519Article in journal (Refereed) Published
Abstract [en]

This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
cellulose nanofibers (CNF), comparison, correlation, film, hardwood, softwood, tunicate
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-205365 (URN)10.1021/acsami.7b01738 (DOI)000399965700066 ()28350431 (PubMedID)2-s2.0-85018498856 (Scopus ID)
Note

QC 20170419

Available from: 2017-04-14 Created: 2017-04-14 Last updated: 2018-12-21Bibliographically approved
4. Xyloglucan adsorption for measuring the specific surface area on various never-dried cellulose nanofibers
Open this publication in new window or tab >>Xyloglucan adsorption for measuring the specific surface area on various never-dried cellulose nanofibers
Show others...
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 2, p. 186-193Article in journal (Refereed) Published
Abstract [en]

In this paper, we explore xyloglucan adsorption to cellulose nanofibers as a method for the evaluation of their quality (i. e., the degree of disintegration) and the accessible surface area in the wet state and at low ionic strength. This method was shown to be capable of estimating the surface areas of 14 different cellulose nanofiber qualities from both hardwood and softwood with different pretreatments, including enzymatic hydrolysis using a monocomponent endoglucanase, TEMPO-mediated oxidation, and carboxymethylation. The cellulose surface measured using this method showed a correlation with the degree of disintegration expressed as transmittance for different concentrations of xyloglucan.

Place, publisher, year, edition, pages
Berlin: De Gruyter Open, 2018
Keywords
cellulose, nanofibers, xyloglucan, specific surface area
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-238857 (URN)10.1515/npprj-2018-3034 (DOI)000450922400003 ()2-s2.0-85049499781 (Scopus ID)
Note

QC 20181120

Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-12-21Bibliographically approved
5. Xyloglucan for estimating the surface area of cellulose fibers
Open this publication in new window or tab >>Xyloglucan for estimating the surface area of cellulose fibers
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 2, p. 194-199Article in journal (Refereed) Published
Abstract [en]

The hemicellulose xyloglucan can be utilized to measure exposed cellulose surfaces for pulp fibers. This was shown by correlating a refining series with the adsorbed amount of xyloglucan, and by swelling cellulose fibers to various degrees by increasing the charge density. The method is specific to cellulose and could be used to quantify refining or to determine hornification.

Place, publisher, year, edition, pages
Berlin: De Gruyter Open, 2018
Keywords
cellulose, fibers, specific surface area, softwood, TEMPO, xyloglucan
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-238858 (URN)10.1515/npprj-2018-3035 (DOI)2-s2.0-85049131618& (Scopus ID)
Note

QC 20181120

Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-12-21Bibliographically approved
6. A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration
Open this publication in new window or tab >>A novel nano cellulose preparation method and size fraction by cross flow ultra- filtration
Show others...
2012 (English)In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 16, p. 1871-1875Article in journal (Refereed) Published
Abstract [en]

A novel energy-efficient method called nanopulping (patent pending) to produce nanocellulose from chemical pulp, and a novel cross-flow ultra-filtration method to separate nanofibrils fractions of different size were applied in this study. Pretreatment with endoglucanase or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation seems to enhance the nanopulping process. Results were evaluated with atomic force microscope and ultrafiltration. The nanopulping produced a relatively inhomogeneous material with larger particles/ fibers in addition to nanofibers. However, by ultrafiltration of the material it was possible to obtain more homogeneous material in different dimensions with methods industrially acceptable.

Keywords
Cross flow ultra-filtration, Endoglucanase pretreatment, Microfibrillated cellulose, Nanocellulose, Nanopulping, TEMPO pretreatment
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-101522 (URN)10.2174/138527212802651197 (DOI)000307867800006 ()2-s2.0-84864563327 (Scopus ID)
Note

QC 20120904

Available from: 2012-09-04 Created: 2012-08-30 Last updated: 2018-12-21Bibliographically approved
7. Transparent Composites Made from Tunicate Cellulose Membranes and Environmentally Friendly Polyester
Open this publication in new window or tab >>Transparent Composites Made from Tunicate Cellulose Membranes and Environmentally Friendly Polyester
2018 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 11, no 10, p. 1728-1735Article in journal (Refereed) Published
Abstract [en]

A series of optically transparent composites were made by using tunicate cellulose membranes, in which the naturally organized cellulose microfibrillar network structure of tunicate tunics was preserved and used as the template and a solution of glycerol and citric acid at different molar ratios was used as the matrix. Polymerization through ester bond formation occurred at elevated temperatures without any catalyst, and water was released as the only byproduct. The obtained composites had a uniform and dense structure. Thus, the produced glycerol citrate polyester improved the transparency of the tunicate cellulose membrane while the cellulose membrane provided rigidity and strength to the prepared composite. The interaction between cellulose and polyester afforded the composites high thermal stability. Additionally, the composites were optically transparent and their shape, strength, and flexibility were adjustable by varying the formulation and reaction conditions. These composites of cellulose, glycerol, and citric acid are renewable and biocompatible and have many potential applications as structural materials in packaging, flexible displays, and solar cells.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
carbohydrates, gels, membranes, nanostructures, polymerization
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-231215 (URN)10.1002/cssc.201800627 (DOI)000434216800017 ()29644799 (PubMedID)2-s2.0-85046335513 (Scopus ID)
Note

QC 20180628

Available from: 2018-06-28 Created: 2018-06-28 Last updated: 2018-12-21Bibliographically approved
8. Improved dispersibility of once-dried cellulose nanofibers in the presence of glycerol
Open this publication in new window or tab >>Improved dispersibility of once-dried cellulose nanofibers in the presence of glycerol
2018 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Article in journal (Refereed) Epub ahead of print
Abstract [en]

To investigate the dispersibility of dried cellulose nanofibers (CNFs), various additions (glycerol, octanol, glycol, and sodium perchlorate) were added to CNFs prior to drying. Glycerol was the only species to show any significant effect on re-dispersibility. The sedimentation was slower, and the transmittance of the solution was comparable to that of its undried counterpart. Increasing the amount of glycerol showed a clear trend with regard to dispersibility. The mechanical properties of films were maintained for samples that were dried and redispersed in the presence of glycerol.

Place, publisher, year, edition, pages
Berlin: De Gruyter Open, 2018
Keywords
cellulose nanofibers, CNF, drying, glycerol, hornification, MFC, redispersion
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-238860 (URN)10.1515/npprj-2018-0054 (DOI)000451437900008 ()2-s2.0-85056550081 (Scopus ID)
Note

QC 20181120

Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-12-21Bibliographically approved
9. Structural aspects on the manufacturing of cellulose nanofibers from wood pulp fibers
Open this publication in new window or tab >>Structural aspects on the manufacturing of cellulose nanofibers from wood pulp fibers
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-240625 (URN)
Available from: 2018-12-21 Created: 2018-12-21 Last updated: 2018-12-23

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