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Chemical Modification of Cellulose Fibres and Fibrils for Design of New Materials
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology. (Fibre Technology)ORCID iD: 0000-0002-5286-333X
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Due to the growing interest in biobased materials in today’s society, where the need for a cyclic economy is obvious, there has been a huge increase in the  interest for using cellulose due to its excellent mechanical and chemical properties. However, the properties of cellulose have to be modified and improved in order to satisfy advanced material applications where the cellulose properties can be tuned to fit the properties of other components in composite mixtures. This thesis explores the heterogeneous chemical modification of cellulose for improved material properties of cellulose-based materials and the use of cellulose fibres and fibrils in novel applications.

In the first part of the work described in this thesis, a fundamental study was performed to clarify how the chemical composition and the fibre/fibril structure of the cellulose following chemical modification affect the material properties. The second part of the work was aimed at exploring the potential for using the chemically modified fibres/fibrils in novel material applications. 

Lignocellulosic fibres with different chemical compositions were modified by periodate oxidation and borohydride reduction, and it was found that the most important factor was the amount of holocellulose present in the fibres, since lignin-rich fibres were less reactive and less responsive to the treatments. Despite the lower reactivity of lignin-rich fibres, it was however possible to improve their mechanical properties and to achieve a significant increase in the compressive strength of papers prepared from modified unbleached kraft fibres.

The chemical modifications were then expanded to nine different molecular structures and two different degrees of modification. Fibres modified at low degrees of modification were used to prepare handsheets, followed by mechanical and physical characterization. Highly modified fibres were also used to prepare cellulose nanofibrils (CNFs). It was found that the properties of handsheets and films prepared from modified fibres/fibrils are highly dependent on the chemical structure of the modified cellulose and, as an example, the ductility was greatly improved by converting secondary alcohols to primary alcohols. A detailed analysis of the modified fibres and fibrils also showed that, due to the heterogeneous chemical reaction used, the modified fibrils had a core-shell structure with a shell of modified cellulose with a lower crystalline order surrounding a core of crystalline cellulose. The results also showed that the chemical structure of the modified shell dramatically affects the interaction with moisture. Materials from fibrils containing covalent crosslinks have shown to be less sensitive to moisture at the cost of being more brittle. 

In a different application, modified CNFs were used as paper strength additives. Three differently modified CNFs were used: carboxymethylated CNFs, periodate-oxidised carboxymethylated CNFs and dopamine-grafted carboxymethylated CNFs. The properties of these CNFs were compared with that of a microfibrillated cellulose from unbleached kraft fibres. In general, a great improvement in the dry mechanical properties of handsheets was observed with the addition of the periodate-oxidised oxidised and dopamine-grafted modified fibrils, whereas only the periodate-oxidised carboxymethylated CNFs improved the wet strength.

Finally, it was found that the chemically modified fibres could be used to prepare a novel low-density material with good mechanical strength, both wet and dry, and excellent shape recovery capacity in the wet state after mechanical compression. The fibre networks were produced by solvent exchange from water to acetone followed by air drying at room temperature. The properties of the fibre networks could also fairly easily be tuned in terms of porosity, density and strength.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. , p. 68
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2018:1
Keywords [en]
borohydride reduction, cellulose-based materials, chemical modification, chlorite oxidation, fibres, fibrils, periodate oxidation, TEMPO oxidation
National Category
Paper, Pulp and Fiber Technology
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-232090ISBN: 978-91-7729-670-6 (print)OAI: oai:DiVA.org:kth-232090DiVA, id: diva2:1232218
Public defence
2018-02-23, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180711

Available from: 2018-07-11 Created: 2018-07-11 Last updated: 2018-07-11Bibliographically approved
List of papers
1. On the relationship between fibre composition and material properties following periodate oxidation and borohydride reduction of lignocellulosic fibres
Open this publication in new window or tab >>On the relationship between fibre composition and material properties following periodate oxidation and borohydride reduction of lignocellulosic fibres
2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 6, p. 3495-3510Article in journal (Refereed) Published
Abstract [en]

Periodate oxidation followed by borohydride reduction was performed on four structurally different pulp fibres to clarify the effect of chemical composition on the structural and mechanical properties of sheets made from these fibres. The main purpose was to explore the possibility of extending the use of lignocellulose fibres in novel applications. The degree of oxidation, morphological changes, chemical and physical structure of the fibres, the supramolecular ordering of the cellulose and the mechanical performance of handsheets made from the fibres were studied. The results showed that both periodate oxidation and borohydride reduction are more reactive towards the carbohydrates of the fibres and as a result, there is an improvement in the tensile properties of the sheets. If the carbohydrates of the fibres are only periodate oxidised to produce dialdehydes, inter- and intra-fibre crosslinks can be formed, leading to paper with increase strength and higher stiffness. The borohydride reduction results in fibres and papers with a greater strength and ductility. It was also found that the characteristic ductility of these modified papers, emanating from the dialcohol cellulose produced, is limited with lignin-rich fibres.

Place, publisher, year, edition, pages
Springer Netherlands, 2016
Keywords
Borohydride reduction, Dialcohol cellulose, Dialdehyde cellulose, Lignocellulose fibres, Periodate oxidation, Strain-at-break, Tensile strength, Alcohols, Carbohydrates, Cellulose, Crosslinking, Ductility, Fibers, Lignin, Oxidation, Polyols, Borohydride reductions, Mechanical performance, Strain at break, Strength and ductilities, Structural and mechanical properties, Supramolecular ordering
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-194871 (URN)10.1007/s10570-016-1061-4 (DOI)000388961200009 ()2-s2.0-84984923972 (Scopus ID)
Funder
VINNOVA
Note

QC 20161213

Available from: 2016-12-13 Created: 2016-11-01 Last updated: 2018-07-11Bibliographically approved
2. Chemical modification of cellulose-rich fibres to clarify the influence of the chemical structure on the physical and mechanical properties of cellulose fibres and thereof made sheets
Open this publication in new window or tab >>Chemical modification of cellulose-rich fibres to clarify the influence of the chemical structure on the physical and mechanical properties of cellulose fibres and thereof made sheets
2018 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 182, p. 1-7Article in journal (Refereed) Published
Abstract [en]

Despite the different chemical approaches used earlier to increase the ductility of fibre-based materials, it has not been possible to link the chemical modification to their mechanical performance. In this study, cellulose fibres have been modified by periodate oxidation, alone or followed either by borohydride reduction, reductive amination or chlorite oxidation. In addition, TEMPO oxidation, and TEMPO oxidation in combination with periodate oxidation and further reduction with sodium borohydride have also been studied. The objective was to gain understanding of the influence of different functional groups on the mechanical and structural properties of handsheets made from the modified fibres. It was found that the modifications studied improved the tensile strength of the fibres to different extents, but that only periodate oxidation followed by borohydride reduction provided more ductile fibre materials. Changes in density, water-holding capacity and mechanical performance were also quantified and all are dependent on the functional group introduced.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Borohydride reduction, Cellulose fibres, Chemical modification, Chlorite oxidation, Periodate oxidation, Structure-property relationship, TEMPO oxidation
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-218909 (URN)10.1016/j.carbpol.2017.11.006 (DOI)000418661800001 ()2-s2.0-85032914983 (Scopus ID)
Funder
VINNOVA
Note

QC 20171201

Available from: 2017-12-01 Created: 2017-12-01 Last updated: 2018-07-11Bibliographically approved
3. Effect of chemical functionality on the mechanical and barrier performance of all-cellulose composites
Open this publication in new window or tab >>Effect of chemical functionality on the mechanical and barrier performance of all-cellulose composites
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-232099 (URN)
Note

QC 20180711

Available from: 2018-07-11 Created: 2018-07-11 Last updated: 2018-07-11Bibliographically approved
4. Chemically modified cellulose micro- and nanofibrils as paper-strength additives
Open this publication in new window or tab >>Chemically modified cellulose micro- and nanofibrils as paper-strength additives
2017 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 9, p. 3883-3899Article in journal (Refereed) Published
Abstract [en]

Chemically modified cellulose micro- and nanofibrils were successfully used as paper strength additives. Three different kinds of cellulose nanofibrils (CNFs) were studied: carboxymethylated CNFs, periodate-oxidised carboxymethylated CNFs and dopamine-grafted carboxymethylated CNFs, all prepared from bleached chemical fibres of dissolving grade, and one microfibrillated cellulose from unbleached kraft fibres. In addition to mechanical characterization of the final paper sheets the fibril retention, sheet density and sheet morphology were also studied as a function of addition of the four different cellulose fibrils. In general, the cellulose fibrils, when used as additives, significantly increased the tensile strength, Young’s modulus and strain-at-break of the paper sheets. The effects of the different fibrils on these properties were compared and evaluated and used to analyse the underlying mechanisms behind the strengthening effect. The strength-enhancing effect was most pronounced for the periodate-oxidised CNFs when they were added together with polyvinyl amine (PVAm) or poly(dimethyldiallylammonium chloride) (pDADMAC). The addition of periodate-oxidised CNFs, with pDADMAC as retention aid, resulted in a 37% increase in tensile strength at a 2 wt% addition and an 89% increase at a 15 wt% addition (from 67 to 92 and 125 kNm/kg, respectively) compared to a reference with only pDADMAC. Wet-strong sheets with a wet tensile index of 30 kNm/kg were also obtained when periodate-oxidised CNFs and PVAm were combined. This significant increase in wet strength is suggested to be the result of a formation of cross-links between the aldehyde groups, introduced by the periodate oxidation, and hydroxyl groups on the lignocellulosic fibres and the primary amines of PVAm. Even though less significant, there was also an increase in wet tensile strength when pDADMAC was used together with periodate-oxidised fibrils which shows that the aldehyde groups are able to increase the wet strength without the presence of the primary amines of the PVAm. As an alternative method to strengthen the fibre network, carboxymethylated CNFs grafted with dopamine, by an ethyl dimethylaminopropyl carbodiimide coupling, were used as a strength additive. When used as an additive, these CNFs showed a strong propensity to form films on and around the fibres and significantly increased the mechanical properties of the sheets. Their addition resulted in an increase in the Young´s modulus by 41%, from 5.1 to 7.2 GPa, and an increase in the tensile strength index of 98% (from 53 to 105 kNm/kg) with 5 wt% retained dopamine-grafted CNFs.

Place, publisher, year, edition, pages
Springer Netherlands, 2017
Keywords
Carboxymethylation, Cellulose nanofibrils, Dopamine grafting, Paper strength, Periodate oxidation, Strength additives, Additives, Aldehydes, Amines, Cellulose, Fibers, Grafting (chemical), Nanofibers, Neurophysiology, Oxidation, Paper products, Polyvinyl chlorides, Paper strengths, Tensile strength
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-218823 (URN)10.1007/s10570-017-1387-6 (DOI)2-s2.0-85021744663 (Scopus ID)
Note

QC 20180117

Available from: 2018-01-17 Created: 2018-01-17 Last updated: 2018-07-11Bibliographically approved
5. Novel cellulose-based light weight, wet resilient materials with tunable porosity, density and strength
Open this publication in new window or tab >>Novel cellulose-based light weight, wet resilient materials with tunable porosity, density and strength
(English)Manuscript (preprint) (Other academic)
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-232100 (URN)
Note

QC 20180711

Available from: 2018-07-11 Created: 2018-07-11 Last updated: 2018-07-11Bibliographically approved

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