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Eco-friendly Holocellulose Materials for Mechanical Performance and Optical Transmittance
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH Royal institute of technology.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cellulosic materials can be sustainable replacements for fossil-based plastics; yet for some applications improvements are needed for mechanical properties, optical transmittance and eco-friendly characteristics. In this thesis, holocellulose materials are investigated for this purpose, and processing-structure-property relationships are discussed. Molded fibers, without added polymer binder, is of particular interest for semi-structural applications, where facile recycling is possible with highly preserved fiber properties.

Mild delignification is carried out to obtain ramie fibers, spruce holocellulose fibers and holocellulose nanofibrils. The chemical composition, molar mass, crystallinity, fiber length/width, and single fiber strength are measured. Fibers and fibrils show well-preserved native structure. Using water-based hot-pressing, fibers and fibrils are processed into different fiber network materials, including paper structures of 50% porosity, high density molded fibers, and high density nanopaper films. Biocomposites are obtained through methyl methacrylate impregnation and polymerization with molded fibers as reinforcing networks. Fiber orientation is quantified using 2D X-ray diffraction, mechanical properties are determined by tensile testing, and optical properties are measured by transmittance/haze tests in an integrating sphere. Holocellulose materials show much superior mechanical properties and optical transmittance to comparable materials based on industrially available kraft fiber grades. Strong effects from micro-, nano- and molecular scale structures are observed and discussed.

The colloidal stability, redispersibility, and surface modification of holocellulose nanofibrils, as well as recycling and 3D-shaping performance of paper-like structures are investigated. Eco-friendly characteristics include high fiber yield, reduced need for chemical modification and excellent recycling performance with reduced embodied energy in the final material. The enhanced performance of holocellulose materials, compared with materials from kraft fibers, are related to the effects of well-preserved cellulose and hemicellulose structures, as well as structural homogeneity at both molecular, nanofibril and fiber length scales.

Abstract [sv]

Cellulosa-baserade material från förnyelsebar råvara kan fungera som ersättning för fossilbaserade plaster. Den utvecklingen skulle underlättas av förbättrade mekaniska egenskaper, optisk transparens och förbättrad miljövänlig profil (återvinning, koldioxidutsläpp, energiåtgång). Material från holocellulosa analyseras, och relationer mellan process, struktur och egenskaper diskuteras.

Mild delignifiering används för att framställa ramie-fibrer, holocellulosa-fibrer från gran och nanofibriller från holocellulosa. Kemisk sammansättning, molekylvikt, kristallinitet, fiberlängd och diameter, och hållfasthet hos enskilda fibrer studeras. Med hjälp av formpressning, framställs olika typer av material baserade på fibernätverk. Det innefattar pappers-strukturer med 50% porositet, formpressade fibrer, och nanopapper. Biokompositer framställs genom impregnering med metylmetakrylat och polymerisering i närvaro av ett förstärkande nätverk av holocellulosa-fibrer.

Fiberorientering kvantifieras med 2D röntgenspridning, mekaniska egenskaper mäts genom enaxliga dragprov och optiska egenskaper mäts genom att använda en integrerande sfär. Material från holocellulosa har mycket bättre egenskaper än motsvarande material baserade på blekta fibrer från kraft-processen. Starka effekter från struktur på molekylär, nano och mikroskala diskuteras och analyseras i arbetet.

För nanofibriller från holocellulosa undersöks kolloidal stabilitet, återdispergering, ytmodifiering och dessutom återvinning och tredimensionell formning av pappersliknande strukturer. Miljövänliga attribut inkluderar högt fiberutbyte, minskat behov av kemisk modifiering och mycket goda återvinnings-prestanda. Förbättrad prestanda hos holocellulosa-material jämfört med kraft-fibrer, beror på effekter från välbevarad cellulosa, och hemicellulosa, liksom strukturell homogenitet på molekylär, nano och fiberskala.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. , p. 73
Series
TRITA-CBH-FOU ; 2019:60
National Category
Paper, Pulp and Fiber Technology Materials Engineering Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-262895ISBN: 978-91-7873-351-4 (print)OAI: oai:DiVA.org:kth-262895DiVA, id: diva2:1364953
Public defence
2019-11-19, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 2019-10-23

Available from: 2019-10-23 Created: 2019-10-23 Last updated: 2019-10-23Bibliographically approved
List of papers
1. Water-Based Approach to High-Strength All-Cellulose Material with Optical Transparency
Open this publication in new window or tab >>Water-Based Approach to High-Strength All-Cellulose Material with Optical Transparency
2018 (English)In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 6, no 1, p. 501-510Article in journal (Refereed) Published
Abstract [en]

All-cellulose composites are usually prepared by a partial cellulose dissolution approach, using of ionic liquids or organic solvents. Here, an all-cellulose film based on moist ramie fibers was prepared by hot-pressing. The original ramie fiber was degummed, alkali treated, aligned, and mounted into a specially designed mold. The wet ramie fiber "cake" was pressed into a transparent film. The structure, mechanical properties, moisture sorption, and optical properties of the films were investigated using scanning electron microscopy (SEM), X-ray diffraction, tensile tests, gravimetric method, and integrating sphere devices. The all-cellulose films showed an ultimate strength of 620 MPa and a Young's modulus of 39.7 GPa with low moisture sorption and optical transmittance of 85%. These eco-friendly all-cellulose films are of interest for laminated composites, as coatings and in photonics applications.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
Ramie, All-cellulose composite, Compression molding, Mechanical strength, Interface, High transparency, Low moisture sorption
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-221958 (URN)10.1021/acssuschemeng.7b02755 (DOI)000419536800053 ()2-s2.0-85040046287 (Scopus ID)
Note

QC 20180130

Available from: 2018-01-30 Created: 2018-01-30 Last updated: 2019-10-23Bibliographically approved
2. Recycling without Fiber Degradation: Strong Paper Structures for 3D Forming Based on Nanostructurally Tailored Wood Holocellulose Fibers
Open this publication in new window or tab >>Recycling without Fiber Degradation: Strong Paper Structures for 3D Forming Based on Nanostructurally Tailored Wood Holocellulose Fibers
(English)Manuscript (preprint) (Other academic)
National Category
Paper, Pulp and Fiber Technology Materials Engineering
Identifiers
urn:nbn:se:kth:diva-262839 (URN)
Note

QC 20191023

Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2019-10-23Bibliographically approved
3. Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency
Open this publication in new window or tab >>Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency
2018 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 7, p. 3020-3029Article in journal (Refereed) Published
Abstract [en]

To expand the use of renewable materials, paper products with superior mechanical and optical properties are needed. Although beating, bleaching, and additives are known to improve industrially produced Kraft pulp papers, properties are limited by the quality of the fibers. While the use of nanocellulose has been shown to significantly increase paper properties, the current cost associated with their production has limited their industrial relevance. Here, using a simple mild peracetic acid (PAA) delignification process on spruce, we produce hemicellulose-rich holocellulose fibers (28.8 wt %) with high intrinsic strength (1200 MPa for fibers with microfibrillar angle smaller than 10 degrees). We show that PAA treatment causes less cellulose/hemicellulose degradation and better preserves cellulose nanostructure in comparison to conventional Kraft pulping. High-density holocellulose papers with superior mechanical properties (Young's modulus of 18 GPa and ultimate strength of 195 MPa) are manufactured using a water-based hot-pressing process, without the use of beating or additives. We propose that the preserved hemicelluloses act as "glue" in the interfiber region, improving both mechanical and optical properties of papers. Holocellulose fibers may be affordable and applicable candidates for making special paper/composites where high mechanical performance and/or optical transmittance are of interest.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Biochemistry and Molecular Biology Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-232789 (URN)10.1021/acs.biomac.8b00585 (DOI)000438470800065 ()29757614 (PubMedID)2-s2.0-85047085277 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180803

Available from: 2018-08-03 Created: 2018-08-03 Last updated: 2019-10-23Bibliographically approved
4. High-Density Molded Cellulose Fibers and Transparent Biocomposites Based on Oriented Holocellulose
Open this publication in new window or tab >>High-Density Molded Cellulose Fibers and Transparent Biocomposites Based on Oriented Holocellulose
2019 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 10, p. 10310-10319Article in journal (Refereed) Published
Abstract [en]

Ecofriendly materials based on well-preserved and nanostructured wood cellulose fibers are investigated for the purpose of load-bearing applications, where optical transmittance may be advantageous. Wood fibers are subjected to mild delignification, flow orientation, and hot-pressing to form an oriented material of low porosity. The biopolymer composition of the fibers is determined. Their morphology is studied by scanning electron microscopy, cellulose orientation is quantified by X-ray diffraction, and the effect of beating is investigated. Hot-pressed networks are impregnated by a methyl methacrylate monomer and polymerized to form thermoplastic wood fiber/poly(methyl methacrylate) biocomposites. Tensile tests are performed, as well as optical transmittance measurements. Structure-property relationships are discussed. High-density molded fibers from holocellulose have mechanical properties comparable with nanocellulose materials and are recyclable. The thermoplastic matrix biocomposites showed superior mechanical properties (Young's modulus of 20 GPa and ultimate strength of 310 MPa) at a fiber volume fraction of 52%, with high optical transmittance of 90%. The study presents a scalable approach for strong, stiff, and transparent molded fibers/biocomposites.Ecofriendly materials based on well-preserved and nanostructured wood cellulose fibers are investigated for the purpose of load-bearing applications, where optical transmittance may be advantageous. Wood fibers are subjected to mild delignification, flow orientation, and hot-pressing to form an oriented material of low porosity. The biopolymer composition of the fibers is determined. Their morphology is studied by scanning electron microscopy, cellulose orientation is quantified by X-ray diffraction, and the effect of beating is investigated. Hot-pressed networks are impregnated by a methyl methacrylate monomer and polymerized to form thermoplastic wood fiber/poly(methyl methacrylate) biocomposites. Tensile tests are performed, as well as optical transmittance measurements. Structure-property relationships are discussed. High-density molded fibers from holocellulose have mechanical properties comparable with nanocellulose materials and are recyclable. The thermoplastic matrix biocomposites showed superior mechanical properties (Young's modulus of 20 GPa and ultimate strength of 310 MPa) at a fiber volume fraction of 52%, with high optical transmittance of 90%. The study presents a scalable approach for strong, stiff, and transparent molded fibers/biocomposites.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
Keywords
wood, nanocellulose, high strength, modulus, PMMA, interface
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-248343 (URN)10.1021/acsami.8b22134 (DOI)000461538000072 ()30762342 (PubMedID)2-s2.0-85062458848 (Scopus ID)
Note

QC 20190408

Available from: 2019-04-08 Created: 2019-04-08 Last updated: 2019-10-23Bibliographically approved
5. Eco-Friendly Cellulose Nanofibrils Designed by Nature: Effects from Preserving Native State
Open this publication in new window or tab >>Eco-Friendly Cellulose Nanofibrils Designed by Nature: Effects from Preserving Native State
(English)Manuscript (preprint) (Other academic)
National Category
Materials Engineering Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-262841 (URN)
Note

QC 20191023

Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2019-10-23Bibliographically approved

Open Access in DiVA

The full text will be freely available from 2020-11-19 09:42
Available from 2020-11-19 09:42

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Yang, Xuan

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