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Wood Nanotechnologies for Transparency, Fire Retardancy and Liquid Separation
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH). (Biocomposites)
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, wood nanotechnologies for transparent, fire-retardant and hydrophobic/lipophilic wood have been developed. There are two main parts; wood template preparation/processing concepts and materials design using these templates.

In the wood template processing part, highly porous nanostructured wood templates are prepared. Relationships between processes and material structures are studied. Three chemical treatment methods are used. Lignin and/or chromophores are removed from cell wall, so that nanoscale pores are formed in the cell wall. For preparation of transparent wood, a lignin-retaining method improves physical properties of the template. The pore structures are characterized by scanning electron microscopy and gas adsorption measurement of specific surface area. The compositions of the templates are characterized. Compared with native wood, these templates have nanoscale porosity which provides opportunity for new types of wood modification.

In the materials design part, wood nanotechnologies are used for transparent wood as well as for hydrophobic/lipophilic and fire-retardant wood. Two main strategies are used: i) nanoparticles are embedded inside the cell wall; ii) polymers are impregnated in lumen space, and sometimes also inside the cell wall. The transparent wood is prepared by MMA monomer/oligomer impregnation of lumen space. MMA has similar refractive index to the delignified template, so that scattering is reduced and transparent wood with favorable optical and mechanical properties is obtained. The structure and functional properties are studied. Laminated transparent plywood is designed to modify mechanical properties. Transparent wood and transparent plywood are demonstrated in applications combining loading-bearing properties with optical performance such as luminescent properties.

The highly porous wood template cell walls are also impregnated with colloidal montmorillonite clay or epoxy/amine solutions to modify the cell wall and form nanostructured biocomposites. The structure and properties of the two materials are investigated; wood/clay hybrids for flame-retardancy and wood/epoxy biocomposites for oil/water separation.

Place, publisher, year, edition, pages
Stockholm: Royal Institute of Technology , 2018. , p. 77
Series
TRITA-CBH-FOU ; 2018:1
National Category
Engineering and Technology
Research subject
Materials Science and Engineering; Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-223441ISBN: 978-91-7729-671-3 (electronic)OAI: oai:DiVA.org:kth-223441DiVA, id: diva2:1184451
Public defence
2018-03-07, F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180221

Available from: 2018-02-21 Created: 2018-02-21 Last updated: 2018-05-31Bibliographically approved
List of papers
1. Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance
Open this publication in new window or tab >>Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance
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2016 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 4, p. 1358-1364Article in journal (Refereed) Published
Abstract [en]

Optically transparent wood (TW) with transmittance as high as 85% and haze of 71% was obtained using a delignified nanoporous wood template. The template was prepared by removing the light-absorbing lignin component, creating nanoporosity in the wood cell wall. Transparent wood was prepared by successful impregnation of lumen and the nanoscale cellulose fiber network in the cell wall with refractive-index-matched prepolymerized methyl methacrylate (MMA). During the process, the hierarchical wood structure was preserved. Optical properties of TW are tunable by changing the cellulose volume fraction. The synergy between wood and PMMA was observed for mechanical properties. Lightweight and strong transparent wood is a potential candidate for lightweight low-cost, light-transmitting buildings and transparent solar cell windows.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keyword
Solar-Cells, Nanofiber Paper, Scattering, Efficient, Fibers, Film
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-187074 (URN)10.1021/acs.biomac.6b00145 (DOI)000374076900013 ()26942562 (PubMedID)2-s2.0-84964600674 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-17 Last updated: 2018-02-21Bibliographically approved
2. Lignin-Retaining Transparent Wood
Open this publication in new window or tab >>Lignin-Retaining Transparent Wood
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2017 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 17, p. 3445-3451Article in journal (Refereed) Published
Abstract [en]

Optically transparent wood, combining optical and mechanical performance, is an emerging new material for light-transmitting structures in buildings with the aim of reducing energy consumption. One of the main obstacles for transparent wood fabrication is delignification, where around 30wt% of wood tissue is removed to reduce light absorption and refractive index mismatch. This step is time consuming and not environmentally benign. Moreover, lignin removal weakens the wood structure, limiting the fabrication of large structures. A green and industrially feasible method has now been developed to prepare transparent wood. Up to 80wt% of lignin is preserved, leading to a stronger wood template compared to the delignified alternative. After polymer infiltration, a high-lignin-content transparent wood with transmittance of 83%, haze of 75%, thermal conductivity of 0.23WmK(-1), and work-tofracture of 1.2MJm(-3) (a magnitude higher than glass) was obtained. This transparent wood preparation method is efficient and applicable to various wood species. The transparent wood obtained shows potential for application in energy-saving buildings.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keyword
building materials, delignification, energy saving, lignin, wood
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-214873 (URN)10.1002/cssc.201701089 (DOI)000410136800018 ()2-s2.0-85029175474 (Scopus ID)
Note

QC 20171024

Available from: 2017-10-24 Created: 2017-10-24 Last updated: 2018-02-26Bibliographically approved
3. Transparent plywood
Open this publication in new window or tab >>Transparent plywood
(English)Manuscript (preprint) (Other academic)
Keyword
transparent wood; nanotechnology; wood composite; photonics
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-223451 (URN)
Note

QC 20180531

Available from: 2018-02-21 Created: 2018-02-21 Last updated: 2018-05-31Bibliographically approved
4. Nanostructured Wood Hybrids for Fire-Retardancy Prepared by Clay Impregnation into the Cell Wall
Open this publication in new window or tab >>Nanostructured Wood Hybrids for Fire-Retardancy Prepared by Clay Impregnation into the Cell Wall
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2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 41, p. 36154-36163Article in journal (Refereed) Published
Abstract [en]

Eco-friendly materials need "green" fire-retardancy treatments, which offer opportunity for new wood nanotechnologies. Balsa wood (Ochroma pyramidale) was delignified to form a hierarchically structured and nanoporous scaffold mainly composed of cellulose nanofibrils. This nanocellulosic wood scaffold was impregnated with colloidal montmorillonite clay to form a nanostructured wood hybrid with high flame-retardancy. The nanoporous scaffold was characterized by scanning electron microscopy and gas adsorption. Flame-retardancy was evaluated by cone calorimetry, whereas thermal and thermo-oxidative stabilities were assessed by thermogravimetry. The location of well-distributed clay nanoplatelets inside the cell walls was confirmed by energy-dispersive X-ray analysis. This unique nanostructure dramatically increased the thermal stability because of thermal insulation, oxygen depletion, and catalytic charring effects. A coherent organic/inorganic charred residue was formed during combustion, leading to a strongly reduced heat release rate peak and reduced smoke generation.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keyword
biocomposite, nanocomposite, layered silicate, nanocellulose, nanostructured, inorganic hybrid, wood nanotechnology
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-217436 (URN)10.1021/acsami.7b10008 (DOI)000413503700067 ()28825295 (PubMedID)2-s2.0-85031677298 (Scopus ID)
Note

QC 20171117

Available from: 2017-11-17 Created: 2017-11-17 Last updated: 2018-02-21Bibliographically approved
5. Wood Nanotechnology for Strong, Mesoporous, and Hydrophobic Biocomposites for Selective Separation of Oil/Water Mixtures
Open this publication in new window or tab >>Wood Nanotechnology for Strong, Mesoporous, and Hydrophobic Biocomposites for Selective Separation of Oil/Water Mixtures
2018 (English)In: ACS Nano, ISSN 1936-0851Article in journal (Other (popular science, discussion, etc.)) Published
Abstract [en]

Tremendous efforts have been dedicated to developing effective and eco-friendly approaches for separation of oil–water mixtures. Challenges remain in terms of complex processing, high material cost, low efficiency, and scale-up problems. Inspired by the tubular porosity and hierarchical organization of wood, a strong, mesoporous, and hydrophobic three-dimensional wood structure is created for selective oil/water separation. A delignified wood template with hydrophilic characteristics is obtained by removal of lignin. The delignified wood template is further functionalized by a reactive epoxy–amine system. This wood/epoxy biocomposite reveals hydrophobic/oleophilic functionality and shows oil absorption as high as 15 g/g. The wood/epoxy biocomposite has a compression yield strength and modulus up to 18 and 263 MPa, respectively, at a solid volume fraction of only 12%. This is more than 20 times that of cellulose-based foams/aerogels reconstructed from cellulose nanofibrils. The favorable performance is ascribed to the natural hierarchical honeycomb structure of wood. Oil can be selectively absorbed not only from below but also from above the water surface. High oil/water absorption capacity of both types of wood structures (delignified template and polymer-modified biocomposite) allows for applications in oil/water separation.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keyword
composite; delignification; hierarchical; mechanical; wetting; wood modification
National Category
Engineering and Technology
Research subject
Materials Science and Engineering; Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-223437 (URN)10.1021/acsnano.8b00005 (DOI)2-s2.0-85044513449 (Scopus ID)
Note

QC 20180221

Available from: 2018-02-21 Created: 2018-02-21 Last updated: 2018-02-21Bibliographically approved

Open Access in DiVA

The full text will be freely available from 2018-07-31 14:24
Available from 2018-07-31 14:24

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Fu, Qiliang

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