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  • 1.
    Berglund, Lars
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Polymerteknologi.
    Design of biodegradable cellulosic nanomaterials combining mechanical strength and optical transmittance2018Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Artikkel i tidsskrift (Annet vitenskapelig)
  • 2.
    Berglund, Lars
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal Inst Technol, WWSC, Fibre & Polymer Technol, Stockholm, Sweden..
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal Inst Technol, WWSC, Fibre & Polymer Technol, Stockholm, Sweden..
    Berthold, Fredrik
    RISE Bioecon, Stockholm, Sweden..
    Holocellulose fibers: combining mechanical performance and optical transmittance2019Inngår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Artikkel i tidsskrift (Annet vitenskapelig)
  • 3.
    Fu, Qiliang
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Yan, Min
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Jungstedt, Erik
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Li, Yuanyuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Transparent plywood as a load-bearing and luminescent biocomposite2018Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 164, s. 296-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transparent wood (TW) structures in research studies were either thin and highly anisotropic or thick and isotropic but weak. Here, transparent plywood (TPW) laminates are investigated as load-bearing biocomposites with tunable mechanical and optical performances. Structure-property relationships are analyzed. The plies of TPW were laminated with controlled fiber directions and predetermined stacking sequence in order to control the directional dependence of modulus and strength, which would give improved properties in the weakest direction. Also, the angular dependent light scattering intensities were investigated and showed more uniform distribution. Luminescent TPW was prepared by incorporation of quantum dots (QDs) for potential lighting applications. TPW can be designed for large-scale use where multiaxial load-bearing performance is combined with new optical functionalities.

    Fulltekst (pdf)
    fulltext
  • 4.
    Herrera, Martha
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Thitiwutthisakul, Kasinee
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Rujitanaroj, Pim-on
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Rojas, Ramiro
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer.
    Preparation and evaluation of high-lignin content cellulose nanofibrils from eucalyptus pulp2018Inngår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, nr 5, s. 3121-3133Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High Klason lignin content (23 wt%) cellulose nanofibrils (LCNF) were successfully isolated from eucalyptus pulp through catalyzed chemical oxidation, followed by high-pressure homogenization. LCNFs had a diameter of ca. 13 nm according to AFM evaluation. Dense films were obtained through vacuum filtration (nanopaper) and subjected to different drying methods. When drying under heat and mild vacuum (93 degrees C, 95 kPa) a higher water contact angle, lower roughness and oxygen transmission rate were observed, compared to those drying at room temperature under compression conditions. DSC experiments showed difference in signals associated to T-g of LCNF compared to CNF produced from spruce bleached pulp through enzymatic pre-treatment. The LCNF-based nanopaper showed mechanical properties slightly lower than for those made from cellulose nanofibrils, yet with increased hydrophobicity. In summary, the high-lignin content cellulose nanofibrils proved to be a suitable material for the production of low oxygen permeability nanopaper, with chemical composition close to native wood.

  • 5.
    Koskela, Salla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Wang, Shennan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Xu, Dingfeng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Li, Kai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    McKee, Lauren S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Bulone, Vincent
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Zhou, Qi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres2019Inngår i: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 21, nr 21, s. 5924-5933Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The production of cellulose nanofibres (CNFs) typically requires harsh chemistry and strong mechanical fibrillation, both of which have negative environmental impacts. A possible solution is offered by lytic polysaccharide monooxygenases (LPMOs), oxidative enzymes that boost cellulose fibrillation. Although the role of LPMOs in oxidative modification of cellulosic substrates is rather well established, their use in the production of cellulose nanomaterials is not fully explored, and the effect of the carbohydrate-binding module (CBM) on nanofibrillation has not yet been reported. Herein, we studied the activity of two LPMOs, one of which was appended to a CBM, on delignified softwood fibres for green and energy-efficient production of CNFs. The CNFs were used to prepare cellulose nanopapers, and the structure and properties of both nanofibres and nanopapers were determined. Both enzymes were able to facilitate nanocellulose fibrillation and increase colloidal stability of the produced CNFs. However, the CBM-lacking LPMO was more efficient in introducing carboxyl groups (0.53 mmol/g) on the cellulose fibre surfaces and releasing CNFs with thinner width (4.3 ± 1.5 nm) from delignified spruce fibres than the modular LPMO (carboxylate content of 0.38 mmol/g and nanofibre width of 6.7± 2.5 nm through LPMO pretreatment followed by mild homogenisation. The prepared nanopapers showed improved mechanical properties (tensile strength of 262 MPa, and modulus of 16.2 GPa) compared to conventional CNFs preparation methods, demonstrating the potential of LPMOs as green alternatives for cellulose nanomaterials preparation.

  • 6.
    Koskela, Salla
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Wang, Shennan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Li, Kai
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Srivastava, Vaibhav
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    McKee, Lauren S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Bulone, Vincent
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Zhou, Qi
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Glykovetenskap.
    Enzyme-assisted preparation of nanocellulose from wood holocellulose fibers2019Annet (Annet vitenskapelig)
  • 7.
    Li, Yuanyuan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Fu, Qiliang
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Yang, Xuan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Transparent wood for functional and structural applications2018Inngår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2112, artikkel-id 20170182Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Optically transparent wood combines mechanical performance with optical functionalities is an emerging candidate for applications in smart buildings and structural optics and photonics. The present review summarizes transparent wood preparation methods, optical and mechanical performance, and functionalization routes, and discusses potential applications. The various challenges are discussed for the purpose of improved performance, scaled-up production and realization of advanced applications. This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'.

    Fulltekst (pdf)
    fulltext
  • 8.
    Li, Yuanyuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Fu, Qiliang
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Rojas, Ramiro
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Yan, Max
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Fotonik.
    Berglund, Lars
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Towards centimeter thick transparent wood through interface manipulation2018Inngår i: International Journal of Materials and Chemistry, ISSN 2166-5346, E-ISSN 2166-5354, Vol. 6, s. 1094-1101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transparent wood is an attractive structural material for energy-saving buildings due to its high optical transmittance, good thermal insulation, and high toughness. However, thick highly transparent wood is challenging to realize. In the current work, highly transparent wood (1.5 mm) with a transmittance of 92%, close to that of pure PMMA (95%), is demonstrated. The high transmittance was realized by interface manipulation through acetylation of wood template. Both experiments and electromagnetic modeling support that the improved transmittance is mainly due to elimination of interface debonding gap. By applying this method, a centimeter-thick transparent wood structure was obtained. The transparent wood could be used as a substrate for an optically tunable window by laminating a polymer dispersed liquid crystal (PDLC) film on top. The techniques demonstrated are a step towards the replacement of glass in smart windows and smart buildings.

    Fulltekst (pdf)
    fulltext
  • 9.
    Mendoza-Galván, Arturo
    et al.
    Cinvestav-Querétaro, Libramiento Norponiente 2000, MX-76230 Querétaro, Mexico.
    Li, Yuanyuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Magnusson, Roger
    Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden.
    Järrendahl, Kenneth
    Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden.
    Berglund, Lars
    KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Arwin, Hans
    Department of Physics, Chemistry and Biology, Linköping University, SE-58183 Linköping, Sweden.
    Transmission mueller-matrix characterization of transparent ramie films2020Inngår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, Vol. 38, nr 1, artikkel-id 014008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ramie is a plant whose fibers are used in fabrics. Ramie films are prepared by hot pressing and studied with transmission Mueller-matrix ellipsometry, which provides a complete description of polarizing and depolarizing sample properties. Symmetries of the Mueller matrices imply that the ramie films are linearly birefringent and act as waveplates. The linear birefringence is quantified by the differential decomposition of the Mueller matrices and the materials’ birefringence is found to be of the order of 0.05–0.08 with small dispersion in the visible spectral range. The films exhibit depolarization, which is quantified in terms of the depolarization index and varies from 0.9 in the infrared to 0.25 in the ultraviolet range. The deep understanding of ramie films’ polarization properties will pave the way for applications in optical and photonic devices.

    Fulltekst (pdf)
    fulltext
  • 10.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal institute of technology.
    Eco-friendly Holocellulose Materials for Mechanical Performance and Optical Transmittance2019Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

    Fulltekst tilgjengelig fra 2020-11-19 09:42
  • 11.
    Yang, Xuan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Oriented all-cellulose film based on ramie fiber with high mechanical property and transparency2017Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Artikkel i tidsskrift (Annet vitenskapelig)
  • 12.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal institute of technology.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Recycling without Fiber Degradation: Strong Paper Structures for 3D Forming Based on Nanostructurally Tailored Wood Holocellulose FibersManuskript (preprint) (Annet vitenskapelig)
  • 13.
    Yang, Xuan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Water-Based Approach to High-Strength All-Cellulose Material with Optical Transparency2018Inngår i: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 6, nr 1, s. 501-510Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 14.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    High-Density Molded Cellulose Fibers and Transparent Biocomposites Based on Oriented Holocellulose2019Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, nr 10, s. 10310-10319Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 15.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    RISE Res Inst Sweden, Master Samuelsgatan 60, SE-11121 Stockholm, Sweden..
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency2018Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, nr 7, s. 3020-3029Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 16.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Reid, Michael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsén, Peter
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Eco-Friendly Cellulose Nanofibrils Designed by Nature: Effects from Preserving Native StateManuskript (preprint) (Annet vitenskapelig)
  • 17.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Reid, Michael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsén, Peter
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Eco-Friendly Cellulose Nanofibrils Designed by Nature: Effects from Preserving Native State2020Inngår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 14, nr 1, s. 724-735Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cellulose nanofibrils (CNFs) show high modulus and strength and are already used in industrial applications. Mechanical properties of neat CNF films or CNF-polymer matrix nanocomposites are usually much better than for polymer matrix composite films reinforced by clay, graphene, graphene oxide, or carbon nanotubes. In order to obtain small CNF diameter and colloidal stability, chemical modification has so far been necessary, but this increases cost and reduces eco-friendly attributes. In this study, an unmodified holocellulose CNF (Holo-CNF) with small diameter is obtained from mildly peracetic acid delignified wood fibers. CNF is readily defibrillated by low-energy kitchen blender processing. The hemicellulose coating on individual fibrils in the wood plant cell wall is largely preserved in Holo-CNF. This "native" CNF shows well-preserved native fibril structure in terms of length (similar to 2.1 mu m), diameter (<5 nm), high crystallinity, high cellulose molar mass, electronegative charge, and limited mechanical processing damage. The hemicellulose coating contributes mechanical properties and high optical transmittance for CNF nanopaper, which can otherwise only be achieved with chemically modified CNFs. The CNF nanopaper shows superior mechanical properties with a Young's modulus of 21 GPa and an ultimate strength of 320 MPa. Moreover, hemicellulose imparts recyclability from the dried state. Altogether, this native CNF represents a class of colloidally stable, eco-friendly, low-cost CNF of small diameter for large-scale applications of nanopaper and nanomaterials.

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