| 1. |
- Achtel, Christian, et al.
(författare)
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Dissolution capacity of novel cellulose solvents based on triethyloctylammonium chloride
- 2017
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 218:21
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Tidskriftsartikel (refereegranskat)abstract
- Dissolution of cellulose from various sources (microcrystalline cellulose and different dissolving grade pulp fibers) is investigated in solvent systems based on triethyl(n-octyl)ammonium chloride (N2228Cl). Clear cellulose solutions are obtained with N2228Cl in a variety of solvents, e.g., dimethyl sulfoxide, N,N-dimethylacetamide, and acetone. It is possible to prepare clear cellulose solutions from pulp fibers with concentrations up to 15 wt%. However, it is found that the cellulose is degraded, especially when neat (i.e., molten) N2228Cl is used as a solvent. The present work includes comprehensive rheological characterization of the cellulose solutions, both with shear and extensional rheology. In most cases, the viscosity values are low (complex viscosities below 100 Pa s for 5–10 wt% dissolved cellulose), and the solutions show more Newtonian than viscoelastic behavior.
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| 2. |
- Achtel, Christian, et al.
(författare)
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Surprising Insensitivity of Homogeneous Acetylation of Cellulose Dissolved in Triethyl(n-octyl)ammonium Chloride/Molecular Solvent on the Solvent Polarity
- 2018
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Ingår i: Macromolecular materials and engineering. - : Wiley-VCH Verlag. - 1438-7492 .- 1439-2054. ; 303:5
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Tidskriftsartikel (refereegranskat)abstract
- The homogeneous acetylation of microcrystalline cellulose (MCC) by acetyl chloride and acetic anhydride in triethyl(n-octyl)ammonium chloride (N2228Cl)/molecular solvents (MSs) is investigated. The reaction with both acylating agents shows the expected increase of the degree of substitution (DS) on reaction temperature and time. Under comparable reaction conditions, however, DS is surprisingly little dependent on the MS employed, although the MSs differ in empirical polarity by 7 kcal mol−1 as calculated by use of solvatochromic probes. The empirical polarities of (MCC + N2228Cl + MS) differ only by 0.8 kcal mol−1. The formation a polar electrolyte sheath around cellulose chains presumably contributes to this “leveling-off†of the dependence DS on the polarity of the parent MS employed. N2228Cl recovery and recycling is feasible. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 3. |
- Argyropoulos, Dimitris D. S., et al.
(författare)
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Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges
- 2023
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Ingår i: ChemSusChem. - : John Wiley and Sons Inc. - 1864-5631 .- 1864-564X. ; 16:23
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Forskningsöversikt (refereegranskat)abstract
- Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.
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| 4. |
- Bengtsson, Andreas, et al.
(författare)
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Continuous Stabilization and Carbonization of a Lignin–Cellulose Precursor to Carbon Fiber
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:19, s. 16793-16802
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Tidskriftsartikel (refereegranskat)abstract
- : The demand for carbon fibers (CFs) based onrenewable raw materials as the reinforcing fiber in composites forlightweight applications is growing. Lignin−cellulose precursorfibers (PFs) are a promising alternative, but so far, there is limitedknowledge of how to continuously convert these PFs underindustrial-like conditions into CFs. Continuous conversion is vitalfor the industrial production of CFs. In this work, we havecompared the continuous conversion of lignin−cellulose PFs (50wt % softwood kraft lignin and 50 wt % dissolving-grade kraft pulp)with batchwise conversion. The PFs were successfully stabilizedand carbonized continuously over a total time of 1.0−1.5 h,comparable to the industrial production of CFs from polyacrylonitrile. CFs derived continuously at 1000 °C with a relative stretch of−10% (fiber contraction) had a conversion yield of 29 wt %, a diameter of 12−15 μm, a Young’s modulus of 46−51 GPa, and atensile strength of 710−920 MPa. In comparison, CFs obtained at 1000 °C via batchwise conversion (12−15 μm diameter) with arelative stretch of 0% and a conversion time of 7 h (due to the low heating and cooling rates) had a higher conversion yield of 34 wt%, a higher Young’s modulus (63−67 GPa) but a similar tensile strength (800−920 MPa). This suggests that the Young’s moduluscan be improved by the optimization of the fiber tension, residence time, and temperature profile during continuous conversion,while a higher tensile strength can be achieved by reducing the fiber diameter as it minimizes the risk of critical defects.
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| 5. |
- Bengtsson, Andreas, et al.
(författare)
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Improved yield of carbon fibres from cellulose and kraft lignin
- 2018
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:12, s. 1007-1016
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Tidskriftsartikel (refereegranskat)abstract
- To meet the demand for carbon-fibre-reinforced composites in lightweight applications, cost-efficient processing and new raw materials are sought for. Cellulose and kraft lignin are each interesting renewables for this purpose due to their high availability. The molecular order of cellulose is an excellent property, as is the high carbon content of lignin. By co-processing cellulose and lignin, the advantages of these macromolecules are synergistic for producing carbon fibre (CF) of commercial grade in high yields. CFs were prepared from precursor fibres (PFs) made from 70:30 blends of softwood kraft lignin (SW-KL) and cellulose by dry-jet wet spinning with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) as a solvent. In focus was the impact of the molecular mass of lignin and the type of cellulose source on the CF yield and properties, while membrane-filtrated kraft lignin and cellulose from dissolving kraft pulp and fully bleached paper-grade SW-KP (kraft pulp) served as sources. Under the investigated conditions, the yield increased from around 22% for CF from neat cellulose to about 40% in the presence of lignin, irrespective of the type of SW-KL. The yield increment was also higher relative to the theoretical one for CF made from blends (69%) compared to those made from neat celluloses (48-51%). No difference in the mechanical properties of the produced CF was observed.
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| 6. |
- Bengtsson, Jenny, et al.
(författare)
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Chemical Recycling of a Textile Blend from Polyester and Viscose, Part II : Mechanism and Reactivity during Alkaline Hydrolysis of Textile Polyester
- 2022
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Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- Chemical recycling of textiles holds the potential to yield materials of equal quality and value as products from virgin feedstock. Selective depolymerization of textile polyester (PET) from regenerated cellulose/PET blends, by means of alkaline hydrolysis, renders the monomers of PET while cellulose remains in fiber form. Here, we present the mechanism and reactivity of textile PET during alkaline hydrolysis. Part I of this article series focuses on the cellulose part and a possible industrialization of such a process. The kinetics and reaction mechanism for alkaline hydrolysis of polyester packaging materials or virgin bulk polyester are well described in the scientific literature; however, information on depolymerization of PET from textiles is sparse. We find that the reaction rate of hydrolysis is not affected by disintegrating the fabric to increase its surface area. We ascribe this to the yarn structure, where texturing and a low density assures a high accessibility even without disintegration. The reaction, similar to bulk polyester, is shown to be surface specific and proceeds via endwise peeling. Finally, we show that the reaction product terephthalic acid is pure and obtained in high yields. © 2022 by the authors.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Bengtsson, Jenny, et al.
(författare)
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Identifying breach mechanism during air-gap spinning of lignin–cellulose ionic-liquid solutions
- 2019
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Ingår i: Journal of Applied Polymer Science. - : John Wiley and Sons Inc.. - 0021-8995 .- 1097-4628.
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Tidskriftsartikel (refereegranskat)abstract
- To be able to produce highly oriented and strong fibers from polymer solutions, a high elongational rate during the fiber-forming process is necessary. In the air-gap spinning process, a high elongational rate is realized by employing a high draw ratio, the ratio between take-up and extrusion velocity. Air-gap spinning of lignin–cellulose ionic-liquid solutions renders fibers that are promising to use as carbon fiber precursors. To further improve their mechanical properties, the polymer orientation should be maximized. However, achieving high draw ratios is limited by spinning instabilities that occur at high elongational rates. The aim of this experimental study is to understand the link between solution properties and the critical draw ratio during air-gap spinning. A maximum critical draw ratio with respect to temperature is found. Two mechanisms that limit the critical draw ratio are proposed, cohesive breach and draw resonance, the latter identified from high-speed videos. The two mechanisms clearly correlate with different temperature regions. The results from this work are not only of value for future work within the studied system but also for the design of air-gap spinning processes in general.
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| 11. |
- Bengtsson, Jenny, 1990, et al.
(författare)
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Mass transport and yield during spinning of lignin-cellulose carbon fiber precursors
- 2019
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 1437-434X .- 0018-3830. ; 73:5, s. 509-516
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, a substance considered as a residue in biomass and ethanol production, has been identified as a renewable resource suitable for making inexpensive carbon fibers (CFs), which would widen the range of possible applications for light-weight CFs reinforced composites. Wet spinning of lignin-cellulose ionic liquid solutions is a promising method for producing lignin-based CFs precursors. However, wet-spinning solutions containing lignin pose technical challenges that have to be solved to enable industrialization. One of these issues is that a part of the lignin leaches into the coagulation liquid, which reduces yield and might complicate solvent recovery. In this work, the mass transport during coagulation is studied in depth using a model system and trends are confirmed with spinning trials. It was discovered that during coagulation, efflux of ionic liquid is not hindered by lignin concentration in solution and the formed cellulose network will enclose soluble lignin. Consequently, a high total concentration of lignin and cellulose in solution is advantageous to maximize yield. This work provides a fundamental understanding on mass transport during coagulation of lignin-cellulose solutions, crucial information when designing new solution-based fiber forming processes.
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| 12. |
- Bengtsson, Jenny, et al.
(författare)
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Preventing fiber-fiber adhesion of lignin-cellulose precursors and carbon fibers with spin finish application
- 2023
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Ingår i: Holzforschung. - : De Gruyter Open Ltd. - 0018-3830 .- 1437-434X. ; 77, s. 648-
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Tidskriftsartikel (refereegranskat)abstract
- Adhesion of fibers within a spun tow, including carbon fibers and precursors, is undesirable as it may interrupt the manufacturing process and entail inferior fiber properties. In this work, softwood kraft lignin was used together with a dissolving pulp to spin carbon fiber precursors. Lignin-cellulose precursors have previously been found to be prone to fiber fusion, both post-spinning and during carbon fiber conversion. In this study, the efficiency of applying different kinds of spin finishes, with respect to rendering separable precursors and carbon fibers, has been investigated. It was found that applying a cationic surfactant, and to a similar extent a nonionic surfactant, resulted in well separated lignin-cellulose precursor tows. Furthermore, the fiber separability after carbon fiber conversion was evaluated, and notably, precursors treated with a silicone-based spin finish generated the most well-separated carbon fibers. The underlying mechanism of fiber fusion post-spinning and converted carbon fibers is discussed.
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| 13. |
- Bengtsson, Jenny, et al.
(författare)
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The challenge of predicting spinnability : Investigating benefits of adding lignin to cellulose solutions in air-gap spinning
- 2021
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Ingår i: Journal of Applied Polymer Science. - : John Wiley and Sons Inc. - 0021-8995 .- 1097-4628. ; 138:26
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the underlying mechanism for improved spinnability when mixing lignin and cellulose in solution was investigated. Co-processing of lignin and cellulose has previously been identified as a potential route for production of inexpensive and bio-based carbon fibers. The molecular order of cellulose contributes to the strength of the fibers and the high carbon content of lignin improves the yield during conversion to carbon fibers. The current work presents an additional benefit of combining lignin and cellulose; solutions that contain both lignin and cellulose could be air-gap spun at substantially higher draw ratios than pure cellulose solutions, that is, lignin improved the spinnability. Fibers were spun from solutions containing different ratios of lignin, from 0 to 70 wt%, and the critical draw ratio was determined at various temperatures of solution. The observations were followed by characterization of the solutions with shear and elongational viscosity and surface tension, but none of these methods could explain the beneficial effect of lignin on the spinnability. However, by measuring the take-up force it was found that lignin seems to stabilize against diameter fluctuations during spinning, and plausible explanations are discussed
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| 14. |
- El Seoud, Omar A, et al.
(författare)
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Cellulose in Ionic Liquids and Alkaline Solutions : Advances in the Mechanisms of Biopolymer Dissolution and Regeneration.
- 2019
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- This review is focused on assessment of solvents for cellulose dissolution and the mechanism of regeneration of the dissolved biopolymer. The solvents of interest are imidazole-based ionic liquids, quaternary ammonium electrolytes, salts of super-bases, and their binary mixtures with molecular solvents. We briefly discuss the mechanism of cellulose dissolution and address the strategies for assessing solvent efficiency, as inferred from its physico-chemical properties. In addition to the favorable effect of lower cellulose solution rheology, microscopic solvent/solution properties, including empirical polarity, Lewis acidity, Lewis basicity, and dipolarity/polarizability are determinants of cellulose dissolution. We discuss how these microscopic properties are calculated from the UV-Vis spectra of solvatochromic probes, and their use to explain the observed solvent efficiency order. We dwell briefly on use of other techniques, in particular NMR and theoretical calculations for the same purpose. Once dissolved, cellulose is either regenerated in different physical shapes, or derivatized under homogeneous conditions. We discuss the mechanism of, and the steps involved in cellulose regeneration, via formation of mini-sheets, association into "mini-crystals", and convergence into larger crystalline and amorphous regions. We discuss the use of different techniques, including FTIR, X-ray diffraction, and theoretical calculations to probe the forces involved in cellulose regeneration.
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| 15. |
- El Seoud, Omar, et al.
(författare)
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Cellulose, chitin and silk : the cornerstones of green composites
- 2022
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Ingår i: Emergent Materials. - : Springer Nature. - 2522-5731 .- 2522-574X. ; 5:3, s. 785-
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Tidskriftsartikel (refereegranskat)abstract
- This overview article is concerned with fabrication and applications of the composites of three major biopolymers, cellulose (Cel), chitin (Chn)/chitosan (Chs), and silk fibroin (SF). A brief discussion of their molecular structures shows that they carry functional groups (-OH, -NH-COCH3, -NH2, -CONH-) whose hydrogen-bonding, and der Waals interactions lead to semi-crystalline structures in the solid phase. There are several classes of solvents that disrupt these interactions, hence dissolve the above-mentioned biopolymers. These include solutions of inorganic and organic electrolytes in dipolar aprotic solvents (DASs), ionic liquids (ILs), and their solutions in DASs. Mixing of biopolymer solutions leads to efficient mutual interactions, hence formation of relatively homogeneous composites. These are then regenerated in non-solvents (water, ethanol, acetone) in different physical forms, e.g., fibers, nanoparticles and films. We discuss the fabrication of these products that have enormous potential use in the textile industry, in medicine, in the food industry, and decontamination of fluids. These applications will most certainly expand due to the attractive characteristics of these composites (renewability, sustainability, biodegradation) and the increased public concern about the adverse environmental impact of petroleum-based polymers, as recently shown by the presence of microplastics in air, water, land, and food (Akdogan & Guven in Environ Pollut. 254:113011 (2019)).
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| 16. |
- El Seoud, Omar, et al.
(författare)
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Cellulose Regeneration and Chemical Recycling : Closing the “Cellulose Gap” Using Environmentally Benign Solvents
- 2020
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Ingår i: Macromolecular materials and engineering. - : Wiley-VCH Verlag. - 1438-7492 .- 1439-2054. ; 305:4
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Tidskriftsartikel (refereegranskat)abstract
- Strategies to mitigate the expected “cellulose gap” include increased use of wood cellulose, fabric reuse, and recycling. Ionic liquids (ILs) are employed for cellulose physical dissolution and shaping in different forms. This review focuses on the regeneration of dissolved cellulose as nanoparticles, membranes, nonwoven materials, and fibers. The solvents employed in these applications include ILs and alkali solutions without and with additives. Cellulose fibers obtained via the carbonate and carbamate processes are included. Chemical recycling (CR) of polycotton (cellulose plus poly(ethylene terephthalate)) is addressed because depending on the recycling approach employed, this process is akin to regeneration. The strategies investigated in CR include preferential dissolution or depolymerization of one component of the blend, and separation of both components using ILs. It is hoped that this review focuses the attention on the potential applications of regenerated cellulose from its solutions and contributes to the important environmental issue of recycling of used materials.
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| 17. |
- Jedvert, Kerstin, et al.
(författare)
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Adsorption Studies of Amino Cellulose on Cellulosics
- 2017
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Ingår i: Macromolecular materials and engineering. - : Wiley. - 1438-7492 .- 1439-2054. ; 302:7
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of a typical example of a new class of amino cellulose, namely 6-deoxy-6-(2-aminoethyl)amino cellulose at different pH-values and in the presence of electrolytes, onto cellulose model substrates is studied with surface plasmon resonance and quartz crystal microbalance with dissipation monitoring. Unexpectedly, adsorption is consistently higher at a higher pH-value of 10, indicating that solubility and interactions between amine moieties and cellulose are more important than electrostatic interactions. The findings are highly relevant for the process to modify material surfaces with amino cellulose in water-based systems as a universal tool for changing the surface properties and chemistry. Potential applications for an antimicrobial all biobased material could be found, e.g., as medical textiles or in the biotechnology sector.
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| 18. |
- Jedvert, Kerstin, et al.
(författare)
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Analyses of wood components in mild steam explosion liquors from spruce
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 29:4, s. 557-566
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Tidskriftsartikel (refereegranskat)abstract
- Steam explosion at mild conditions is an intriguing pre-treatment method for future biorefineries. Here, mild steam explosion liquors, i.e. the condensed steam generated from water-impregnated and NaBH4-impregnated spruce at various steam explosion conditions, are comprehensively characterized. The characterization includes several chromatographic techniques along with nuclear magnetic resonance (NMR), in order to determine relative abundances of solubilized lignin, carbohydrates, and acetate content. The findings show that the main components in the liquors originated from hemicelluloses and, to some extent, wood extractives. Arabinose side substituents of arabinoglucuronoxylan were cleaved early during the steam treatment. The amount of (galacto) glucomannan in the liquors increased from 16% for the sample from the 4 bar (0.4 MPa) treatment, to 23% for the sample from the 7 bar treatment. The effects of different conditions on wood during NaBH4-treatment were also investigated. For this treatment, it was found that the degree of deacetylation increased at harsher conditions.
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| 19. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Analyses of wood components in mild steam explosion liquors from spruce
- 2014
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 29:4, s. 557-566
-
Tidskriftsartikel (refereegranskat)abstract
- Steam explosion at mild conditions is an intriguing pre-treatment method for future biorefineries. Here, mild steam explosion liquors, i.e. the condensed steam generated from water-impregnated and NaBH4-impregnated spruce at various steam explosion conditions, are comprehensively characterized. The characterization includes several chromatographic techniques along with nuclear magnetic resonance (NMR), in order to determine relative abundances of solubilized lignin, carbohydrates, and acetate content. The findings show that the main components in the liquors originated from hemicelluloses and, to some extent, wood extractives. Arabinose side substituents of arabinoglucuronoxylan were cleaved early during the steam treatment. The amount of (galacto) glucomannan in the liquors increased from 16% for the sample from the 4 bar (0.4 MPa) treatment, to 23% for the sample from the 7 bar treatment. The effects of different conditions on wood during NaBH4-treatment were also investigated. For this treatment, it was found that the degree of deacetylation increased at harsher conditions.
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| 20. |
- Jedvert, Kerstin, et al.
(författare)
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Cellulose modification and shaping – a review
- 2017
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Ingår i: Journal of polymer engineering. - : Walter de Gruyter GmbH. - 0334-6447 .- 2191-0340. ; 37:9, s. 845-860
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Tidskriftsartikel (refereegranskat)abstract
- This review aims to present cellulose as a versatile resource for the production of a variety of materials, other than pulp and paper. These products include fibers, nonwovens, films, composites, and novel derivatized materials. This article will briefly introduce the structure of cellulose and some common cellulose derivatives, as well as the formation of cellulosic materials in the micro- and nanoscale range. The challenge with dissolution of cellulose will be discussed and both derivatizing and nonderivatizing solvents for cellulose will be described. The focus of the article is the critical discussion of different shaping processes to obtain a variety of cellulose products, from commercially available viscose fibers to advanced and functionalized materials still at the research level.
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| 21. |
- Jedvert, Kerstin, et al.
(författare)
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Cellulosic nonwovens produced via efficient solution blowing technique
- 2020
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Ingår i: Journal of Applied Polymer Science. - : John Wiley and Sons Inc.. - 0021-8995 .- 1097-4628. ; 137:5
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Tidskriftsartikel (refereegranskat)abstract
- The demand for nonwoven materials has increased during the last few years and is expected to increase further due to its use in a broad range of new application areas. Today, the majority of nonwovens are from petroleum-based resources but there is a desideratum to develop sustainable and competitive materials from renewable feedstock. In this work, renewable nonwovens are produced by solution blowing of dissolved cellulose using 1-ethyl-3-methylimidazolium acetate (EMIMAc) as solvent. Properties of cellulose solutions and process parameters, such as temperature, flow rate, air pressure, and distance to collector, are evaluated in respect to spinnability and material structural properties. Nonwovens with fiber diameters mainly in the micrometer range were successfully produced and it was shown that high temperature or low flow rate resulted in thinner fibers. The produced materials were stiffer (higher effective stress and lower strain) compared to commercial polypropylene nonwoven. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48339. © 2019 The Authors.
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| 22. |
- Jedvert, Kerstin, et al.
(författare)
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Extraction of hemicelluloses after chemical pretreatment combined with mild steam explosion
- 2011
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Ingår i: 16th International Symposium on Wood, Fiber and Pulping Chemistry - Proceedings. - : CHINA LIGHT INDUSTRY PRESS. ; , s. 867-871
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Konferensbidrag (refereegranskat)abstract
- The aim of this research is to separate different wood components from softwood as a first step towards development of novel materials made from Scandinavian wood. The approach is pre-treatment with a reducing agent in combination with mild steam explosion (T< 160°C, t < 15 min); followed by extraction with different liquors. The aim is to retain an increased amount of hemicelluloses in general, and glucomannans in particular, during chemical treatments, preferably of high molecular weight. Experiments were performed on wood chips from spruce in small scale steam explosion equipment. A pre-treatment method with sodium borohydride (NaBH 4) as a reducing agent model substance was chosen. Wood chips pre-treated with NaBH 4 were compared to untreated chips, and the chips were treated with steam explosion followed by extraction in alkali. Results showed that a higher amount of glucomannan was retained in chips treated with NaBH 4 than in untreated chips. An increase in the extraction rate as an effect of steam explosion indicates a possible combination of chemical reactions that breaks up the lignin-polysaccharide network and a more porous wood structure. An experimental series with wood powder as raw material were also performed in order to study the chemical reactions during steam explosion, e. g. autohydrolysis. Water impregnated wood powder as well as wood powder treated with NaBH 4 was subjected to mild steam explosion for different retention times. It was shown that a decrease in hemicelluloses content occurred after only 5 min, and the degradation was more severe at longer residence times. However, the degradation of hemicelluloses was not as severe as in the chemical treatments at conditions corresponding to chemical pulping, and consequently might be a more prudent method to access the wood structure. Extractions after steam explosion were investigated at different pH levels, and the results showed that most of the glucomannan was still in the wood residue at the tested conditions. The stabilization of glucomannans by pre-treatment with NaBH 4 was clearly seen also in these experiments.
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| 23. |
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| 24. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Mild steam explosion: A way to activate wood for enzymatic treatment, chemical pulping and biorefinery processes
- 2012
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Ingår i: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 27:5, s. 828-835
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Tidskriftsartikel (refereegranskat)abstract
- Industrially chipped wood chips of Norway spruce (Picea abies) were subjected to mild steam explosion (115 - 160 degrees C) in a small-scale steam explosion reactor. This was followed by kraft cooking or extraction in alkali at 130 degrees C for two hours, or by an enzymatic treatment with a culture filtrate in order to investigate the efficiency of the process in opening wood structure. The results demonstrated that mild explosion has an effect on opening wood structure, shown by increased release of glucomannans during alkaline extraction and faster delignification in kraft cooks for steam-exploded samples. The effect was also shown by analysis of the released reducing sugars of enzymatic treated wood chips, which showed that the wood structure became accessible for enzymes even at very modest mild steam explosion conditions. This was not observed in untreated wood chips, used as reference. The enzyme activity increased with increased temperature during mild steam explosion, and the effect did not seem to be linear. The mechanical effect of steam explosion seems to be of great importance at lower temperatures, and both chemical and mechanical effects are important at higher steam explosion temperatures. Samples for enzymatic treatment were taken both from the edges of wood chips as well as from the middle part of the chips, and the effect of steam explosion was somewhat greater in samples from the middle parts.
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| 25. |
- Jedvert, Kerstin, 1984, et al.
(författare)
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Mild Steam Explosion and Chemical Pre-Treatment of Norway Spruce
- 2012
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 7:2, s. 2051-2074
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to open up the structure of wood while retaining a large amount of hemicelluloses, in particular (galacto)glucomannans. The effects of pre-treatments on wood meal from spruce (Picea abies) with a reducing agent (NaBH4) combined with steam explosion at very mild conditions were investigated. The effects of steam explosion at 160 degrees C were studied for various residence times (5 to 35 min) on both water-impregnated wood meal and samples pre-treated with NaBH4. The findings showed that pre-treatment with sodium borohydride stabilized the reducing end-groups of glucomannans and that the treatment was effective both during mild steam explosion, for both long and short residence times, as well as during subsequent treatment in alkali. Extraction experiments at different pH and temperatures showed that the main part of the hemicelluloses still remained in the wood residue after treatment. The molecular weight distributions of the extracted material from the liquors indicated that there were broad molecular distributions and that the molecular weight averages were between 3 and 6 kDa.
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