| 1. |
- Bengtsson, Andreas, et al.
(författare)
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Carbon Fibers from Lignin-Cellulose Precursors : Effect of Stabilization Conditions
- 2019
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society. - 2168-0485. ; 7:9, s. 8440-8448
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing demand for lightweight composites reinforced with carbon fibers (CFs). Due to its high availability and carbon content, kraft lignin has gained attention as a potential low-cost CF precursor. CFs with promising properties can be made from flexible dry-jet wet spun precursor fibers (PFs) from blends (70:30) of softwood kraft lignin and fully bleached softwood kraft pulp. This study focused on reducing the stabilization time, which is critical in CF manufacturing. The impact of stabilization conditions on chemical structure, yield, and mechanical properties was investigated. It was possible to reduce the oxidative stabilization time of the PFs from about 16 h to less than 2 h, or even omitting the stabilization step, without fusion of fibers. The main reactions involved in the stabilization stage were dehydration and oxidation. The results suggest that the isothermal stabilization at 250 °C override the importance of having a slow heating rate. For CFs with a commercial diameter, stabilization of less than 2 h rendered in tensile modulus 76 GPa and tensile strength 1070 MPa. Impregnation with ammonium dihydrogen phosphate significantly increased the CF yield, from 31-38 to 46-50 wt %, but at the expense of the mechanical properties.
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| 2. |
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- Myrendal, Jenny, 1975, et al.
(författare)
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Children’s bodily and sexual integrity: Word meaning negotiation in online forum discussions
- 2019
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Ingår i: Lavender Languages and Linguistics 26, Gothenburg 2-4 May.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The discourses surrounding young children’s bodily and sexual integrity are diverse and at times contradictory. Positions on children’s right to knowledge about self-determination over their own bodies sometimes conflict with positions advocating that such information should not be forced upon children who are too young (and too innocent) to understand “adult issues”. Teaching materials dealing with the topic also switch between perspectives; on the one hand taking the perspective of the adult role-model instilling sound values in children about where bodily boundaries should be drawn, on the other hand encouraging the children themselves to follow their intuition about what “feels right”. In this paper, we investigate how participants in discussions in an online Swedish discussion forum negotiate their respective takes on the meaning of the notion ‘children’s integrity’ by engaging in processes of word meaning negotiation (Myrendal 2015, 2019). We empirically explore how arguments are formed and what positions are taken in the negotiation process amongst the parties involved in the online discussions, and analyse how the interlocutors jointly form a common understanding. We also compare how the notion of children’s integrity is made sense of within the online interactions with how it has been framed within policy documents such as the national curriculum for preschools, and recent materials on children, integrity and rights.
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| 7. |
- Van Odijk, Jenny, 1969, et al.
(författare)
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Measurements of eosinophil activation before and after food challenges in adults with food hypersensitivity
- 2006
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Ingår i: Int Arch Allergy Immunol. - : S. Karger AG. - 1018-2438 .- 1423-0097. ; 140:4, s. 334-41
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Objective assessment of inflammatory reactions in the gastrointestinal tract could be useful in the diagnosis of food hypersensitivity. The aim of the present study was to investigate the involvement of eosinophils and mast cells in the inflammatory response of patients with food hypersensitivity before and after food challenges. METHODS: Eleven patients (4 with IgE-mediated allergy and 7 without) with food hypersensitivity and positive double-blind, placebo-controlled food challenge were subjected to food challenge in a single-blinded fashion. Four subjects with no known food hypersensitivity were recruited as controls. Placebo was given after a 1-week washout period followed by an active dose. Stool, urinary and serum samples were collected and symptoms were recorded in a diary. Fecal samples were analyzed for eosinophil protein X (F-EPX) and tryptase; urinary samples for EPX (U-EPX) and leukotriene E4 (U-LTE4) and serum samples were analyzed for eotaxin and food-specific IgE antibodies. RESULTS: Patients with IgE-mediated food allergy had increased levels of F-EPX compared to controls and tended to have lower serum levels of eotaxin compared to non-allergic patients and controls. U-LTE4 was significantly higher in allergic patients compared to non-allergic patients after challenge. Moreover, F-EPX correlated to U-LTE4 (p = 0.011). Reported symptoms, abdominal pain, distension, flatulence and nausea were similar in the allergic and non-allergic patients. CONCLUSION: The results strongly indicate that eosinophils are activated in the gastrointestinal tract of food-allergic patients but not in patients with non-allergic food hypersensitivity. Due to the inconsistent pattern of symptoms after placebo and active food challenge, it was not possible to relate the levels of inflammation markers to the recorded symptoms.
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| 8. |
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| 9. |
- Andersson Trojer, Markus, 1981, et al.
(författare)
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Directed self-assembly of silica nanoparticles in ionic liquid-spun cellulose fibers
- 2019
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 553, s. 167-176
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Tidskriftsartikel (refereegranskat)abstract
- The application range of man-made cellulosic fibers is limited by the absence of cost- and manufacturing-efficient strategies for anisotropic hierarchical functionalization. Overcoming these bottlenecks is therefore pivotal in the pursuit of a future bio-based economy. Here, we demonstrate that colloidal silica nanoparticles (NPs), which are cheap, biocompatible and easy to chemically modify, enable the control of the cross-sectional morphology and surface topography of ionic liquid-spun cellulose fibers. These properties are tailored by the silica NPs’ surface chemistry and their entry point during the wet-spinning process (dope solution DSiO2 or coagulation bath CSiO2). For CSiO2-modified fibers, the coagulation mitigator dimethylsulphoxide allows for controlling the surface topography and the amalgamation of the silica NPs into the fiber matrix. For dope-modified fibers, we hypothesize that cellulose chains act as seeds for directed silica NP self-assembly. This results for DSiO2 in discrete micron-sized rods, homogeneously distributed throughout the fiber and for glycidoxy-surface modified DSiO2@GLYEO in nano-sized surface aggregates and a cross-sectional core-shell fiber morphology. Furthermore, the dope-modified fibers display outstanding strength and toughness, which are both characteristic features of biological biocomposites.
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| 10. |
- Bachinger, Angelika, et al.
(författare)
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The morphology of ABS with phosphorus-based flame-retardants and its influence on the impact performance
- 2021
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Ingår i: Abstract Book of FRPM21. ; , s. 86-87
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Konferensbidrag (refereegranskat)abstract
- Halogen-free flame-retardants (HFFRs) have a pronounced effect on the impact performance of ABS. The addition of flame-retardant (FR) particles may interfere with the morphology of ABS or introduce weak spots into the plastic. The present work studies the morphology of ABS with phosphorus-based flame-retardant systems and sets it in relation to their respective impact performance with the aim of identifying mechanisms influencing the impact performance and revealing possibilities to overcome this issue.
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