| 1. |
- Plackett, David, et al.
(författare)
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Physical Properties and Morphology of Films Prepared from Microfibrillated Cellulose and Microfibrillated Cellulose in Combination with Amylopectin
- 2010
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 117:6, s. 3601-3609
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Tidskriftsartikel (refereegranskat)abstract
- Two types of microfibrillated cellulose (MFC) were prepared using either a sulfite pulp containing a high amount of hemicellulose (MFC 1) or a carboxymethylated dissolving pulp (MFC 2). MFC gels were then combined with amylopectin solutions to produce solvent-cast MFC-reinforced amylopectin films. Tensile testing revealed that MFC 2-reinforced films exhibited a more ductile behavior and that MFC 1-reinforced films had higher modulus of elasticity (E-modulus) at MFC loadings of 50 wt % or higher. Pure MFC films had relatively low oxygen permeability values when data were compared with those for a variety of other polymer films. MFC 1 and MFC 2 films had similar opacity but differences in appearance which were attributed to the presence of some larger fibers and nanofiber agglomerates in MFC 2. Field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were used to illustrate the morphology of MFC nanofibers in pure films and in an amylopectin matrix.
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| 2. |
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| 3. |
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| 4. |
- Aldaeus, Fredrik, et al.
(författare)
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Towards a cellulose-based society : current market and consumer trends
- 2017
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Ingår i: The 7th Nordic Wood Biorefinery Conference held in Stockholm, Sweden, 28-30 Mar. 2017. - Stockholm : RISE Bioekonomi. - 9789186018207 ; , s. 1-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It has been proposed that the future of the forest industry will involve the traditional value chains combined with the needs and demands of a bio-based economy. A global consumer survey was undertaken, together with interviews and workshops with various representatives through the bio-economy. Sources also included in-depth literature studies and research reviews. Based on this input, several current trends have been identified that will affect the route towards a cellulose-based society. These trends describe the effects of urbanization, consumer behaviour, new business models, material recycling, open innovation and the necessity for early demonstration of new research. Four different but equally plausible scenarios have been identified describing the society and the role of cellulose in 2030, highlighting the role of the wood-based biorefinery.
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| 5. |
- Aldaeus, Fredrik, et al.
(författare)
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Towards a cellulose-based society : current trends, future scenarios, and the role of the wood biorefinery
- 2016
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Ingår i: Proceedings of the 14th European workshop on lignocellulosics and pulp. - 9791090188020 ; , s. 125-127
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is a great need to maintain research for a future in which the traditional value chains of the forest industry are combined with the needs and demands of a bio-based economy. In such a future, the pulp mill biorefinery will be a crucial node. In order to map the transformation from a fossil-based society to a cellulose-based society, a global consumer survey has been made. In addition, interviews and workshops with various players throughout the bio-economy field have been accomplished. Several current trends that affect the road to a cellulose-based society have been identified. These trends are describing the effects of urbanization, consumer behaviour, new business models, material recycling, open innovation, and the need for early demonstration of new research. The trends have been combined with uncertainties into a number of plausible scenarios describing the society and the role of cellulose in the year 2030.
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| 6. |
- Cho, Sung-Woo
(författare)
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Aging and heat-sealing properties of films based on wheat gluten
- 2007
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recently the research interest of the possibility of using wheat gluten (WG) as packaging material has greatly increased due to its combination of high gas barrier, attractive mechanical, film-forming and renewable properties. The source is also readily available and inexpensive on a worldwide basis. The glycerol-plasticized WG films cast from pH 4 and pH 11 solutions were investigated in order to understand the mechanisms behind the undesired aging. The film prepared from the pH 11 solution was mechanically more stable upon aging than the pH 4 film, which was initially very ductile but turning brittle with time. It was revealed that the protein structure of the pH 4 film was initially less polymerized/aggregated and the polymerization increased during storage but it did not reach the degree of aggregation of the pH 11 film, whereas deamidation was occurred and increased in the pH 11 film. During aging, the pH 4 film lost more mass than the pH 11 film mainly due to migration of glycerol but also due to some loss of volatile mass and the greater plasticizer loss of pH 4 film was presumably due to its initial lower degree of protein aggregation /polymerization. The glycerol migration of cast films exposed to a porous paper was further investigated with respect to pH of cast solution, glycerol content and film thickness since it was the main reason for deterioration of the properties. The opacity was also characterized. The glycerol migration was quantified using GC method in order to determine only glycerol content, but not other volatile substances. Glycerol content did not significantly change the opacity and pH 4 films showed good contact clarity because of less Maillard reaction. Glycerol was extensively migrating to the paper support and the migration seemed to be diffusion controlled. The heat sealability of WG films was investigated, using an impulse-hear sealer. It was observed that the WG films were readily sealable keeping up their integrity. The sealing temperature had a negligible effect on the lap-shear strength, but the peel strength increased with sealing temperature. The lap-shear strength increased with increasing mold temperature and the failure mode changed.
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| 7. |
- Christiernin, M., et al.
(författare)
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The effects of xyloglucan on the properties of paper made from bleached kraft pulp
- 2003
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 18:2, s. 182-187
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Tidskriftsartikel (refereegranskat)abstract
- Xyloglucan was adsorbed onto bleached soft-wood kraft pulp followed by preparation and analysis of handsheets with respect to sheet formation as well as sheet mechanical and optical properties. Adsorption of xyloglucan was found to be slow. After more than 20 hrs adsorption, equilibrium had not been reached. The amount of xyloglucan adsorbed increased with beating, but neither the rate of adsorption nor the quantity adsorbed was significantly affected by temperature. Xyloglucan was found to be practically irreversibly adsorbed onto the fibres and the effects of xyloglucan on paper sheet properties were investigated after thorough washing of the pulp. The adsorption characteristics of xyloglucan confirm observations by other authors on other cellulose substrates. Tensile index values for handsheets formed with the xyloglucan-containing pulps were higher than those measured for control pulps with a comparable beating degree. The light scattering coefficient was, however, not affected by xyloglucan adsorption. Hence, the increase in tensile strength is attributed to an increased relative bond strength between the fibres. Tensile strength versus tear strength relationship was similar for pulps with and without xyloglucan, but water retention value and dewatering resistance were lower for the xyloglucan treated pulps than for the reference pulps at the same tensile strength. In addition, formation was improved for pulps with adsorbed xyloglucan. The conclusion is that xyloglucan is a promising wet end additive that decreases the necessity for beating of the pulp and improves the formation of paper.
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| 8. |
- Ekevåg, Per, et al.
(författare)
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Addition of carboxymethylcellulose to the kraft cook
- 2004
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 19:2, s. 200-207
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Tidskriftsartikel (refereegranskat)abstract
- The physical attachment of carboxymethylcellulose (CMC) onto kraft pulps during cooking and the effects of subsequent bleaching in an OD(EOP)DD sequence were investigated. Two CMC grades with different molecular weights and different degrees of substitution (D.S.) were used, CMC Finnfix WRH and CMC Cekol DVG. The effect of the CMC was studied by measuring the increase in the total charge density as well as in the surface charge density. In this way, both the total amount of attached CMC and the amount of the CMC attached onto the surface of the fibres Could be determined. Hand-sheets were made to study the effects of CMC addition on the physical properties of the paper. Different amounts of CMC were added to find the optimum, which was determined to be 1% CMC on wood. The proportion of CMC attached at a level addition of 1% (on wood) was about 40%. It was, however, found that a large part of the CMC was degraded during the cook. Whereas high molecular weight CMC is attached onto the surface of fibres, the degraded CMC is attached to the interior of the cell wall, decreasing the efficiency of the CIVIC to enhance the joint strength between fibres. The tensile index increased significantly, approximately 10% after beating to 2000 PFI revolutions, when 1% CMC Finnfix WRH on wood was added. The CMC Cekol DVG grade showed the greatest increase in tensile index, approximately 12% at 2000 PFI revolutions. The results of the bleaching of a sample treated with CMC Finnfix WRH showed that a part of the effect of CMC remains after bleaching. Most of the reduction in the positive effect was due to a loss of CMC molecules from the fibre surface.
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| 9. |
- Helander, Mikael, et al.
(författare)
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Parameters Affecting the Cross-flow Filtration of Dissolved LignoBoost Kraft Lignin
- 2015
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Ingår i: Journal of wood chemistry and technology. - : Taylor & Francis Group. - 0277-3813 .- 1532-2319. ; 36:1, s. 1-8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In the kraft pulping process, the lignin-containing by-product kraft black liquor is currently combusted as an energy source. LignoBoost is a technique that extracts lignin from kraft black liquor, resulting in a lignin-lean black liquor, which is returned to the process, and an extracted kraft lignin. To facilitate the use of the extracted kraft lignin in high-value applications, it can be refined via fractionation to produce a more homogeneous starting raw material. Hence, the aim of this study is to investigate the behavior of dissolved softwood kraft lignin during cross-flow filtration. The effects of the lignin concentration, pH, and ionic strength on the fractionation of the dissolved lignin during cross-flow filtration are investigated. The results indicate that large amounts of low-molecular-weight kraft lignin can be produced from solutions having a low lignin concentration. Furthermore, the effects of pH and ionic strength on the fractionation of low-molecular-weight lignin are identified within the studied ranges.
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| 10. |
- Henningsson, Susanne, 1977, et al.
(författare)
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Sex steroid-related genes and male-to-female transsexualism
- 2005
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Ingår i: Psychoneuroendocrinology. - Oxford : Pergamon Press. - 0306-4530 .- 1873-3360. ; 59:5, s. 412-412
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Tidskriftsartikel (refereegranskat)abstract
- Transsexualism is characterised by Lifelong discomfort with the assigned sex and a strong identification with the opposite sex. The cause of transsexualism is unknown, but it has been suggested that an aberration in the early sexual differentiation of various brain structures may be involved. Animal experiments have revealed that the sexual differentiation of the brain is mainly due to an influence of testosterone, acting both via androgen receptors (ARs) and-after aromatase-catalyzed conversion to estradiol-via estrogen receptors (ERs). The present study examined the possible importance of three polymorphisms and their pairwise interactions for the development of male-to-female transsexualism: a CAG repeat sequence in the first exon of the AR gene, a tetra nucleotide repeat polymorphism in intron 4 of the aromatase gene, and a CA repeat polymorphism in intron 5 of the ER beta gene. Subjects were 29 Caucasian male-to-female transsexuals and 229 healthy mate controls. Transsexuals differed from controls with respect to the mean Length of the ER repeat polymorphism, but not with respect to the length of the other two studied polymorphisms. However, binary logistic regression analysis revealed significant partial effects for all three polymorphisms, as well as for the interaction between the AR and aromatase gene polymorphisms, on the risk of developing transsexualism. Given the small number of transsexuals in the study, the results should be interpreted with the utmost caution. Further study of the putative role of these and other sex steroid-related genes for the development of transsexualism may, however, be worthwhile.
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| 11. |
- Kanellis, Dimitris C., et al.
(författare)
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The exon-junction complex helicase eIF4A3 controls cell fate via coordinated regulation of ribosome biogenesis and translational output
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:32
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic initiation factor 4A-III (eIF4A3), a core helicase component of the exon junction complex, is essential for splicing, mRNA trafficking, and nonsense-mediated decay processes emerging as targets in cancer therapy. Here, we unravel eIF4A3's tumor-promoting function by demonstrating its role in ribosome biogenesis (RiBi) and p53 (de)regulation. Mechanistically, eIF4A3 resides in nucleoli within the small subunit processome and regulates rRNA processing via R-loop clearance. EIF4A3 depletion induces cell cycle arrest through impaired RiBi checkpoint-mediated p53 induction and reprogrammed translation of cell cycle regulators. Multilevel omics analysis following eIF4A3 depletion pinpoints pathways of cell death regulation and translation of alternative mouse double minute homolog 2 (MDM2) transcript isoforms that control p53. EIF4A3 expression and subnuclear localization among clinical cancer specimens correlate with the RiBi status rendering eIF4A3 an exploitable vulnerability in high-RiBi tumors. We propose a concept of eIF4A3's unexpected role in RiBi, with implications for cancer pathogenesis and treatment.
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| 12. |
- Lindström, Jonas, 1977-, et al.
(författare)
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Uppgifter om mäns och kvinnors försörjningsaktiviteter i häradsrättens protokoll, Snevringe (Västmanland), perioden 1720-1880
- 2020
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Annan publikationabstract
- Uppgifter om mäns och kvinnors försörjningsaktiviteter i Snevringe (Västmanland) häradsrätts protokoll har transkriberats och analyserats, och källtext och källtrogna variabler registrerats bokstavstroget, av Jonas Lindström, Benny Jacobsson, Carl Mikael Carlsson, Karin Hassan Jansson, Linnea Henningsson, Maria Ågren, Sarah Vorminder och Örjan Kardell, inom forskningsprojektet Gender and Work.Kvalitetskontroll är utförd av Sofia Ling och Jonas Lindström.Analys av källmaterialet har gjorts av Benny Jacobsson, Carl Mikael Carlsson, Karin Hassan Jansson, Linnea Henningsson, Maria Ågren, Sarah Vorminder, Örjan Kardell inom projektet Gender and Work https://www.uu.se/gawMaterialet är sökbart i databasen GAW - https://gotham.ddb.umu.se/
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| 13. |
- Lindström, John, et al.
(författare)
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Zero Defect Manufacturing in an Industry 4.0 Context : A Case Study of Requirements for Change and Desired Effects
- 2020
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Ingår i: TESConf 2020 - 9th International Conference on Through-life Engineering Services. - : Elsevier BV.
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Konferensbidrag (refereegranskat)abstract
- The paper addresses, based on a case study comprising six process- and manufacturing industry companies, requirements for change and desired effects from Zero Defect Manufacturing in an Industry 4.0 context. The results outline seven problems and five needs perceived by the companies. Further, the results also outline four desired effects. The results are aligned with existing literature and studies but also bring up new aspects of Zero Defect Manufacturing in terms of problems, needs and desired effects. Noteworthy new desired effects are increased trust for the production process and improved gender equality.
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| 14. |
- Lindström, Leif, et al.
(författare)
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Maintenance therapy with second generation antipsychotics for bipolar disorder - A systematic review and meta-analysis
- 2017
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Ingår i: Journal of Affective Disorders. - : ELSEVIER SCIENCE BV. - 0165-0327 .- 1573-2517. ; 213, s. 138-150
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Forskningsöversikt (refereegranskat)abstract
- Background: Second generations antipsychotics (SGA) are frequently used for maintenance treatment in bipolar disorder. We systematically reviewed the efficacy and long-term effects of treatment with SGA, regardless of treatment strategy (SGA administered either as monotherapy or as adjunctive therapy), in comparison to placebo, lithium or valproate. Primary outcomes were relapses (mood episode recurrence) and discontinuation. Method: Clinical studies were identified through database searching in PubMed, Embase, PsychInfo and Cochrane Library and critically appraised based on the Cochrane Handbook. Full data extraction of raw data was performed and analyzed with meta-analyses, and level of evidence graded using GRADE. Only randomized controlled studies (RCT) and observational studies were included, with a minimum follow-up of 6 months. Comparators used were restricted to placebo, lithium, valproate or other anti-epileptic drugs. Results: We identified 15 RCTs on SGA in bipolar disorder with follow-up-time of 6 months up to 2 years, and one observational study reporting long-term effects of up to 4 years. A total of 6142 patients were included in the randomized trials. No long-term RCTs beyond 2 years follow-up was identified. All RCTs except for one included patients with bipolar disorder type I only. All RCTs except for two included patients pre-stabilized on the drug under investigation prior to randomization (enrichment design). For SGA as adjunctive therapy to lithium or valproate, meta-analyses showed that treatment with either aripiprazole (RR: 0.65, 95% CI 0.50-0.85), quetiapine (RR: 0.38, 95% CI 0.32-0.46) or ziprasidone (RR: 0.62, 95% CI 0.40-0.96) reduced the overall risk of relapses in patients that had responded during the stabilization phase. Adjunctive therapy with quetiapine was the only drug that reduced both manic and depressive episodes. For SGA as monotherapy, only quetiapine was shown to be better than lithium/ valproate for both manic and depressive relapses, but only for patients stabilized on quetiapine during the acute phase. As monotherapy, olanzapine, quetiapine and risperidone were shown to be superior to placebo in reducing the overall risk of relapses. Limitations: There were considerable limitations to the evidence base of maintenance treatment with SGA in bipolar disorder. Most studies used stabilized patients, i.e. enrichment design (selection bias), had considerable dropout levels (attrition bias), and variable degree of reporting bias. No long-term RCT data on efficacy is available beyond 2 years, and almost all studies are on bipolar disorder type I patients only. Despite these limitations, we elucidate quantitative findings from meta-analyses conducted on the randomized trials published on the topic.
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| 15. |
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| 16. |
- Siró, I., et al.
(författare)
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Highly Transparent Films from Carboxymethylated Microfibrillated Cellulose : The Effect of Multiple Homogenization Steps on Key Properties
- 2011
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Ingår i: Journal of Applied Polymer Science. - : Wiley-Blackwell. - 0021-8995 .- 1097-4628. ; 119:5, s. 2652-2660
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Tidskriftsartikel (refereegranskat)abstract
- We produced microfibrillated cellulose by passing carboxymethylated sulfite-softwood-dissolving pulp with a relatively low hemicellulose content (4.5%) through a high-shear homogenizer. The resulting gel was subjected to as many as three additional homogenization steps and then used to prepare solvent-cast films. The optical, mechanical, and oxygen-barrier properties of these films were determined. A reduction in the quantity and appearance of large fiber fragments and fiber aggregates in the films as a function of increasing homogenization was illustrated with optical microscopy, atomic force microscopy, and scanning electron microscopy. Film opacity decreased with increasing homogenization, and the use of three additional homogenization steps after initial gel production resulted in highly transparent films. The oxygen permeability of the films was not significantly influenced by the degree of homogenization, whereas the mean tensile strength, modulus of elasticity, and strain at break were increased by two or three extra homogenization steps.
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| 17. |
- Almgren, Karin M., et al.
(författare)
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Effects of Moisture on Dynamic Mechanical Properties of Wood Fiber Composites Studied by Dynamic FT-IR Spectroscopy
- 2008
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Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 27:16-17, s. 1709-1721
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Tidskriftsartikel (refereegranskat)abstract
- Wood fiber reinforced polylactide is a biodegradable composite where both fibers and matrix are from renewable resources. In the development of such new materials, information on mechanical behavior on the macroscopic and the molecular level is useful. In this study, dynamic Fourier transform infrared (FT-IR) spectroscopy is used to measure losses at the molecular level during cyclic tensile loading for bonds that are characteristic of the cellulosic fibers and the polylactid matrix. This molecular behavior is compared with measured macroscopic hysteresis losses for different moisture levels. The results show that moisture ingress will transfer the load from the fibers to the matrix, and that a more efficient fiber-matrix interface would diminish mechanical losses. Although the dynamic FT-IR spectroscopy method is still qualitative, this investigation shows that it can provide information on the stress transfer of the constituents in wood fiber reinforced plastics.
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| 18. |
- Almgren, Karin M., et al.
(författare)
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Moisture uptake and hygroexpansion of wood fiber composite materials with polylactide and polypropylene matrix materials
- 2009
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 30:12, s. 1809-1816
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Tidskriftsartikel (refereegranskat)abstract
- Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA-modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out-of-plane hygroexpansion of PLA and PLA/PP composites, under water-immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA-modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out-of-plane hygroexpansion, with a high-fiber fraction leading to large hygroexpansion. Fiber-matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake. POLYM. COMPOS., 30:1809-1816, 2009.
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| 19. |
- Almgren, Karin, et al.
(författare)
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Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets.
- 2009
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier BV. - 0143-7496 .- 1879-0127. ; 29:5, s. 551-557
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Tidskriftsartikel (refereegranskat)abstract
- Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.
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| 20. |
- Aminzadeh, Selda, 1984, et al.
(författare)
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Membrane filtration of kraft lignin: Structural charactristics and antioxidant activity of the low-molecular-weight fraction
- 2018
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Ingår i: Industrial Crops and Products. - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 112, s. 200-209
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Tidskriftsartikel (refereegranskat)abstract
- Lignin, which is the second most abundant biomass component and has carbon-rich phenolic content, is a promising renewable raw material for multiple applications, such as carbon fibers, adhesives, and emulsifiers. To use lignin efficiently, it is important to ensure its purity and homogeneity. As a result, the separation of lignin into fractions with high purity and narrow molecular-weight distributions is likely a prerequisite for several applications. Ultrafiltration using ceramic membranes has many advantages, including enabling direct lignin extraction from Kraft pulp cooking liquors without pH and temperature adjustment. One challenge with membrane filtration using such a system is the potential for reduced membrane performance over time, which is associated with fouling. In this study, LignoBoost Kraft lignin was fractionated using a ceramic membrane with a molecular weight cut-off of 1 kDa. The separation behavior during ultrafiltration fractionation was investigated and the antioxidant properties of the recovered low-molecular-weight (low-MW) lignin samples were evaluated. Using this model system, the permeate fluxes were unstable during the 100 h of membrane operation. However, a decrease in the average MW in the permeate over time was observed. The shift in MW was most pronounced for virgin membranes, while a more stable MW distribution was evident for membranes subjected to multiple cleaning cycles. According to 2D NMR analysis, low-MW lignin that was recovered after 100 h of operation, consisted of smaller lignin fragments, such as dimers and oligomers, with a high content of methoxy-groups. This was confirmed using the size exclusion chromatography method, which indicated an weigh average molecular weight in the range of 450–500 Da. 31P NMR spectroscopy showed that, despite the lower total content of phenolic OH groups, the low-MW sample had a higher proportion of non-condensed phenolic OH groups. The results of the antioxidant tests demonstrated the strong potential of lignin and its low-MW fraction as a natural antioxidant, particularly for lipid-containing systems. The low-MW lignin fraction showed better antioxidant activity than the non-fractionated LignoBoost lignin in the kinetic oxygen radical absorbance capacity (ORAC) test and demonstrated three-fold stronger inhibition of the substrate (fluorescein) than the reference antioxidant Trolox (a water-soluble derivative of vitamin E).
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| 21. |
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| 22. |
- Aminzadeh, Selda
(författare)
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Valorization of Kraft Lignin by Fractionation and Chemical Modifications for Different Applications
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- AbstractLignin is one of the most abundant biopolymers. Approximately 70 million tons of technical lignin is generated annually, but only little is used for products other than energy. The complexity of lignin hinders full utilization in high-value products and materials. In spite of the large recent progress of knowledge of lignin structure and biosynthesis, much is still not fully understood, including structural inhomogeneity. We made synthetic lignin at different pH’s and obtained structural differences that might explain the structural inhomogeneity of lignin.Technical lignins from the chemical pulping are available in large scale, but the processes result in alterations, such as oxidation and condensation. Therefore, to utilize technical lignin, modifications, such as fractionation and/or chemical modifications are necessary. Fractionation with ceramic membranes is one way to lower the polydispersity of lignin. The main advantage is their tolerance towards high temperature and harsh conditions. We demonstrated that low Mw lignin was extracted from industrially produced LignoBoost lignin aiming: i) to investigate the performance of the membrane over time; ii) to analyze the antioxidant properties of the low Mw lignin.Chemical modification can also improve the properties of lignin. By adding moieties, different properties can be obtained. Amination and methacrylation of kraft lignin were performed, as well as lignin-silica hybrid materials with potential for the adsorption were produced and investigated.Non-modified and methacrylated lignin were used to synthesize lignin-St-DVB porous microspheres to be utilized as a sorbent for organic pollutants. The possibility to substitute styrene with methacrylated lignin was evaluated, demonstrating that interaction between lignin and DVB, and porosity increased.Lignin has certain antibacterial properties. Un-modified and modified (aminated) lignin samples and sphere nanoparticles of lignin were tested for their effect against gram-positive and gram-negative bacteria’s and an injectable hydrogel was developed with encapsulated lignin for being used as an injectable gel for the open wounds. Results demonstrated promising antibacterial efficiency of lignins against gram-positive, more especially better inhibition with aminated lignins against gram-positive and negative bacterium.
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| 23. |
- Amundin, Mats, 1947-, et al.
(författare)
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An echolocation visualization and interface system for dolphin research
- 2008
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 123:2, s. 1188-1194
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Tidskriftsartikel (refereegranskat)abstract
- The present study describes the development and testing of a tool for dolphin research. This tool was able to visualize the dolphin echolocation signals as well as function as an acoustically operated "touch screen." The system consisted of a matrix of hydrophones attached to a semitransparent screen, which was lowered in front of an underwater acrylic panel in a dolphin pool. When a dolphin aimed its sonar beam at the screen, the hydrophones measured the received sound pressure levels. These hydrophone signals were then transferred to a computer where they were translated into a video image that corresponds to the dynamic sound pressure variations in the sonar beam and the location of the beam axis. There was a continuous projection of the image back onto the hydrophone matrix screen, giving the dolphin an immediate visual feedback to its sonar output. The system offers a whole new experimental methodology in dolphin research and since it is software-based, many different kinds of scientific questions can be addressed. The results were promising and motivate further development of the system and studies of sonar and cognitive abilities of dolphins. © 2008 Acoustical Society of America.
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| 24. |
- Andersson, Alexander, et al.
(författare)
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Presence of Calcium Cations Stimulate Alkaline Hydrolysis of Cellulose During Kraft Pulping Conditions
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Simulated kraft pulping has been performed on cotton linters fibers consisting of almost pure cellulose with varying content of calcium ions. These concentrations were obtained by soaking and drying cotton linters in calcium sulfate solutions. The viscosities of the pulped fibers were generally lower with higher calcium ion concentration and, therefore, in line with earlier suggested ideas that calcium ions could catalyze alkaline hydrolysis. The technical importance of these results is discussed.
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| 25. |
- Andersson, Rasmus
(författare)
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Evaluation of two hydrocyclone designs for pulp fractionation
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The process conditions and fractionation efficiency of two hydrocyclone designs, a novel and a conventional conical design, were evaluated. The novel design comprised a modified inlet section, where the pulp suspension had to pass a narrow ring-shaped opening, and a very compact fractionation zone. The influence of feed concentration and fine fraction mass ratio was studied. The trials were performed with never-dried, unrefined bleached chemical softwood pulp. Fractionation efficiency was evaluated in terms of change of surface roughness of handsheets made out of the fractions and the feed pulp respectively.The fractionation efficiency increased considerably with decreasing fine fraction mass ratio, especially at higher feed concentrations. This finding prompted a hypothesis on the existence of a radial gradient in the composition of the suspension inside the novel hydrocyclone. Using the novel hydrocyclone in a feed-forward fractionation system would therefore prove to be more favourable as a larger total fine fraction of better properties can be obtained. A three-stage feed-forward fractionation system was evaluated in laboratory scale. Here, it was indeed possible to extract fine fractions with improved surface properties in each of the three consecutive stages. All three fine fractions had about the same surface roughness.The fractionation performance of the novel design was benchmarked against that of a conventional, best available technology (BAT) design. In terms of fractionation efficiency, the BAT design performed better. However, the fractions produced with the novel hydrocyclone had a much smaller difference in concentration, implying a much less pronounced enrichment of fines in the fine fraction. It is unclear, to what extent the lower share of latewood fibres and the increased fines content, respectively, contributed to the improved surface roughness of the fine fractions. However, it is clear that the lower enrichment of fines in the novel hydrocyclone makes it easier to install it in industrial applications without a need for auxiliary equipment to redistribute large water flows.
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| 26. |
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| 27. |
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| 28. |
- Ankerfors, Mikael, et al.
(författare)
-
Method for providing a nanocellulose involving modifying cellulose fibers
- 2009
-
Patent (populärvet., debatt m.m.)abstract
- The present invention provides a method for the manufacturing of nanocellulose. The method includes a first modification of the cellulose material, where the cellulose fibres are treated with an aqueous electrolyte-containing solution of an amphoteric cellulose derivative. The modification is followed by a mechanical treatment. By using this method for manufacturing nanocellulose, clogging of the mechanical apparatus is avoided. Also disclosed is nanocellulose manufactured in accordance with said method and uses of said cellulose.
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| 29. |
- Ankerfors, Mikael, et al.
(författare)
-
Multilayer assembly onto pulp fibres using oppositely charged microfibrillated celluloses, starches, and wetstrength resins : Effect on mechanical properties of CTMP-sheets
- 2016
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 31:1, s. 135-141
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of multilayering of microfibrillar cellulose (MFC) onto a chemi-thermomechanical pulp (CTMP), from which the fines material had been removed, were investigated with regard to the mechanical properties of hand-sheets. In one series of experiments, the CTMP was multilayered with cationic MFC/anionic MFC (C-MFC/A-MFC) at various addition levels and sheets made in a conventional sheet former, pressed, and dried at room temperature. This experimental series was complemented with a second series, where sheets were made in a Rapid Köthen sheet former. In a third series of experiments, the CTMP was multilayered using a cationic polyamideamine epichlorohydrine resin (PAE) and an AMFC. Sheets were formed using the Rapid Köthen sheet former. Finally, in a fourth series of experiments, the MFC multilayering experiments were compared with multilayering experiments using cationic starch/anionic starch (C-starch/A-Starch). MFC-multilayering (C-MFC/A-MFC) gave inferior strength gain at a low addition level compared to starch multilayering, but (compared on a weight basis) the strength seemed to level off using starches at high addition levels, whereas there were a continuous increase in strength using MFC multilayering. Multilayering using PAE/A-MFC was found to give a higher strength gain than both C-MFC/A-MFC and C-starch/A-starch multilayering. Sheet density was slightly affected (<14%) by the multilayering techniques used in these experiments.
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| 30. |
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| 31. |
- Ankerfors, Mikael, et al.
(författare)
-
The effects of different types of wet-end added microfibrillated celluloses on the properties of paper made from bleached kraft pulp
- 2017
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 32:3, s. 336-345
-
Tidskriftsartikel (refereegranskat)abstract
- Research has been undertaken to compare the effects of different types of microfibrillated cellulose (MFC) on the mechanical properties of paper. Three types of MFC were produced: Enzyme MFC (low anionic charge density), Carboxymethylated MFC (high anionic charge density) and cationic MFC (high cationic charge density). The different MFCs required different retention aid strategies. The simplest retention strategy was selected to secure a high retention of MFC. Some experiments also focused on dewatering and pressability of wet webs with carboxymethylated MFC. Conventional isotropic laboratory handsheets were made using a never-dried unrefined elemental chlorine free (ECF)-bleached softwood kraft pulp. It has been shown that the evolution of the mechanical properties and scattering coefficients when plotted versus MFC content was very similar for the three types. However, Enzyme MFC gave a significantly better reinforcement effect. All three types of MFC had a similar effect on the sheet consolidation, reflected in sheet density. Evaluation of the dewatering and pressability of the wet sheets showed that if the MFC was aggregated by an appropriate retention strategy, the dewatering and pressability were not detrimental to the practical applicability of MFC.
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| 32. |
- Ankerfors, Mikael, et al.
(författare)
-
The use of microfibrillated cellulose in fine paper manufacturing : Results from a pilot scale papermaking trial
- 2014
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 29:3, s. 476-483
-
Tidskriftsartikel (refereegranskat)abstract
- In this work the strength enhancing capabilities of microfibrillated cellulose (MFC) in highly filled papers was studied. Both the MFC production and the paper making were done in pilot scale under realistic industrial conditions. The results clearly show that MFC (2.5-5.0 wt-%) could improve the mechanical properties of highly filled papers (20-35 wt-% filler contents). All studied dry mechanical properties were improved and the improvements were most pronounced for Z-strength and fracture toughness. By combining the MFC with a C-starch dosage further improvements in mechanical properties could be achieved. The improvements in mechanical properties enabled increased filler content with retained properties. The filler increase could be achieved at the same time as the sheet formation and the dry content after pressing were improved.
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| 33. |
- Ankerfors, Mikael, et al.
(författare)
-
Topo-chemical modification of fibres by grafting of carboxymethyl cellulose in pilot scale
- 2013
-
Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; :1, s. 6-14
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to graft carboxymethyl cellulose (CMC) on to bleached softwood kraft pulp at temperatures below 100°C and to do a pilot paper machine trial in order to examine the influence of the CMC on dewatering, sheet formation and mechanical properties. During the pilot trial, one CMC grafted pulp was compared to a pulp with 3 different refining degrees. It was shown that CMC-grafting improves the mechanical properties of paper with only a minor effect on the sheet density. It was also shown that the CMC grafting is less detrimental to dewatering than refining and at a certain tensile index a higher dry content after pressing could be reached. The formation number of the paper produced in the FEX trial was not significantly affected by the addition of CMC.
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| 34. |
- Antonsson, S., et al.
(författare)
-
A comparative study of the impact of the cooking process on oxygen delignification
- 2003
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 18:4, s. 388-394
-
Tidskriftsartikel (refereegranskat)abstract
- The impact of oxygen delignification on chemical pulps of a given kappa number manufactured in different ways (using kraft, prehydrolysis kraft and magnesium sulphite cooking) has been investigated. The prehistory of the pulps proves to be a very important factor in determining the response to oxygen delignification, i.e. the degree of delignification. It is shown that this is not due to different amounts of hexenuronic acid (HexA) in the different pulps, although this is an important factor behind the high residual kappa number after oxygen delignification of birch kraft pulp. Oxygen delignification of sulphite pulps proves to be efficient even at kappa numbers significantly lower than 10. These pulps show the greatest yield loss over the oxygen delignification. It is likely that Lignin Carbohydrate Complexes (LCC) complexes play a very important role in limiting the speed of reaction of oxygen delignification. Due to the very different prehistories of the pulps investigated, it is probable that the LCC:s are native and not formed during cooking.
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| 35. |
- Antonsson, Stefan, et al.
(författare)
-
Adding lignin derivatives to decrease the effect of mechano-sorptive creep in linerboard
- 2008
-
Ingår i: Appita journal. - 1038-6807. ; 61:6, s. 468-471
-
Tidskriftsartikel (refereegranskat)abstract
- When load is applied to any type of paper while varying the relative humidity, the paper will creep more than if the same load is applied at constant humidity. This behaviour is called mechano-sorptive creep or accelerated creep, and the reasons for its occurrence in paper are still not fully understood. However, wet strength and the addition of apolar (hydrophobic) compounds to sheets have previously been suggested as factors improving the mechano-sorptive creep performance. This work evaluates a method for improving wet strength and tests the addition of a hydrophobic compound, with particular reference to mechano-sorptive creep stiffness. Wet strength was improved by subjecting kraft liner pulp to low-molecular-weight lignin, obtained by cross-flow filtration, and to the radical initiator manganese(III). The hydrophobic compound added was a suberin-like lignin derivative. Adding the suberin-like lignin derivative significantly increased the mechano-sorptive creep stiffness, even though the stiffness at 90% rh decreased in the tested samples. This was probably because of the decrease in hygroexpansion caused by this hydrophobic additive. Even though it is possible significantly to increase the wet strength of kraft liner pulp by adding manganese(III) and cross-flow-filtered lignin, doing so has no significant effect on mechano-sorptive creep stiffness.
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| 36. |
- Antonsson, Stefan, et al.
(författare)
-
Applying a novel cooking technique to produce high kappa number pulps : the effects on physical properties
- 2009
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:4, s. 415-420
-
Tidskriftsartikel (refereegranskat)abstract
- A recently developed kraft cooking technique, with a longer impregnation time at lower temperatures to facilitate diffusion over consumption of active cooking chemicals, makes it possible to produce kraftliner pulp without inline refining. This technique was applied to prepare two pulps with different lignin contents, which were compared with two industrial pulps from conventional kraft cooks in order to evaluate the physical properties of the pulps. It was demonstrated that pulps with lower lignin content can increase tensile stiffness, decrease hygroexpansion, and decrease the mechano-sorptive creep of handsheets. However, no difference in SCT and tensile energy absorption values due to different lignin contents was observed. It was further demonstrated that pulps made with Extended Impregnation Cooking (EIC) results in straighter pulp fibres with higher cellulose content. These pulps tended to have lower mechano-sorptive creep than conventional pulps. A higher brightness of the pulp sheets can also be obtained by choosing a higher alkali profile.
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| 37. |
- Antonsson, Stefan, et al.
(författare)
-
Biomimetic synthesis of suberin for new biomaterials
- 2005
-
Ingår i: Appita Annual Conference. ; , s. 561-564
-
Konferensbidrag (refereegranskat)abstract
- Suberin is the biopolymer giving cork (oak bark) its hydrophobic and resistant characteristics. It acts as a diffusion barrier in bark and roots of plants. Similarly to lignin, it is a phenolic polymer with good affinity to cellulose and other wood polysaccharides, but it also contains polyaliphatic and strongly hydrophobic elements. In order to produce a lignin derivative similar to suberin, a desired lignin starting material should be of low molecular weight and have a high content of hydroxylic phenolic groups. By means of cross flow nanofiltration of softwood kraft pulping black liquor and pH-precipitation with diluted sulphuric acid, such a lignin has been obtained. Due to the fact that too much organics entering the recovery boiler frequently is the bottleneck for pulp production increases, a removal of part of the lignin can be economically very favourable. By using this lignin together with linola oil, a linseed oil with a large amount of unsaturated structures, an attempt was made to create a new hydrophobic lignin derivative similar tosuberin. The product was analysed with FT-IR, Fourier Transformed Infra Red Spectroscopy and GPC, Gel Permeation Chromatography. The suberin like material obtained from this lignin could be polymerised on thermo mechanical pulp fibres by means of Mn(III)-driven phenolic coupling. The ability of the suberin monomers to act as a hydrophobic paper coating was evaluated with contact angle measurements and the results indicate that this lignin derivative was potentially of interest due to its capability to interact well with wood fibres and make paper hydrophobic.
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| 38. |
- Antonsson, Stefan, et al.
(författare)
-
Comparison of the physical properties between hardwood and softwood pulps
- 2009
-
Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 24:4, s. 409-414
-
Tidskriftsartikel (refereegranskat)abstract
- High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechano-sorptive creep properties.The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps.The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.
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| 39. |
- Antonsson, Stefan, et al.
(författare)
-
Low Mw-lignin fractions together with vegetable oils as available oligomers for novel paper-coating applications as hydrophobic barrier
- 2008
-
Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 27:1, s. 98-103
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin residues are available in large amounts as kraft lignin from chemical pulping processes. This lignin is mainly incinerated in recovery boilers. The recovery boilers are often the bottle-necks in the overall pulping process when pulp production increases are desired. Through cross-flow nano-filtration of the black liquor from kraft pulping, a low-molecular weight lignin fraction can be removed thus decreasing the organic load on the recovery boilers. The low-molecular weight lignin fraction furthermore exhibit different characteristics compared to other commercial kraft lignins and represents a new raw material source in novel applications. The low-molecular weight lignin was used together with a vegetable oil to produce a new hydrophobic lignin derivative similar to suberin. The lignin and the lignin derivative was analysed with FT-IR, UV-vis and SEC. The ability of the product to make paper surfaces hydrophobic was also evaluated. The results demonstrate the possibility to make a suberin-like lignin derivative that is potentially of interest in paper-coating applications due to its capability to interact well with wood fibres and make paper hydrophobic.
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| 40. |
- Antonsson, Stefan, 1979-
(författare)
-
Strategies for improving kraftliner pulp properties
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A large part of the world paper manufacturing consists of production of corrugated board components, kraftliner and fluting, that are used in many different types of corrugated boxes. Because these boxes are stored and transported, they are often subjected to changes in relative humidity. These changes together with mechanical loads will increase the deformation of the boxes compared to the case where the same loads are applied in a static environment. This enlarged creep due to the changes in relative humidity is called mechano-sorptive or accelerated creep. Mechano-sorptive creep forces producers to use high safety factors when designing boxes, and therefore, this is one of the key properties of kraftliner boards. Different strategies to decrease mechano-sorptive creep, and to simultaneously gain more knowledge about the causes for this phenomenon in paper, are the aim of this work. Derivatised and underivatised black liquor lignins, a by-product produced in pulp mills in large quantities, have been used together with biomimetic methods, to modify the properties of kraftliner pulp. Furthermore, the properties of kraftliner pulp have been compared to other pulps in order to evaluate the influence of fibre morphological factors, such as fibre width and shape factor, on the mechano-sorptive creep. In addition the influence of the chemical composition of the kraftliner pulp has been evaluated both by means of treating a kraftliner pulp with chlorite and xylanase and by producing pulps with different chemical composition. By using lignin and biomimetic methods, to create radical coupling reactions, it has been shown that it is possible to increase the wet strength of kraftliner pulp sheets. This method of treating the pulp showed, however, no significant effects on the mechano-sorptive creep. The addition of an apolar suberin-like lignin derivative, which has been shown to be possible to produce from natural resources, did show a positive effect on mechano-sorptive creep properties, but at the expense of stiffness properties in constant climate. Different pulps were compared with a kraftliner pulp and it was observed that the ratio between tensile stiffness and hygroexpansion can be used to estimate the mechano-sorptive creep properties. The hardwood kraft pulps investigated had lower hygroexpansion, probably due to more slender and straighter fibres, and higher tensile stiffness, probably due to lower lignin content. As the lignin content was varied by different methods in kraft pulps, it was observed that increased lignin content gives an increased hygroexpansion and decreased tensile stiffness as well as an increased mechano-sorptive creep. There were also indications of increased mechano-sorptive creep due to higher xylan content.
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| 41. |
- Antonsson, Stefan, et al.
(författare)
-
The influence of lignin and xylan on some kraftliner pulp properties
- 2009
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 24:4, s. 403-408
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the influence of lignin and hemicellulose content on the mechanical and physical properties of softwood kraft liner pulp. Tensile properties, hygroexpansion, and mechano-sorptive creep properties were measured. The lignin and hemicellulose contents were modified by chlorite delignification and xylanase treatment. After treatment, the chemical composition of the pulps was 3-14% Klason lignin, 69-77% cellulose, 16-21% hemicellulose, and 4-7% xylan. In the tested pulps, low lignin content tended to decrease hygroexpansion as well as increase tensile stiffness and mechano-sorptive creep stiffness. Xylan contributed less to the pulp sheet properties, but at equal lignin contents, higher xylan content tended to give increased hygroexpansion and worse mechano-sorptive creep properties.
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| 42. |
- Antonsson, Stefan, et al.
(författare)
-
The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps
- 2010
-
Ingår i: Appita journal. - 1038-6807. ; 63:1, s. 231-
-
Tidskriftsartikel (refereegranskat)abstract
- Hygroexpansion coefficient and tensile stiffness are important parameters in many paper applications. This study compares several bleached industrial hardwood kraft pulps, comprising five eucalypt pulps from South America, Europe, and Africa as well as an acacia pulp from Asia and a birch pulp from Scandinavia. Refined and unrefined pulps are compared. The results indicate significant differences in hygroexpansion but smaller differences in tensile stiffness index at comparable densities. No single factor offering a reasonable explanation of these differences in hygroexpansion coefficient, such as carbohydrate composition, fibre dimensions, or fibre form, was found. However, correlation between hygroexpansion coefficient and the mechano-sorptive creep stiffness was observed. We suggest that the hygroexpansion coefficient at a given tensile stiffness level can be used to rank pulps in terms of their mechano-sorptive creep properties.
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| 43. |
- Antonsson, Stefan, 1979-
(författare)
-
The Use of Lignin Derivatives to Improve Selected Paper Properties
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ved består huvudsakligen av tre typer av polymerer, cellulosa, hemicellulosa och lignin. Lignin bildas i naturen genom enzymatiskt initierad oxidativ koppling av tre olika typer av fenylpropan-enheter. Dessa bygger genom olika kol-kol- och kol-syre-bindningar upp en amorf tredimensionell polymer. När kemisk massa tillverkas bryts lignin ner och löses ut i kokluten. Luten innehåller de förbrukade kokkemikalierna och bränns generellt i en sodapanna för att regenerera kemikalierna och producera ånga. Sodapannan är emellertid dyr. Därför har den blivit produktionsbegränsande på många massabruk. Att avlägsna en del av ligninet från avluten vore därför önskvärt och att finna ekonomiskt intressanta produkter baserade på lignin från svartlut är därför ett viktigt forskningsområde . Ett lämpligt område för ligninprodukter vore som tillsatts i oblekt massa. Oblekt massa används till stor del för tillverkning av kraftliner, topp- och bottenskikten på wellpapp. När lådor av wellpapp lagras i containrar som färdas över haven, förändras den relativa luftfuktigheten. Detta gör att lådorna kollapsar lättare än om de skulle ha lagrats vid konstant luftfuktighet, även en hög sådan. Detta är på grund av det så kallade mekanosorptiva- eller accelererade krypfenomenet. Genom tillsatts av våtstyrkemedel till kraftliner eller behandla den med hydrofoba ämnen, finns indikatoner på att mekanosorptiva effekten skulle kunna minska. För att försöka minska den effekten har ett lågmolekylärt kraftlignin, som utvunnits med hjälp av tvärsflödesfiltrering av svartlut och svavelsyrafällning, använts. Genom derivatisering av detta lignin med linolja erhölls ett hydrofobt ligninderivat som uppvisar strukturella likheter med biopolymeren suberin. När detta suberinlika ligninderivat tillsätts till massa verkar det mekanosorptiva krypet minska. När lågmolekylärt lignin används tillsammans med ligninradikalinitiatorerna lackas eller mangan(III) i kraftlinermassa erhålls dessutom en våtstyrka på ca 5% av torrstyrkan. Efter aminering av detta lignin gav en tillsatts till kraftlinermassan en våtstyrka på upp till 10% av torrstyrkan. Det finns indikationer på att det mekanosorptiva krypet samtidigt minskar när dessa behandlingar görs som ger upphov till ökad våtstyrka.
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| 44. |
|
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| 45. |
- Aulin, Christian, et al.
(författare)
-
Oxygen and oil barrier properties of microfibrillated cellulose films and coatings
- 2010
-
Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 17:3, s. 559-574
-
Tidskriftsartikel (refereegranskat)abstract
- The preparation of carboxymethylated microfibrillated cellulose (MFC) films by dispersion-casting from aqueous dispersions and by surface coating on base papers is described. The oxygen permeability of MFC films were studied at different relative humidity (RH). At low RH (0%), the MFC films showed very low oxygen permeability as compared with films prepared from plasticized starch, whey protein and arabinoxylan and values in the same range as that of conventional synthetic films, e.g., ethylene vinyl alcohol. At higher RH's, the oxygen permeability increased exponentially, presumably due to the plasticizing and swelling of the carboxymethylated nanofibers by water molecules. The effect of moisture on the barrier and mechanical properties of the films was further studied using water vapor sorption isotherms and by humidity scans in dynamic mechanical analysis. The influences of the degree of nanofibrillation/dispersion on the microstructure and optical properties of the films were evaluated by field-emission scanning electron microscopy (FE-SEM) and light transmittance measurements, respectively. FE-SEM micrographs showed that the MFC films consisted of randomly assembled nanofibers with a thickness of 5-10 nm, although some larger aggregates were also formed. The use of MFC as surface coating on various base papers considerably reduced the air permeability. Environmental scanning electron microscopy (E-SEM) micrographs indicated that the MFC layer reduced sheet porosity, i.e., the dense structure formed by the nanofibers resulted in superior oil barrier properties.
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| 46. |
- Axelsson, Patrik, et al.
(författare)
-
Condensation reactions of lignin during birch Kraft pulping as studied by thioacidolysis
- 2004
-
Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 30:12, s. 317-322
-
Tidskriftsartikel (refereegranskat)abstract
- The influences of kappa number and ionic strength during birch kraft cooking on the extent of lignin condensation have been studied using thioacidolysis and size exclusion chromatography. Thioacidolysis degrades alkyl-aryl ether bonds in lignin while leaving carbon-carbon and diaryl-ether bonds relatively intact. Therefore, the lignin structures not cleaved during thioacidolysis can be considered as relatively stable and may account,, for example,for the slow residual phase delignification in the kraft cook and for differences in bleachability. It was shown that condensed lignin structures are formed in the residual lignin during birch kraft cooking. The relative amount of such structures increased with decreasing kappa number or with increasing sodium ion concentration in the cook. These structures were also found in a xylan-lignin complex isolated from a birch kraft pulp. The condensed structures were only partly reactive during oxygen delignification.
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| 47. |
- Axelsson, Patrik, et al.
(författare)
-
Influence of the conditions during birch kraft cooking on unbleached brightness, and on ECF- and TCF-bleachability
- 2004
-
Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 19:3, s. 309-317
-
Tidskriftsartikel (refereegranskat)abstract
- The influences on ECF and TCF bleachability of the hydroxide ion, hydrogen sulphide ion and sodium ion concentrations as well as of the amount of dissolved wood components (DWC) in a birch kraft cook were investigated. The pulping was carried out using a so-called constant composition cooking technique, where a high liquor-to-wood ratio enables an almost constant concentration of the cooking chemicals during the entire cook. This cooking method also renders possible to vary each cooking variable separately. The pulps were oxygen-delignified and bleached in a D(EOP)DD and a Q(OP)Q(PO) sequence. The presence of DWC caused a significant rate increasing effect on the delignification. An increase in hydroxide ion concentration, an increase in hydrogen sulphide ion concentration or a decrease in sodium ion concentration improved both the ECF and the TCF bleachability, but the DWC had no significant effect on the bleachability. Further a correlation was found between the bleachability and the brightness of the oxygen-delignified pulp.
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| 48. |
- Axelsson, P., et al.
(författare)
-
Molecular mass distributions of lignin and lignin-carbohyd rate complexes in birch Kraft pulps : Changes caused by the conditions in the cook and their relation to unbleached pulp brightness and bleachability
- 2005
-
Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 31:1, s. 19-27
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin-carbohydrate complexes and their relationship to pulp bleachability and unbleached pulp brightness were studied in four birch kraft pulps produced at high and low hydroxide ion and sodium ion concentrations, using size-exclusion chromatography (SEC). About 75-80%of the lignin was found to be associated with carbohydrates, a larger part with hemicelluloses and a smaller part with cellulose. Easily bleached pulps, produced under high [OH-] or low [Na+] conditions, had more lignin associated with cellulose than their counterparts. Furthermore, a high [OH-] gave a residual lignin that was significantly more accessible in the residual lignin isolation, and where the inaccessible lignin was bonded to carbohydrates. Colour differences of pulps caused by variations in the cooking conditions, as studied in the SEC system, were associated with all the lignin, irrespective of whether it was associated with hemicelluloses or cellulose.
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| 49. |
|
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| 50. |
- Azhar, Shoaib, 1980-, et al.
(författare)
-
Extraction of hemicelluloses from fiberized spruce wood
- 2015
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 117, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- A novel mechanical pre-treatment method was used to separate the wood chips into fiber bundles in order to extract high molecular weight wood polymers. The mechanical pre-treatment involved chip compression in a conical plug-screw followed by defibration in a fiberizer. The fiberized wood was treated with hot water at various combinations of time and temperature in order to analyze the extraction yield of hemicelluloses at different conditions. Nearly 6 mg/g wood of galactoglucomannan was obtained at 90◦C/120min which was about three times more than what could be extracted from wood chips. The extracted carbohydrates had molecular weight ranging up to 60 kDa. About 10% of each of the extracted material had a molecular weight above 30 kDa. The extraction liquor could also be reused for consecutive extractions with successive increase in the extraction yield of hemicelluloses.
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