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  • 1.
    Bengtsson, Andreas
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Carbon fibres from lignin-cellulose precursors2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is in the nature of the human species to find solutions of complex technical problems and always strive for improvements. The development of new materials is not an exception. One of the many man-made materials is carbon fibre (CF). Its excellent mechanical properties and low density have made it attractive as the reinforcing agent in lightweight composites. However, the high price of CF originating from expensive production is currently limiting CF from wider utilisation, e.g. in the automotive sector.

     

    The dominating raw material used in CF production is petroleum-based polyacrylonitrile (PAN). The usage of fossil-based precursors and the high price of CF explain the strong driving force of finding cheaper and renewable alternatives. Lignin and cellulose are renewable macromolecules available in high quantities. The high carbon content of lignin is an excellent property, while its structural heterogeneity yields in CF with poor mechanical properties. In contrast, cellulose has a beneficial molecular orientation, while its low carbon content gives a low processing yield and thus elevates processing costs.

     

    This work shows that several challenges associated with CF processing of each macromolecule can be mastered by co-processing. Dry-jet wet spun precursor fibres (PFs) made of blends of softwood kraft lignin and kraft pulps were converted into CF. The corresponding CFs demonstrated significant improvement in processing yield with negligible loss in mechanical properties relative to cellulose-derived CFs. Unfractionated softwood kraft lignin and paper grade kraft pulp performed as good as more expensive retentate lignins and dissolving grade kraft pulp, which is beneficial from an economic point of view.

     

    The stabilisation stage is considered the most time-consuming step in CF manufacturing. Here it was shown that the PFs could be oxidatively stabilised in less than 2 h or instantly carbonised without any fibre fusion, suggesting a time-efficient processing route. It was demonstrated that PF impregnation with ammonium dihydrogen phosphate significantly improves the yield but at the expense of mechanical properties.

     

    A reduction in fibre diameter was beneficial for the mechanical properties of the CFs made from unfractionated softwood kraft lignin and paper grade kraft pulp. Short oxidative stabilisation (<2 h) of thin PFs ultimately provided CFs with tensile modulus and strength of 76 GPa and 1070 MPa, respectively. Considering the high yield (39 wt%), short stabilisation time and promising mechanical properties, the concept of preparing CF from lignin:cellulose blends is a very promising route.

  • 2.
    Bengtsson, Andreas
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Bengtsson, Jenny
    Sedin, Maria
    Sjöholm, Elisabeth
    Carbon fibres from lignin-cellulose precursors: Effect of stabilisation conditionsManuscript (preprint) (Other academic)
  • 3.
    Berglund, Jennie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Wallenberg Wood Science Center.
    Wood Hemicelluloses - Fundamental Insights on Biological and Technical Properties2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hemicelluloses are a group of heterogeneous polysaccharides representing around 30 % of wood where the dominating types are xylans, glucomannans and xyloglucans. Hemicelluloses complex molecular structure makes it difficult to understand the relationship between structure and properties entirely, and their biological role is not yet fully verified. Additionally, hemicelluloses are sensitive to chemical processing and are not utilized to their full potentials for production of value-added products such as materials, additives to food and pharmaceutical products, etc. Increased knowledge regarding their functions is important for the development of both processes and products. The aim with this work has therefore been to increase the fundamental understanding about how the structure and properties of wood hemicelluloses are correlated, and properties such as flexibility, interaction with cellulose, solubility, resistance to chemical-, thermal-, and enzymatic degradation have been explored.

    Molecular dynamics (MD) simulations were used to, in detail, study the structures found in wood hemicelluloses. The flexibility was evaluated by comparing the impact of backbone sugars on the conformational space and also the impact of side groups was considered. Based on the conformational space of backbone glycosidic linkages the flexibility order of hemicelluloses in an aqueous environment was determined to be: xylan > glucomannan > xyloglucan. Additionally, the impact of xylan structure on cellulose interaction was evaluated by MD methods.

    Hemicelluloses were extracted from birch and spruce, and were used to fabricate different composite hydrogels with bacterial cellulose. These materials were studied with regards to mechanical properties, and it was shown that galactoglucomannans mainly contributed to an increased modulus in compression, whereas the most significant effect from xylan was increased strain under uniaxial tensile testing. Besides, other polysaccharides of similar structure as galactoglucomannans were modified and used as pure, well defined, models. Acetyl groups are naturally occurring decorations of wood hemicelluloses and can also be chemically introduced. Here, mannans with different degrees of acetylation were prepared and the influence of structure on solubility in water and the organic solvent DMSO were evaluated. Furthermore, the structure and water solubility influenced the interaction with cellulose. Acetylation also showed to increase the thermal and biological stability of mannans.

    With chemical pulping processes in mind, the degradability of spruce galactoglucomannans in alkaline solution were studied with regards to the structure, and the content of more or less stable structural regions were proposed.

    The full text will be freely available from 2019-12-31 20:00
  • 4.
    Chen, Chao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Petterson, Torbjörn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Illergård, Josefin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Influence of Cellulose Charge on Bacteria Adhesion and Viability to PVAm/CNF/PVAm-Modified Cellulose Model Surfaces2019In: Article in journal (Refereed)
    Abstract [en]

    A contact-active antibacterial approach based on the physical adsorption of a cationic polyelectrolyte onto the surface of a cellulose material is today regarded as an environment-friendly way of creating antibacterial surfaces and materials. In this approach, the electrostatic charge of the treated surfaces is considered to be an important factor for the level of bacteria adsorption and deactivation/killing of the bacteria. In order to clarify the influence of surface charge density of the cellulose on bacteria adsorption as well as on their viability, bacteria were adsorbed onto cellulose model surfaces, which were modified by physically adsorbed cationic polyelectrolytes to create surfaces with different positive charge densities. The surface charge was altered by the layer-by-layer (LbL) assembly of cationic polyvinylamine (PVAm)/anionic cellulose nanofibril/PVAm onto the initially differently charged cellulose model surfaces. After exposing the LbL-treated surfaces to Escherichia coli in aqueous media, a positive correlation was found between the adsorption of bacteria as well as the ratio of nonviable/viable bacteria and the surface charge of the LbL-modified cellulose. By careful colloidal probe atomic force microscopy measurements, it was estimated, due to the difference in surface charges, that interaction forces at least 50 nN between the treated surfaces and a bacterium could be achieved for the surfaces with the highest surface charge, and it is suggested that these considerable interaction forces are sufficient to disrupt the bacterial cell wall and hence kill the bacteria.

  • 5.
    de Carvalho, Danila Morais
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, Stockholm, Sweden.;Univ Fed Vicosa, Vicosa, MG, Brazil..
    Martinez-Abad, Antonio
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, Stockholm, Sweden..
    Colodette, Jorge Luiz
    Univ Fed Vicosa, Vicosa, MG, Brazil..
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, Stockholm, Sweden..
    Vilaplana, Francisco
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, Stockholm, Sweden..
    Sevastyanova, Olena
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Fibre Wood Tech Wood Chem Pulp Tech, Stockholm, Sweden..
    Chemical and structural characterization of xylans from sugarcane bagasse and sugarcane straw2016In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 251Article in journal (Other academic)
  • 6.
    de Carvalho, Danila Morais
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Impact of the chemical composition of cellulosic materials on the nanofibrillation process and nanopaper properties2019In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 127, p. 203-211Article in journal (Refereed)
    Abstract [en]

    This paper investigated the impact of the amounts of lignin and hemicelluloses on cellulose nanofibers (CNFs). Birch and spruce wood were used to prepare holocellulose and cellulose samples by classical methods. To better assess the effect of the chemical composition on the CNF performance and simplify the process for CNF preparation, no surface derivatization method was applied for CNF preparation. Increased amounts of hemicelluloses, especially mannans, improved the defibration process, the stability of the CNFs and the mechanical properties, whereas the residual lignin content had no significant effect on these factors. On the other hand, high lignin content turned spruce nanopapers yellowish and, together with hemicelluloses, reduced the strain-at-break values. Finally, when no surface derivatization was applied to holocellulose and cellulose samples before defibration, the controlled preservation of residual lignin and hemicelluloses on the CNFs indicate to be crucial for the process. This simplified method of CNF preparation presents great potential for forest-based industries as a way to use forestry waste (e.g., branches, stumps, and sawdust) to produce CNFs and, consequently, diversify the product range and reach new markets.

  • 7.
    Ek, Monica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Engström, Ann-Charlott
    Henriksson, Gunnar
    Increase Reactivity of Dissolving Pulps by different pretreatments2006Conference paper (Refereed)
  • 8.
    Ek, Monica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gellerstedt, Göran
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ljungberg Textbook: Pulp and Paper Chemistry and Technology2007Book (Refereed)
  • 9.
    Ek, Monica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ibarra, David
    Köpcke, Viviana
    Larsson, Per Tomas
    Jääskeläinen, Anna-Stiina
    Production of dissolving grade pulps from non-wood paper grade pulps using enzymatic and chemical pre-treatments for the viscose process2010Conference paper (Refereed)
    Abstract [en]

    Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, eg Paper and board but also cellulose-based products which have many important applications in the pharmaceutical, textile, food and paint industries. A raw material with high cellulose content and low content of hemicelluloses, residual lignin, extractives and minerals is required for the prodn. of these products, eg Cotton and dissolving grade pulp are used. However, the high cost prodn. of dissolving grade pulps has aroused the possibility of upgrading paper grade pulps into dissolving pulps by selective removal of hemicelluloses and subsequent activation of the pulps. This study reports the feasibility to produce dissolving grade pulps from different pulps, ie Non-wood paper grade pulps and conventional hardwood kraft pulps, employing enzymic and chem. pretreatments. A monocomponent endoglucanase and a xylanase followed by alk. extn. were tested in order to increase the accessibility and reactivity of the cellulose pulp and decrease the hemicellulose content, resp. An optimization of these treatments in terms of enzyme dosage, incubation time and a possible combination of them was investigated. The treatment effects on reactivity according to Fock's method, viscosity, hemicellulose content and mol. wt. distribution, using size exclusion chromatog.(SEC), were analyzed. The characterization of cellulose structure after the enzymic and chem. treatments was investigated by different techniques.

  • 10.
    Ek, Monica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Illergård, Josefin
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Biointeractive fibres: A sustainable way of fighting bacteria by using antibacterial cellulosic fibres2010Conference paper (Refereed)
    Abstract [en]

    Bacterial growth is a risk of infection. Antibiotics did long time seem to be a soln. to the problem, but now the consequences are seen, as antibiotic-resistant strains are evolving. The substances are also eventually released into the environment, where they often are harmful to living organisms. Antibacterial surfaces state another option. However, a majority of the now existing surfaces are of leaching type ie assocd. with the same problems as the antibiotics. The non-leaching are a safer option, but until now the fabrication has been a problem with use of eg org. solvents. We present a sustainable way of forming an antibacterial material onto cellulose by using the polyelectrolyte multilayer technique. By step-wise adsorbing oppositely charged polyelectrolytes in an aq. soln. contg. fibers, at room-temp., the surface of the fibers are modified. The result is a non-leaching material with bacteria inhibiting properties. Also the fabrication is quite safe, as polymers have shown lower toxicity to humans than their monomeric counterparts. Cellulose is an excellent substrate for antibacterial surfaces. It is easy to modify with the present technique and is in itself a sustainable materials, with multiple applications. Combined this gives us in total a new, antibacterial material which also opens up for sustainable cellulose-based products.

  • 11.
    Ek, Monica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Westman, Eva-Helena
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Cellulose films and fibres with antibacterial properties2007Conference paper (Refereed)
  • 12.
    Giummarella, Nicola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Gioia, Claudio
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Department of Civil, Chemical, Environmental and Materials Engineering. Universita´ di Bologna.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    A One-Pot Biomimetic Synthesis of Selectively Functionalized Lignins from Monomers: A Green Functionalization Platform2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Lignin is the most abundant renewable source of phenolic compound with great application potential in renewable materials, biofuels and platform chemicals. Current technology for producing cellulose-rich fibers co-produces heterogeneous lignin, which includes an untapped source of monomeric phenolics. One such monomer also happen to be the main monomer in soft wood lignin biosynthesis, namely coniferyl alcohol. Herein, we investigate the potential of coniferyl alcohol as a platform monomer for the biomimetic production of tailored functionalized oligolignols with desirable properties for material synthesis. Accordingly, a bifunctional molecule with at least one carboxyl-ended functionality is included with coniferyl alcohol in biomimetic lignin synthesis to, in one-pot, produce a functionalized lignin. The functionalization mechanism is a nucleophilic addition reaction to quinone methide intermediate of lignin polymerization. The solvent systems applied were pure water or 50% aqueous acetone. Several bi-functional molecules differing in the second functionality were successfully inserted in the lignin demonstrating the platform component of this work. Detailed characterizations were performed by a combination of NMR techniques which include 1H NMR, COSY-90, 31P NMR, 13C NMR, 13C APT, HSQC, HMBC and HSQC TOCSY. Excellent selectivity towards benzylic carbon and high functionalization degree were noted. The structure of lignin was tailored through solvent system choice, with the 50% aqeuous acetone producing a skeletal structure favorable for high functionalization degrees. Finally, material concepts are demonstrated using classical Thiol-ene- and Diels Alder- chemistries to show potential for thermoset- and thermoplastic- concepts, respectively. The functionalization concept presents unprecedentent opportunities for green production of lignin-based recyclable biomaterials.

  • 13.
    Giummarella, Nicola
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Pu, Yunqiao
    Ragauskas, Arthur J
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    A Critical Review on the Analysis of Lignin Carbohydrate Bonds2018In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Replacing fossil-based resources with renewable alternatives is generally acknowledged as a critical component to address several of today's environmental concerns. In this context, lignocellulosic biomass is an attractive, sustainable resource. However, the constitutional biopolymers of interest are locked in the structural complexity of the plant cell walls, which defines their properties and contributes to fractionation recalcitrance. One of the key suspects restricting fractionation of the biopolymers in high yield is the presence of lignin-carbohydrate bonds forming a matrix referred to as Lignin-Carbohydrate Complexes (LCC). Nevertheless, covalent bonds between lignin and carbohydrates, remain one of the most controversial topics in lignocellulose chemistry. This challenge can be attributed to the slow progress made in their research, which also forms the basis for this review. Herein, we will critically discuss the literature with a particular focus on the latest characterization and analytical techniques. Discussions on existing techniques and, importantly the drawbacks with them should be compelling to researchers in the area, especially at this time when crucial issues surrounding the realization of biorefineries need to be addressed.

  • 14.
    Giummarella, Nicola
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Fundamental Aspects of Lignin Carbohydrate Complexes (LCC): Mechanisms, Recalcitrance and Material concepts2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Covalent bonds between lignin and carbohydrates, forming a matrix referred to as lignin carbohydrate complexes (LCC), remain one of the most controversial topics in wood chemistry. A key issue is whether they are formed during chemical and mechanical pretreatments of the compact wood structure or actually present in wood prior to isolation. A fundamental understanding of their origin and reactivity is vital to unravel their role in wood formation and recalcitrance. Recalcitrance, specifically, has affected the successful development of effective and clean fractionation of wood polymers.

    To address the above-mentioned concerns, we have developed a novel mild universal and quantitative fractionation protocol of LCC that, when combined with robust spectroscopic analytical tools, including a variety of NMR techniques, GC MS and SEC, reveals deeper insights into the molecular structure of LCC.

    This method was applied to both hardwood and softwood LCCs and revealed interesting findings on molecular-level regulatory mechanism for lignin carbohydrate (LC) bond formation such as the role of acetylation in hemicelluloses. Moreover, the role of LC bonds on recalcitrance during subcritical water extraction was unveiled.

    Bio-mimicking in vitro lignin polymerization was adopted to investigate whether LC bonds are native or formed during isolation from wood. For the first time, direct evidence lending support that they are formed in wood cells was demonstrated, thus corroborating the mechanisms suggested in the literature.  

    Furthermore, based on the overall LCC study, we suggest a sequence for how LC bonds may form in vitro.

    Finally, of special interest to material science, the unveiled LC bond formation mechanism inspired a green, biomimetic, one-pot synthesis of functionalized lignin starting from monomeric components. Excellent selectivity of functionalization is reported and production of lignin-based recyclable materials, based on the premise of this functionalization philosophy, is discussed.

    The full text will be freely available from 2019-05-15 11:59
  • 15.
    Henschen, Jonatan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Preparation of cellulose nanomaterials via cellulose oxalates2019In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 213, p. 208-216Article in journal (Refereed)
    Abstract [en]

    Nanocellulose prepared from cellulose oxalate has been discussed as an alternative to other methods to prepare cellulose nanofibrils or crystals. The current work describes the use of a bulk reaction between pulp and oxalic acid dihydrate to prepare cellulose oxalate followed by homogenization to produce nanocellulose. The prepared nanocellulose is on average 350 nm long and 3–4 nm wide, with particles of size and shape similar to both cellulose nanofibrils and cellulose nanocrystals. Films prepared from this nanocellulose have a maximum tensile stress of 140–200 MPa, strain at break between 3% and 5%, and oxygen permeability in the range of 0.3–0.5 cm 3 μm m −2 day −1 kPa −1 at 50% relative humidity. The presented results illustrate that cellulose oxalates may be a low-cost method to prepare nanocellulose with properties reminiscent of those of both cellulose nanofibrils and cellulose nanocrystals, which may open up new application areas for cellulose nanomaterials.

  • 16. Hermosilla, Viviana
    et al.
    Ibarra, David
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    On the accessibility and reactivity of different kraft pulps used for cellulose derivatives2007Conference paper (Refereed)
  • 17. Hermosilla, Viviana
    et al.
    Nanko, Hiroushi
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Influence of Mechanical and Enzymatic Treatment on Cellulose Accessibility2007Conference paper (Refereed)
  • 18.
    Huang, Tianxiao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Betulin-modified cellulosic textile fibers with improved water repellency, hydrophobicity and antibacterial properties2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Textiles made from natural sources, such as cotton and flax, have advantages over those made of synthetic fibers in terms of sustainability. Unlike major synthetic fibers that have a negative impact on the environment due to poor biodegradability, cotton cellulose is a renewable material.Cotton cellulose fibers exhibit various attractive characteristics such as softness and inexpensiveness. Cellulosic textiles can be easily wetted, since the structure contains a large amount of hydrophilic hydroxyl groups, and when water repellency is needed, this is a disadvantage. Currently, paraffin waxes or fluorinated silanes are used to achieve hydrophobicity, but this contradicts the concept of green chemistry since these chemicals are not biodegradable. The use of bio-based materials like forest residues or side-streams from forest product industries might be a good alternative, since this not only decreases the pressure on the environment but can also increase the value of these renewable resources.Betulin is a hydrophobic extractive present in the outer bark of birch trees (Betula verrucosa). Nowadays, the birch bark containing betulin generated in the paper industry is disposed of by incineration as a solid fuel to provide energy, but this application is not highly valuable and this motivates us to see whether betulin can be used as a hydrophobe to prepare waterproof cellulosic textiles. Methods of dip-coating, film compression molding and grafting were performed to build “betulin-cellulosic textile system” to render the textile with hydrophobicity and other functions. The textile impregnated in a solution of betulin-based copolymer exhibited a contact angle of 151°, which indicated that superhydrophobicity can be reached. AATCC water spray test results showed that cellulosic textile coated with betulin-based film had a water repellency of 80, which is the third highest class according to the rating standards. Betulin-grafted textiles were also prepared and showed a static water contact angle of 136°, and an antibacterial property with a bacterial removal of 99%.This thesis proposes that betulin can be used as a green alternative in functional material preparation. By developing betulin, a more value-added application rather than incineration can be achieved.

  • 19.
    Huang, Tianxiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Water repellency improvement of cellulosic textile fibers by betulin and a betulin-based copolymer2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 3, p. 2115-2128Article in journal (Refereed)
    Abstract [en]

    Betulin is a naturally abundant and hydrophobic compound in the outer bark of birch and can readily be obtained by solvent extraction. Here, solutions of betulin were used to treat cotton fabrics and improve their water repellency. Cotton fabric impregnated in a solution of betulin in ethanol showed a contact angle for water of approximately 153A degrees and reached a water repellency score of 70 according to a standard water repellency test method. A betulin-terephthaloyl chloride (TPC) copolymer was synthesized. Both betulin and betulin-TPC copolymer were characterized by nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The copolymer was characterized by size exclusion chromatography and differential scanning calorimetry. When impregnated with a solution of betulin-TPC copolymer in tetrahydrofuran, a cotton fabric showed a water contact angle of 151A degrees and also reached a water repellency score of 70. Films based on betulin and betulin-TPC copolymer were prepared and coated onto the surface of the fabrics by compression molding. These coated fabrics showed water contact angles of 123A degrees and 104A degrees respectively and each reached a water repellency score of 80.

  • 20.
    Huang, Tianxiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Chen, Chao
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Li, Dongfang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Hydrophobic and antibacterial textile fibres prepared by covalently attaching betulin to cellulose2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Betulin, a natural compound extractable from the outer bark of birch, can be used to improve the properties of cellulosic textile fibres. Herein, oxidation was performed to prepare carboxyl-functionalized cellulose, which was subsequently covalently attached by betulin through esterification. The surface-modified cellulosic textile fibres showed a substantially improved hydrophobicity, as indicated by a water contact angle of 136°. Moreover, the material showed excellent antibacterial properties, as indicated by over 99% bacterial removal and growth inhibition, in both Gram-positive and Gram-negative bacterial assays. The method of surface-modification of the cellulosic materials adapted in this study is simple and, to the best of our knowledge, has not been carried out before. The results of this study prove that betulin, a side-stream product produced by forest industry, could be used in value-added applications, such as for preparing functional materials. Additionally, this modification route can be envisaged to be applied to other cellulose sources (e.g., microfibrillated cellulose) to achieve the goal of functionalization.

  • 21. Ibarra, David
    et al.
    Kopcke, Viviana
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Influence of a novel laboratory endoglucanase on the reactivity and accessibility of dissolving pulp2008Conference paper (Refereed)
    Abstract [en]

    Cellulose is the most abundant biorenewable material, constitutes an important polymer since it is used as raw material for several products, eg cellulose derivs. which have many important applications in the fiber, paper, membrane, polymer, and paints industries. A raw material with high cellulose content is required for the prodn. of cellulose derivs., eg cotton and dissolving pulp are used. Cellulose forms a network structure of fibrils and fibrilar aggregations. Intermol. hydrogen bonds, dipole interactions, and van der Waals interactions bind the cellulose mols. intensively together. The accessibility and reactivity of the cellulose in wood pulps to solvents and reactive agents is usually limited. In this respect, different types of pre-treatments have been assayed to increase the reactivity of cellulose, among them the use of enzymes such as monocomponent cellulases and cellulase mixt. In this work, was investigated the influence of a novel lab. enzyme, from Paenibacillus sp. Strain BP-23, on a com. dissolving pulp from Eucalyptus globulus, in terms of enzyme dosage and incubation time. Evaluation of these parameters in terms of accessibility and reactivity, according to Fockxs method, were investigated. Structural characterization and mol. wt. distribution were carried out using 13C-CP/MAS NMR (Cross-Polarisation Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonanse) and SEC (Size Exclusion Chromatog.), resp.

  • 22. Ibarra, David
    et al.
    Köpcke, Viviana
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Influence of a monocomponent endoglucanase on different fibre raw materials: Study of accessability and reactivity2008Conference paper (Refereed)
  • 23.
    Illergård, Josefin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    Westman, Eva-Helena
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Making biointeractive fibres: Build-up of antibacterial multilayers studied by SPAR2008Conference paper (Refereed)
  • 24. Kasai, Wakako
    et al.
    Morooka, Toshiro
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Fabrication and characterization of cellulosic material prepared by periodate oxidation from pulp2010Conference paper (Refereed)
    Abstract [en]

    ellulose is the most abundant and sustainable natural resource on the earth, and biosynthesized as the major plant component. Main usage of Cellulose is structural materials such as pulp, paper and wood-based materials although cellulose has been used as the derivs. by chem. modifications. Recently, renewable resources are noted for their pos. aspects from an ecol. point of view. The aim of this research is to create high-value-added products from biomass based products such as pulp in order to develop the functional materials leading to new industrial applications. In this presentation, we try to prep. dialc. cellulose by periodate oxidn. from pulp and fabricate and characterize films from the deriv.

  • 25. Köpcke, Viviana
    et al.
    Ibarra, David
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Study on the feasibility of converting kraft pulps into dissolving pulps: accessibility and reactivity2008Conference paper (Refereed)
    Abstract [en]

    For the prodn. of cellulose derivs. raw material contg. high cellulose and low hemicellulose content is required and today's industrial state of the art is to use dissolving pulps produced by sulphite process or prehydrolisis kraft. This work, in contrast, focuses on the study of two different paper-grade kraft pulps from hardwood-birch and eucalyptus--and the possibility to use it as raw material for the prodn. of cellulose derivs. There have been different studies that focus their investigations mainly on the decrease of the hemicellulose content. The aspects of accessibility and reactivity of cellulose towards solvents and reagents, however, are investigated far less although being key parameters when a homogenous substitution is desired for the prodn. of cellulose derivs. of high quality. In order to accomplish the requirements of a com. dissolving pulp, the kraft pulps were subjected to different enzymic treatments using com. enzymes, xylanase and monocomponent endoglucanase. Reactivity (Fock) was notably improved and the hemicellulose content decreased down to com. typical dissolving pulp values. Further on, the structural characteristics of the pulps will be studied by means of 13C-CP/MAS NMR and size exclusion chromatog.(SEC).

  • 26.
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Manufacturing and Characterization of Cellulose Nanofibers2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The usage of wood has been a dominant driving force during the evolution of the human species. It allowed us to cook food, build tools, put roofs over our head and explore the world. The fibers making up the tree has been the most important way to store and transmit knowledge in the form of paper for centuries. It may not be considered as the most interesting or hi-tech of fields, although, nothing could be further from the truth. One of society's most significant issue is how to live sustainably, which is coincidentally exactly what trees can solve. We can live in tall buildings made from wood, locking up vast amounts of carbon dioxide - we can replace many of the plastics we use today with sustainable alternative from the components making up the tree - we could even make clothes from our trees and stop being reliant on the untenable cotton production - only our imagination is holding us back from what can be made from trees.

    Cellulose is the structural component in trees, the molecule arranges itself in a complex hierarchical structure that forms the wood-cells, or fibers. Breaking down this hierarchical structure down to its smallest structural units leaves us with tiny fibers, no longer than a few micrometers and with a width of merely four nanometers. These are cellulose nanofibers, and this work has aimed to understand how and what it takes to liberate these fine fibers from the larger fiber that they make up. Two main pathways exist to liberate the nanofibers, either chemically by introducing negatively charged groups on the surface of the cellulose, making the fibrils repel each other, or mechanically, simply by intense processing of the fibers. However, these processes are associated with certain flaws in that (i) vast amount of energy is required unless the fibers are pretreated, (ii) disintegration is performed in instruments that do not scale well, (iii) disintegration is carried out at a low concentration of fibers, typically below 5%. Additionally, what comes out of a process is difficult to characterize in terms of quality due to an inherent inhomogeneity and the small size of the nanofibers.

    These issues in combination with a greater understanding of the processes are the foundation of this thesis.

    Decreased energy consumption and scalability was explored via the steam explosion concept Nanopulp. In order to avoid issues associated with the low concentration, a method was developed for drying cellulose nanofibers to a paste without causing hornification using glycerol. A variety of cellulose nanofibers from different sources were prepared and characterization techniques were compared and expanded upon, including the development of a method for better describing the surface area of cellulose nanofibers. Finally, an environmentally friendly composite was made using cheap and available resources in combination with cellulose nanofibers.

  • 27.
    Moser, Carl
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Backlund, Hanéle
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Xyloglucan for estimating the surface area of cellulose fibers2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 2, p. 194-199Article in journal (Refereed)
    Abstract [en]

    The hemicellulose xyloglucan can be utilized to measure exposed cellulose surfaces for pulp fibers. This was shown by correlating a refining series with the adsorbed amount of xyloglucan, and by swelling cellulose fibers to various degrees by increasing the charge density. The method is specific to cellulose and could be used to quantify refining or to determine hornification.

  • 28.
    Moser, Carl
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH Royal Institute of Technology.
    Backlund, Hanéle
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Louise, Drenth
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Gunnar, Henriksson
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Mikael E., Lindström
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Xyloglucan adsorption for measuring the specific surface area on various never-dried cellulose nanofibers2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 2, p. 186-193Article in journal (Refereed)
    Abstract [en]

    In this paper, we explore xyloglucan adsorption to cellulose nanofibers as a method for the evaluation of their quality (i. e., the degree of disintegration) and the accessible surface area in the wet state and at low ionic strength. This method was shown to be capable of estimating the surface areas of 14 different cellulose nanofiber qualities from both hardwood and softwood with different pretreatments, including enzymatic hydrolysis using a monocomponent endoglucanase, TEMPO-mediated oxidation, and carboxymethylation. The cellulose surface measured using this method showed a correlation with the degree of disintegration expressed as transmittance for different concentrations of xyloglucan.

  • 29.
    Moser, Carl
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Improved dispersibility of once-dried cellulose nanofibers in the presence of glycerol2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669Article in journal (Refereed)
    Abstract [en]

    To investigate the dispersibility of dried cellulose nanofibers (CNFs), various additions (glycerol, octanol, glycol, and sodium perchlorate) were added to CNFs prior to drying. Glycerol was the only species to show any significant effect on re-dispersibility. The sedimentation was slower, and the transmittance of the solution was comparable to that of its undried counterpart. Increasing the amount of glycerol showed a clear trend with regard to dispersibility. The mechanical properties of films were maintained for samples that were dried and redispersed in the presence of glycerol.

  • 30.
    Moser, Carl
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lindström, Mikael E.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Structural aspects on the manufacturing of cellulose nanofibers from wood pulp fibersManuscript (preprint) (Other academic)
  • 31.
    Ottenhall, Anna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Antimicrobial materials from cellulose using environmentally friendly techniques2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The transition to a more biobased society introduces both new opportunities and new challenges as we replace nonrenewable materials with renewable alternatives. One important challenge will be to control microbial growth on materials, both to protect the materials from biological degradation and to prevent the spread of infections and toxins that can cause illness.

    In this thesis, both existing and new types of cellulose-based materials were treated with environmentally friendly alternatives to usual biocides to prevent microbial growth and remove bacteria from water. Two types of antimicrobial systems were studied, and the antimicrobial effects were evaluated for bacteria and fungi using both model organisms and wild-type cultures.

    The first antimicrobial approach employed was a nonleaching and contact-active layer-by-layer adsorption of polyelectrolytes to provide the cellulose fibers with a cationic surface charge, which attracts and captures bacteria onto the fiber surface. The study showed that paper filters with pores much larger than bacteria could remove more than 99.9 % of E. coli from water when used in filtration mode. The polyelectrolyte-modified materials showed a good antibacterial effect but did not prevent fungal growth.

    The second approach was to utilize biobased compounds with antimicrobial properties, which were applied to cellulose fiber foam materials. Chitosan and extractives from birch bark were selected as biobased options for antimicrobial agents. Two types of cellulose fiber foam materials were developed and evaluated for their antimicrobial properties.

    This thesis shows the importance of understanding both the application and the targeted microorganism when selecting an environmentally friendly antimicrobial system for treating biobased materials. It highlights that a good understanding of both material science and microbiology is important when designing new antimicrobial materials.

  • 32.
    Ottenhall, Anna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Henschen, Jonatan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Illergård, Josefin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Cellulose-based water purification using paper filters modified with polyelectrolyte multilayers to remove bacteria from water through electrostatic interactions2018In: Environmental Science: Water Research & Technology, ISSN 20531400Article in journal (Refereed)
    Abstract [en]

    Filtration is a common way to obtain pure drinking water by removing particles and microorganisms based on size exclusion. Cellulose-based filters are affordable and biobased option for the removal of particles but bacteria are usually too small to be removed by size exclusion alone. In this article, the surfaces of cellulose fibres in two types of commercial paper filters have been given a positive net charge to trap bacteria through electrostatic interactions without releasing any biocides. The fibres were modified with the cationic polyelectrolyte polyvinylamine polymer in single layers (1 L) or in multilayers together with the anionic polyelectrolyte polyacrylic acid (3 L or 5 L) using a water-based process at room temperature. Filtration tests show that all filters, using both types of filter papers and a number of layers, can physically remove more than 99.9% of E. coli from water and that the 3 L modified filters can remove more than 97% of cultivatable bacteria from natural water samples. The bacterial reduction increased with increasing number of filter sheets used for the filtration and the majority of the bacteria were trapped in the top sheets of the filter. The results show the potential for creating water purification filters from bio-based everyday consumable products with a simple modification process. The filters could be used in the future for point-of-use water purification that may be able to save lives without releasing bactericides.

  • 33.
    Ottenhall, Anna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Illergård, Josefin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Water Purification Using Functionalized Cellulosic Fibers with Nonleaching Bacteria Adsorbing Properties2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, p. 7616-7623Article in journal (Refereed)
    Abstract [en]

    Portable purification systems are easy ways to obtain clean drinking water when there is no large-scale water treatment available. In this study, the potential to purify water using bacteria adsorbing cellulosic fibers, functionalized with polyelectrolytes according to the layer-by-layer method, is investigated. The adsorbed polyelectrolytes create a positive charge on the fiber surface that physically attracts and bonds with bacteria. Three types of cellulosic materials have been modified and tested for the bacterial removal capacity in water. The time, material-water ratio and bacterial concentration dependence, as well as the bacterial removal capacity in water from natural sources, have been evaluated. Freely dispersed bacteria adsorbing cellulosic fibers can remove greater than 99.9% of Escherichia coli from nonturbid water, with the most notable reduction occurring within the first hour. A filtering approach using modified cellulosic fibers is desirable for purification of natural water. An initial filtration test showed that polyelectrolyte multilayer modified cellulosic fibers can remove greater than 99% of bacteria from natural water. The bacteria adsorbing cellulosic fibers do not leach any biocides, and it is an environmentally sustainable and cheap option for disposable water purification devices.

  • 34.
    Ottenhall, Anna
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Seppänen, Tiinamari
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Water-stable cellulose fiber foam with antimicrobial properties for bio based low-density materials2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 5, p. 2599-2613Article in journal (Refereed)
    Abstract [en]

    New bio-based packaging materials are highly interesting for replacing conventional fossil based products for a more sustainable society. Water-stable cellulose fiber foams have been produced in a simple one-batch foam-forming process with drying under ambient conditions. The cellulose fiber foams have a low density (33–66 kg/m3) and can inhibit microbial growth; two highly valuable features for insulating packaging materials, especially in combination with stability in water. Cationic chitosan and/or polyvinylamine have been added during the foam-forming process to give the foams water-stability and antimicrobial properties. The structural and mechanical properties of the cellulose fiber foams have been studied and the antimicrobial properties have been evaluated with respect to both Escherichia coli, a common model bacteria and Aspergillus brasiliensis, a sporulating mold. The cellulose foams containing chitosan had both good water-stability and good antibacterial and antifungal properties, while the foams containing PVAm did disintegrate in water and did not inhibit fungal growth when nutrients were added to the foam, showing that it is possible to produce a bio-based foam material with the desired characters. This can be an interesting low-density packaging material for protection from both mechanical and microbial damage without using any toxic compounds.

  • 35.
    Sevastyanova, Olena
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Evaluation of Ionic Liquids as direct solvents for the manufacturing of novel products from cellulose2010Conference paper (Refereed)
  • 36. Sjödahl, Ragnar
    et al.
    Keyoumu, Ayiguli
    Axelsson, Patrik
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Dissolved wood components in the kraft pulping liquor: Effect on the rate of delignification and bleachability2003Conference paper (Refereed)
  • 37.
    Tagami, Ayumu
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Nippon Paper Industries Co., Ltd. .
    Towards molecular weight-dependent uses of kraft lignin2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is growing demand for a more efficient use of polymers that originate from renewable feedstocks due to the depleting supply of fossil fuels, based on economic and environmental reasons. As a result, lignin has attracted renewed interest as a resource for various bioproducts. Lignin is a natural biopolymer with a high carbon content and is composed of aromatic moieties, with a high level of polar functionalities. This makes it a unique precursor for certain high-value applications, such as in biofuels, bioplastics, composite materials, carbon fibers and activated carbons and as a source of phenolic monomers and fine chemicals.

    Industrial lignins are formed as byproducts of pulping processes (such as kraft, sulfite or alkaline pulping) or result from the biorefining process, where carbohydrates are used for sugar production. Lignin’s intrinsic structure is significantly modified during the processing of lignocellulose, resulting in the formation of more diverse, condensed and less reactive raw materials. Since molecular mass and polydispersity are the most important parameters affecting the chemical reactivity and thermal properties of lignin, additional process steps to improve the quality of crude technical lignins, including kraft lignin, are needed. Solvent extraction is a potentially useful technique for further improving the polydispersity of technical lignins.

    This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating value, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The purpose was to understand the correlation between certain structural features in the lignin fractions and their properties to select the appropriate solvent combinations for specific applications of lignin raw materials.

    Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations were used to separate both spruce and eucalyptus kraft lignins into fractions with lower polydispersities. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material were characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes during the analysis, while the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye.

    Additionally, lignin fractions with different molecular weights (and therefore various chemical structures) that were isolated from both softwood and hardwood kraft lignins were incorporated into a tunicate cellulose nanofiber (CNF)-starch mixture to prepare 100% bio-based composite films. The aim was to investigate the correlation between lignin diversity and film performance. The transmittance, density and thermal properties of the films were investigated, as were their mechanical properties, including the tensile stress and Young’s modulus.

    This part of the study addressed the importance of lignin diversity on composite film performance, which could be helpful for tailoring lignin applications in bio-based composite materials based on the material’s specific requirements.

  • 38.
    Tagami, Ayumu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Nippon paper Industries Co., Ltd..
    Gioia, Claudio
    University of Bologna.
    Lauberts, Maris
    Latvian State Institute of Wood Chemistry.
    Budnyak, Tetyana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Moriana, Rosana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. HIS-University of Skövde.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Solvent fractionation of softwood and hardwood kraft lignins for more efficient uses: compositional, structural, thermal, antioxidant and sorption propertiesManuscript (preprint) (Other academic)
    Abstract [en]

    This work summarizes the impact of solvent fractionation on the chemical structure, antioxidant activity, heating values, and thermal and sorption properties of industrial hardwood and softwood kraft lignins. The aim was to develop a simple approach for the obtaining of lignin fractions with a tailored properties for the certain material applications.  Four common industrial solvents, namely, ethyl acetate, ethanol, methanol and acetone, in various combinations efficiently separated both spruce and eucalyptus kraft lignins into fractions with low polydispersities. The ethanol fraction of spruce and the ethyl acetate fraction of eucalyptus afforded the highest yields. Gel-permeation chromatography analysis was used to evaluate the efficiency of the chosen solvent combination for lignin fractionation. The composition and structure of the lignin material was characterized by elemental analysis, analytical pyrolysis (Py-GC/MS/FID) and 31P NMR spectroscopy. The thermal properties of the lignin samples were studied by thermogravimetric analysis. Proximate analysis data (ash, volatile components, organic matter and fixed carbon) were obtained through the direct measurement of weight changes in each experimental curve, and the high heating values (in MJ/kg) were calculated according to equations suggested in the literature. The sorption properties of fractionated kraft lignins were studied with respect to methylene blue dye. The clear correlation between certain structural features in the lignin fractions and the properties of the lignin provides useful information for selecting the appropriate solvent combinations for specific applications of lignin raw materials, including as antioxidants, biofuels or sorbents in water treatment processes.

    The full text will be freely available from 2019-09-14 15:00
  • 39.
    Tagami, Ayumu
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Nippon paper Industries Co., Ltd. .
    Zhao, Yadong
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Dobele, Galina
    Latvian State Institute of Wood Chemistry.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology. KTH, Superseded Departments (pre-2005), Pulp and Paper Technology.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Lignin-modified tunicate cellulose nanofiber (CNF)-starch composites: impact of lignin diversity on film performanceManuscript (preprint) (Other academic)
    Abstract [en]

    Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF) - starch mixture to prepare 100% bio-based composite films. The aim was to investigate the correlation between lignin diversity and film performance. It was confirmed that lignin’s distribution in the films was dependent on the solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The -OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to the thermal stability decrease and the Young's modulus increase of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic -OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol contents, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the positive relationship between the antioxidant ability of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin’s applications in bio-based materials based on their specific characteristics.

    The full text will be freely available from 2019-09-14 15:00
  • 40. Villaverde, Juan Jos
    et al.
    Li, Jiebing
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ligero, Pablo
    Vega, Alberto de
    Structural characterization of Acetosolve lignin from Miscanthus sinensis2008Conference paper (Refereed)
  • 41.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH Royal Inst Technol, Stockholm, Sweden..
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. KTH Royal Inst Technol, Stockholm, Sweden.;Valmet AB, Sundsvall, Sweden..
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH Royal Inst Technol, Stockholm, Sweden..
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH Royal Inst Technol, Stockholm, Sweden..
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH Royal Inst Technol, Stockholm, Sweden..
    Film formation and performance of different nanocelluloses obtained from different cellulose sources after different preparation processes2017In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Article in journal (Other academic)
  • 42.
    Zheng, Chao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Dongfang
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.
    Bio-based fire retardant and its application in cellulose-based thermal insulation materials2018Conference paper (Refereed)
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