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  • 1.
    Agustin, Melissa B.
    et al.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; VTT Technical Research Centre of Finland Ltd., P.O. Box 1000, FI-02044, Espoo, Finland.
    Nematollahi, Neda
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland.
    Bhattarai, Mamata
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, 00076, Aalto, Finland.
    Oliaei, Erfan
    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, Biocomposites.
    Lehtonen, Mari
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland.
    Rojas, Orlando J.
    Department of Bioproducts and Biosystems, Aalto University, P.O. Box 16300, 00076, Aalto, Finland; Bioproducts Institute, Department of Chemical and Biological Engineering, Department of Chemistry and Department of Wood Science, University of British Columbia, 2360, East Mall, Vancouver, BC, V6T 1Z3, Canada.
    Mikkonen, Kirsi S.
    Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki, P.O. Box 66, FI-00014, Helsinki, Finland; Helsinki Institute of Sustainability Science, University of Helsinki, P.O. Box 65, FI-00014, Helsinki, Finland.
    Lignin nanoparticles as co-stabilizers and modifiers of nanocellulose-based Pickering emulsions and foams2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 30, no 14, p. 8955-8971Article in journal (Refereed)
    Abstract [en]

    Nanocellulose is very hydrophilic, preventing interactions with the oil phase in Pickering emulsions. This limitation is herein addressed by incorporating lignin nanoparticles (LNPs) as co-stabilizers of nanocellulose-based Pickering emulsions. LNP addition decreases the oil droplet size and slows creaming at pH 5 and 8 and with increasing LNP content. Emulsification at pH 3 and LNP cationization lead to droplet flocculation and rapid creaming. LNP application for emulsification, prior or simultaneously with nanocellulose, favors stability given the improved interactions with the oil phase. The Pickering emulsions can be freeze–dried, enabling the recovery of a solid macroporous foam that can act as adsorbent for pharmaceutical pollutants. Overall, the properties of nanocellulose-based Pickering emulsions and foams can be tailored by LNP addition. This strategy offers a unique, green approach to stabilize biphasic systems using bio-based nanomaterials without tedious and costly modification procedures.

  • 2.
    Amorim, Lúcia F.A.
    et al.
    FibEnTech Research Unit, Faculty of Engineering, University of Beira Interior, Covilhã, Portugal.
    Li, Lengwan
    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, Biocomposites.
    Gomes, Ana P.
    FibEnTech Research Unit, Faculty of Engineering, University of Beira Interior, Covilhã, Portugal.
    Fangueiro, Raul
    Centre for Textile Science and Technology (2C2T), University of Minho, Guimarães, Portugal.
    Gouveia, Isabel C.
    FibEnTech Research Unit, Faculty of Engineering, University of Beira Interior, Covilhã, Portugal.
    Sustainable bacterial cellulose production by low cost feedstock: evaluation of apple and tea by-products as alternative sources of nutrients2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 30, no 9, p. 5589-5606Article in journal (Refereed)
    Abstract [en]

    The high applicability of Bacterial Cellulose (BC) is often challenging due to its high production costs, which ultimately prevents its widespread use. Therefore, the present study aimed to investigate BC production using alternative feedstock to replace high-cost synthetic carbon and nitrogen sources and to evaluate the physical and structural properties of the produced BC membranes. BC was produced through a microbial consortium from kombucha, and the formulated alternative media sustained promising BC production, especially the association of apple wastes (at 10% (W/V)) with tea mixture, with a yield similar to BC produced on Hestrin–Schramm (HS) control media. Moreover, the BC samples produced in this alternative media also exhibited comparable properties to BC from HS media, with similar water-holding capacity and retention ability, thermal stability, mechanical behavior, and a crystallinity index of 87.61% and 88.08%, respectively. Thus, our findings substantiated that expensive substrates, such as glucose, peptone, and yeast extract, could be successfully replaced by apple wastes, black and green tea, for BC production while maintaining its remarkable physical and structural properties. Furthermore, besides the low-cost advantage, the bioconversion of apple waste also reduces the environmental burden caused by its disposal in landfills.

  • 3. Andreasson, B.
    et al.
    Forsstrom, J.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Determination of fibre pore structure: influence of salt, pH and conventional wet strength resins2005In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 12, no 3, p. 253-265Article in journal (Refereed)
    Abstract [en]

    It has been shown, in the present investigation, that the two methods used to investigate the pore size distribution of unbleached chemical pulps, i.e. inverse size exclusion chromatography (ISEC) and nuclear magnetic resonance (NMR), give different average pore radius for the pores inside the fibre wall. This is due to the way in which these experiments are performed and the sensitivity of the methods to different types of pores in the cell wall. It was also shown that the two methods gave different results when changing the pH and the ionic strength of the pulp suspension. The pore radius, as detected with ISEC, decreased with both increasing ionic strength and decreasing pH, indicating a loose structure of the exterior of the fibrillar network. However, the pore radius as detected with NMR, was virtually unaffected when increasing the ionic strength, indicating a very rigid structure of the interior of the fibre wall. Decreasing pH though, lead to a decrease in pore radius indicating that upon protonation of the carboxylic groups in the fibre wall, the electrostatic repulsion is diminished and the average pore radius decreases. The NMR technique was also used to study wet strength aid penetration into the fibre wall. It was shown that wet strength aids with a small molecular weight, penetrated the fibre wall, as detected by a decrease in pore radius. It was also shown that addition of different wet strength aids increased the tensile index of the sheet and decreased the fibre strength, measured as zero span-strength of the sheets.

  • 4. Andreasson, B.
    et al.
    Forsstrom, J.
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    The porous structure of pulp fibres with different yields and its influence on paper strength2003In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 10, no 2, p. 111-123Article in journal (Refereed)
    Abstract [en]

    The porous structure of the interior of papermaking fibres is a well-known important property of the fibres. Changes of this structure will influence tensile and burst strength of paper formed from the fibres and a change in pore size of the pores within the fibre wall is also important for the ability of molecules to diffuse in and out of the fibre wall. Relevant examples of this latter effect are the removal of lignin during cooking and the addition of performance chemicals during papermaking. In this paper, pore sizes and the pore size distribution of unbleached softwood fibres have been studied. A well-characterised fibre material consisting of laboratory cooked spruce and pine pulp of various lignin contents was used. Pore size and pore size distribution were measured by studies of the relaxation behaviour of H-2 in fibres saturated with (H2O)-H-2. Beside this the total and surface charge of the fibres were also measured together with strength properties of papers from unbeaten fibres. For both pulps, there is a maximum in pore radius at a yield around 46%. Calculations of fibre wall volume from water retention values and yield levels show that there is a discontinuity in pore radius as a function of the fibre wall volume around a yield of 51%. It is suggested that this discontinuity is caused by the breakdown of the hemicellulose/ lignin matrix within the fibre wall at this yield level. The strength of the papers formed from the fibres shows a correlation with the surface charge of the fibres. Based on the change in surface charge with yield and the change in total charge with yield, this correlation is suggested to be due to an opening up of the external part of the fibre wall. This stresses the importance of the chemical composition and physical structure of the outer layer of the fibre wall.

  • 5.
    Aulin, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gallstedt, Mikael
    Lindström, Tom
    Oxygen and oil barrier properties of microfibrillated cellulose films and coatings2010In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 3, p. 559-574Article in journal (Refereed)
    Abstract [en]

    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.

  • 6.
    Bergenstrahle-Wohlert, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    d'Ortoli, Thibault Angles
    Sjoberg, Nils A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Widmalm, Goran
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    On the anomalous temperature dependence of cellulose aqueous solubility2016In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2375-2387Article in journal (Refereed)
  • 7.
    Bergenstråhle-Wohlert, Malin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Brady, John W.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Westlund, Per-Olof
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Concentration enrichment of urea at cellulose surfaces: results from molecular dynamics simulations and NMR spectroscopy2012In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    A combined solid-state NMR and Molecular Dynamics simulation study of cellulose in urea aqueous solution and in pure water was conducted. It was found that the local concentration of urea is significantly enhanced at the cellulose/solution interface. There, urea molecules interact directly with the cellulose through both hydrogen bonds and favorable dispersion interactions, which seem to be the driving force behind the aggregation. The CP/MAS (13)C spectra was affected by the presence of urea at high concentrations, most notably the signal at 83.4 ppm, which has previously been assigned to C4 atoms in cellulose chains located at surfaces parallel to the (110) crystallographic plane of the cellulose I beta crystal. Also dynamic properties of the cellulose surfaces, probed by spin-lattice relaxation time (13)CT (1) measurements of C4 atoms, are affected by the addition of urea. Molecular Dynamics simulations reproduce the trends of the T (1) measurements and lends new support to the assignment of signals from individual surfaces. That urea in solution is interacting directly with cellulose may have implications on our understanding of the mechanisms behind cellulose dissolution in alkali/urea aqueous solutions.

  • 8.
    Berglund, Jennie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Azhar, Shoaib
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Vilaplana, Francisco
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. 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.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    The structure of galactoglucomannan impacts the degradation under alkaline conditions2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882XArticle in journal (Refereed)
    Abstract [en]

    Galactoglucomannan (GGM) from sprucewas studied with respect to the degradation behavior inalkaline solution. Three reference systems includinggalactomannan from locust bean gum, glucomannanfrom konjac and the linear water-soluble carboxymethylcellulose were studied with focus onmolecular weight, sugar composition, degradationproducts, as well as formed oligomers, to identifyrelative structural changes in GGM. Initially allmannan polysaccharides showed a fast decrease inthe molecular weight, which became stable in the laterstage. The degradation of the mannan polysaccharidescould be described by a function corresponding to thesum of two first order reactions; one slow that wasascribed to peeling, and one fast that was connectedwith hydrolysis. The galactose side group wasstable under conditions used in this study (150 min,90 C, 0.5 M NaOH). This could suggest that, apartfrom the covalent connection to C6 in mannose, thegalactose substitutions also interact non-covalentlywith the backbone to stabilize the structure againstdegradation. Additionally, the combination of differentbackbone sugars seems to affect the stability of thepolysaccharides. For carboxymethyl cellulose thedegradation was linear over time which furthersuggests that the structure and sugar composition playan important role for the alkaline degradation. Moleculardynamics simulations gave details about theconformational behavior of GGM oligomers in watersolution, as well as interaction between the oligomersand hydroxide ions.

  • 9.
    Brandberg, August
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Compression failure in dense non-woven fiber networks2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 10, p. 6065-6082Article in journal (Refereed)
    Abstract [en]

    Investigating the compression properties of randomly ordered fiber networks experimentally is difficult which has resulted in ongoing disputes as to the mechanisms controlling the compression strength in such materials. In this work, we investigated compression properties of randomly oriented fiber networks with a special emphasis on cellulose products such as paperboard. We numerically reconstructed the conditions of the short span compression test widely used to quantify the compression strength of paperboard. We found that the phenomenological failure mode of such networks is elasto-plastic buckling. The x-shaped failure mode observed in physical experiments appears when test specimen restraints are included in the model. The most significant improvements to sheet strength can be obtained by improving the elastic properties while the strain to failure is increased most by an improvement of the plastic yield and hardening properties of individual fibers. Bond breaks were confirmed to have a smaller influence on the overall response. Fiber level microscopic buckling was investigated in depth, providing quantitative estimates of the fraction of mass likely to buckle at the microscopic level. The analysis indicated that only a low to moderate number of load carrying fibers can be expected to buckle. The inherent strength reserve in non-ordered fiber networks was investigated by introducing hinge mechanisms throughout the network, and the effect was shown to be small for a small to moderate number of hinges.

  • 10. Brännvall, Elisabet
    et al.
    Aulin, Christian
    CNFs from softwood pulp fibers containing hemicellulose and lignin2022In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 29, no 9, p. 4961-4976Article in journal (Refereed)
  • 11.
    Butchosa, Nuria
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Leijon, Felicia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Bulone, Vincent
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience.
    Zhou, Qi
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Stronger cellulose microfibril network structure through the expression of cellulose-binding modules in plant primary cell walls2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 5, p. 3083-3094Article in journal (Refereed)
    Abstract [en]

    Cellulose-binding modules (CBMs) are non-catalytic domains typically occurring in glycoside hydrolases. Their specific interaction with diverse polysaccharides assists hydrolysis by the catalytic subunits. In this work, we have exploited the interactions between a CBM from family 3 (CBM3) and cell wall polysaccharides to alter the structure and mechanical properties of cellulose microfibrils from BY-2 tobacco cell suspension cultures. A CBM3 from Clostridium thermocellum was overexpressed in the cells using Agrobacterium-mediated transformation. Water suspensions of cellulose microfibrils were prepared by the removal of the non-cellulosic components of the primary cell walls, followed by mild disintegration using sonication. The morphology of the microfibrils was characterized by transmission electron microscopy and atomic force microscopy. These cellulose microfibrils were further hydrolyzed with 64wt% sulfuric acid to produce cellulose nanocrystals (CNCs). The average length of CNCs prepared from the CBM3-transformed cells was 201nm, higher than that from the wild-type cells (122nm). In addition, the mechanical properties and deformation mechanism of nanopapers prepared from suspensions of cellulose microfibrils were investigated. The nanopapers obtained from the CBM3-transformed cells exhibited enhanced tensile strength and work of fracture, 40% and 128% higher than those prepared from wild-type tobacco cells, respectively. [GRAPHICS] .

  • 12.
    Butchosa, Núria
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Water redispersible cellulose nanofibrils adsorbed with carboxymethyl cellulose2014In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 6, p. 4349-4358Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) are difficult to redisperse in water after they have been completely dried due to the irreversible agglomeration of cellulose during drying. Here, we have developed a simple process to prepare water-redispersible dried CNFs by the adsorption of small amounts of carboxymethyl cellulose (CMC) and oven drying. The adsorption of CMC onto CNFs in water suspensions at 22 and 121 °C was studied, and the adsorbed amount of CMC was measured via conductimetric titration. The water-redispersibility of dried CNFs adsorbed with different amounts of CMC was characterized by sedimentation test. Above a critical threshold of CMC adsorption, i.e. 2.3 wt%, the oven dried CNF–CMC sample was fully redispersible in water. The morphology, rheological, and mechanical properties of water-redispersed CNF–CMC samples were investigated by field emission scanning electron microscopy, viscosity measurement, and tensile test, respectively. The water-redispersed CNFs preserved the original properties of never dried CNFs. This new method will facilitate the production, transportation and storage, and large-scale industrial applications of CNFs.

  • 13.
    Carlsson, Linn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ingverud, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Blomberg, Hanna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Surface characteristics of cellulose nanoparticles grafted by surface-initiated ring-opening polymerization of epsilon-caprolactone2015In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1063-1074Article in journal (Refereed)
    Abstract [en]

    In this study, surface-initiated ring-opening polymerization has been employed for the grafting of epsilon-caprolactone from cellulose nanoparticles, made by partial hydrolysis of cellulose cotton linters. A sacrificial initiator was employed during the grafting reactions, to form free polymer in parallel to the grafting reaction. The degree of polymerization of the polymer grafts, and of the free polymer, was varied by varying the reaction time. The aim of this study was to estimate the cellulose nanoparticle degree of surface substitution at different reaction times. This was accomplished by combining measurement results from spectroscopy and chromatography. The prepared cellulose nanoparticles were shown to have 3.1 (+/- 0.3) % of the total anhydroglucose unit content present at the cellulose nanoparticle surfaces. This effectively limits the amount of cellulose that can be targeted by the SI-ROP reactions. For a certain SI-ROP reaction time, it was assumed that the resulting degree of polymerization (DP) of the grafts and the DP of the free polymer were equal. Based on this assumption it was shown that the cellulose nanoparticle surface degree of substitution remained approximately constant (3-7 %) and seemingly independent of SI-ROP reaction time. We believe this work to be an important step towards a deeper understanding of the processes and properties controlling SI-ROP reactions occurring at cellulose surfaces.

  • 14.
    Cervin, Nicholas Tchang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Aulin, Christian
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids2012In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 2, p. 401-410Article in journal (Refereed)
    Abstract [en]

    A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (> 99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the aerogel and the aerogel can then be reused for a second absorption cycle.

  • 15. Charani, P. Rezayati
    et al.
    Dehghani-Firouzabadi, M.
    Afra, E.
    Blademo, A.
    Naderi, A.
    Lindström, Tom
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Production of microfibrillated cellulose from unbleached kraft pulp of Kenaf and Scotch Pine and its effect on the properties of hardwood kraft: microfibrillated cellulose paper2013In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 5, p. 2559-2567Article in journal (Refereed)
    Abstract [en]

    This work investigated the effect of using Kenaf bast fibre kraft pulps compared to Scotch Pine kraft pulps for producing microfibrillated cellulose (MFC) and its employment for improving mechanical and physical properties of handsheets made from unbleached kraft hardwood pulp. It was shown that MFC based on Kenaf fibres can be produced at higher consistencies [> 5 % (w/w)] compared to when Scotch Pine is employed [a parts per thousand 2 % (w/w)] as raw material. The possibility of using a higher consistency when processing Kenaf is beneficial for the processing in microfluidizers. The rheological properties of the products were shown to be consistent with what is known for MFC-based systems. The studies indicate that the mechanical properties of handsheets from unbleached kraft hardwood pulp can be improved by replacing part of the unbleached kraft hardwood pulp fibres with either unbleached kraft Kenaf pulp or unbleached Scotch Pine kraft pulp. However, the same levels of improvements were obtained when using only a small amount [a parts per thousand 6 % (w/w)] of MFC based on Kenaf or Scotch Pine, when introduced into the system either as a dry strength additive or by coating pre-made handsheets. Finally, it was shown that the incorporation of MFC in handsheets decreases the air-permeability; this effect became amplified when the MFC was applied as a coating onto the handsheets.

  • 16. Chen, P.
    et al.
    Nishiyama, Y.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Quantifying the influence of dispersion interactions on the elastic properties of crystalline cellulose2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 17, p. 10777-10786Article in journal (Refereed)
    Abstract [en]

    Dispersion and electrostatic interactions both contribute significantly to the tight assembly of macromolecular chains within crystalline polysaccharides. Using dispersion-corrected density functional theory (DFT) calculation, we estimated the elastic tensor of the four crystalline cellulose allomorphs whose crystal structures that are hitherto available, namely, cellulose Iα, Iβ, II, IIII. Comparison between calculations with and without dispersion correction allows quantification of the exact contribution of dispersion to stiffness at molecular level.

  • 17. Chen, Pan
    et al.
    Ogawa, Yu
    Nishiyama, Yoshiharu
    Bergenstråhle-Wohlert, Malin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mazeau, Karim
    Alternative hydrogen bond models of cellulose II and IIII based on molecular force-fields and density functional theory2015In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 3, p. 1485-1493Article in journal (Refereed)
    Abstract [en]

    Alternative hydrogen-bond structures were found for cellulose II and IIII based on molecular dynamics simulations using four force fields and energy optimization based on density functional theory. All the modeling results were in support to the new hydrogen-bonding network. The revised structures of cellulose II and IIII differ with the fiber diffraction models mainly in the orientation of two hydroxyl groups, namely, OH2 and OH6 forming hydrogen-bond chains perpendicular to the cellulose molecule. In the alternative structures, the sense of hydrogen bond is inversed but little difference can be seen in hydrogen bond geometries. The preference of these alternative hydrogen bond structures comes from the local stabilization of hydroxyl groups with respect to the beta carbon. On the other hand when simulated fiber diffraction patterns were compared with experimental ones, the current structure of cellulose II with higher energy and the alternative structure of cellulose IIII with lower energy were in better agreement.

  • 18.
    Chen, Pan
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. South China Univ Technol, State Key Lab Pulp & Paper Engn, Guangzhou 510640, Guangdong, Peoples R China.
    Ogawa, Yu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Nishiyama, Yoshiharu
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    Ismail, Ahmed E.
    West Virginia Univ, Dept Chem & Biomed Engn, Morgantown, WV 26505 USA..
    Mazeau, Karim
    Univ Grenoble Alpes, CNRS, CERMAV, BP53, F-38000 Grenoble 9, France..
    I alpha to I beta mechano-conversion and amorphization in native cellulose simulated by crystal bending2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 8, p. 4345-4355Article in journal (Refereed)
    Abstract [en]

    The bending of rod-like native cellulose crystals with degree of polymerization 40 and 160 using molecular dynamics simulations resulted in a deformation-induced local amorphization at the kinking point and allomorphic interconversion between cellulose I alpha and I beta in the unbent segments. The transformation mechanism involves a longitudinal chain slippage of the hydrogen-bonded sheets by the length of one anhydroglucose residue ( 0.5 nm), which alters the chain stacking from the monotonic (I alpha) form to the alternating I beta one or vice versa. This mechanical deformation converts the I alpha form progressively to the I beta form, as has been experimentally observed for ultrasonication of microfibrils. I beta is also able to partially convert to I alpha-like organization but this conversion is only transitory. The qualitative agreement between the behavior of ultrasonicated microfibrils and in silico observed I alpha -> I beta conversion suggests that shear deformation and chain slippage under bending deformation is a general process when cellulose fibrils experience lateral mechanical stress.

  • 19.
    Choong, Ferdinand X.
    et al.
    Swedish Medical Nanoscience Center, Department of Neuroscience Karolinska Institutet, Stockholm, Sweden.
    Lantz, Linda
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Shirani, Hamid
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Schulz, Anette
    Swedish Medical Nanoscience Center, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Nilsson, K. Peter R.
    Department of Chemistry IFM, Linköping University, Linköping, Sweden.
    Edlund, Ulrica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
    Richter-Dahlfors, Agneta
    Swedish Medical Nanoscience Center, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Stereochemical Identification of Glucans by a Donor-Acceptor-Donor Conjugated Pentamer Enables Multi-Carbohydrate Anatomical Mapping in Plant Tissues2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 7, p. 4253-4264Article in journal (Refereed)
    Abstract [en]

    Optotracing is a novel method for analytical imaging of carbohydrates in plant and microbial tissues. This optical method applies structure-responsive oligothiophenes as molecular fluorophores emitting unique optical signatures when bound to polysaccharides. Herein, we apply Carbotrace680, a short length anionic oligothiophene with a central heterocyclic benzodithiazole (BTD) motif, to probe for different glucans. The donor-acceptor-donor type electronic structure of Carbotrace680 provides improved spectral properties compared to oligothiophenes due to the possibility of intramolecular charge-transfer transition to the BTD motif. This enables differentiation of glucans based on the glycosidic linkage stereochemistry. Thus -configured starch is readily differentiated from -configured cellulose. The versatility of optotracing is demonstrated by dynamic monitoring of thermo-induced starch remodelling, shown in parallel by spectrophotometry and microscopy of starch granules. Imaging of Carbotrace680 bound to multiple glucans in plant tissues provided direct identification of their physical locations, revealing the spatial relationship between structural (cellulose) and storage (starch) glucans at sub-cellular scale. Our work forms the basis for the development of superior optotracers for sensitive detection of polysaccharides. Our non-destructive method for anatomical mapping of glucans in biomass will serve as an enabling technology for developments towards efficient use of plant-derived materials and biomass.

  • 20.
    Ciftci, Göksu Cinar
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Riazanova, Anastasiia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Øvrebø, H.H.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Tailoring of rheological properties and structural polydispersity effects in microfibrillated cellulose suspensions2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 16, p. 9227-9241Article in journal (Refereed)
    Abstract [en]

    Abstract: Industrial production of low-charge microfibrillated cellulose (MFC) typically results in wide fibril size distributions. This polydispersity influences viscosity, overall colloidal stability, and rheological properties of MFC suspensions and gels in aqueous systems. In this work, a systematic rheological analysis is performed for industrially prepared MFC and fractions of different size distributions. Gel formation and flow characteristics (e.g., shear-thinning) of each fraction are examined under neutral and acidic conditions and compared with the unfractionated MFC suspension. The effects of size, aspect ratio, and surface charge on the rheology of semi-dilute MFC suspensions are discussed. The results demonstrate that particle size and aspect ratio distribution control the viscoelasticity and shear-thinning properties of MFC suspensions. An increased fraction of small diameter nanofibrils, by ex situ addition of the fine particles with high aspect ratio or removal of the coarsest particles (with lower aspect ratio) by fractionation, significantly enhances the storage modulus and the yield stress of the complex mixture, compared to the properties of the coarser fractions. New insights are also reported on the tailoring of the rheology of highly polydisperse fibrillar mixtures, where the rheological contributions of each fraction are discussed. Graphic abstract: [Figure not available: see fulltext.].

  • 21. Colombani, A.
    et al.
    Djerbi, Soraya
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Bessueille, L.
    Blomqvist, Kristina
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Ohlsson, Anna
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Berglund, Torkel
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Teeri, Tuula
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Bulone, V.
    In vitro synthesis of (1→3)-β-D-glucan (callose) and cellulose by detergent extracts of membranes from cell suspension cultures of hybrid aspen2004In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 3-4, p. 313-327Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to optimize the conditions for in vitro synthesis of (1 --> 3)-beta-D-glucan (callose) and cellulose, using detergent extracts of membranes from hybrid aspen (Populus tremula x tremuloides) cells grown as suspension cultures. Callose was the only product synthesized when CHAPS extracts were used as a source of enzyme. The optimal reaction mixture for callose synthesis contained 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 8 mM Ca2+, and 20 mM cellobiose. The use of digitonin to extract the membrane-bound proteins was required for cellulose synthesis. Yields as high as 50% of the total in vitro products were obtained when cells were harvested in the stationary phase of the growth curve, callose being the other product. The optimal mixture for cellulose synthesis consisted of 100 mM Mops buffer pH 7.0, 1 mM UDP-glucose, 1 mM Ca2+, 8 mM Mg2+, and 20 mM cellobiose. The in vitro beta-glucans were identified by hydrolysis of radioactive products, using specific enzymes. C-13-Nuclear magnetic resonance spectroscopy and transmission electron microscopy were also used for callose characterization. The (1-->3)-beta-D-glucan systematically had a microfibrillar morphology, but the size and organization of the microfibrils were affected by the nature of the detergent used for enzyme extraction. The discussion of the results is included in a short review of the field that also compares the data obtained with those available in the literature. The results presented show that the hybrid aspen is a promising model for in vitro studies on callose and cellulose synthesis.

  • 22.
    Cunha, Ana Gisela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. INNVENTIA AB, Sweden.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Topochemical acetylation of cellulose nanopaper structures for biocomposites: mechanisms for reduced water vapour sorption2014In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 4, p. 2773-2787Article in journal (Refereed)
    Abstract [en]

    Moisture sorption decreases dimensional stability and mechanical properties of polymer matrix biocomposites based on plant fibers. Cellulose nanofiber reinforcement may offer advantages in this respect. Here, wood-based nanofibrillated cellulose (NFC) and bacterial cellulose (BC) nanopaper structures, with different specific surface area (SSA), ranging from 0.03 to 173.3 m(2)/g, were topochemically acetylated and characterized by ATR-FTIR, XRD, solid-state CP/MAS C-13-NMR and moisture sorption studies. Polymer matrix nanocomposites based on NFC were also prepared as demonstrators. The surface degree of substitution (surface-DS) of the acetylated cellulose nanofibers is a key parameter, which increased with increasing SSA. Successful topochemical acetylation was confirmed and significantly reduced the moisture sorption in nanopaper structures, especially at RH = 53 %. BC nanopaper sorbed less moisture than the NFC counterpart, and mechanisms are discussed. Topochemical NFC nanopaper acetylation can be used to prepare moisture-stable nanocellulose biocomposites.

  • 23. Djahedi, Cyrus
    et al.
    Bergenstrahle-Wohlert, Malin
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Role of hydrogen bonding in cellulose deformation: the leverage effect analyzed by molecular modeling2016In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2315-2323Article in journal (Refereed)
  • 24.
    Djerbi, Soraya
    et al.
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Aspeborg, Henrik
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Nilsson, Peter
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Blomqvist, Kristina
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Teeri, Tuula
    KTH, Superseded Departments (pre-2005), Biotechnology.
    Identification and expression analysis of genes encoding putative cellulose synthases (CesA) in the hybrid aspen, Populus tremula (L.) × P. tremuloides (Michx.)2004In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 3-4, p. 301-312Article in journal (Refereed)
    Abstract [en]

    Cellulose is synthesized in plant cell walls by large membrane-bound protein complexes proposed to contain several copies of the catalytic subunit of the cellulose synthase, CesA. Here we report identification of 10 distinct CesA genes within a database of 100,000 ESTs of the hybrid aspen, Populus tremula (L.) x P. tremuloides (Michx.). Expression analyses in normal wood undergoing xylogenesis and in tension wood indicate xylem specific expression of four putative CesA isoenzymes, PttCesA1, PttCesA3-1, PttCesA3-2 and PttCesA9. Both the protein sequences and the expression profiles of PttCesA3-1 and PttCesA3-2 are very similar, and they may thus represent redundant copies of an enzyme with essentially the same function. Further, one of the generally more constitutively expressed CesA genes, PttCesA2, seems to be activated on the opposite side of a tension wood induced stem, while PttCesA6 appears to be more specific for leaf tissues. The rest of the hybrid aspen CesA genes were found to be relatively evenly expressed over the poplar tissues hereby studied.

  • 25.
    Enebro, Jonas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Momcilovic, Dane
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Siika-Aho, Matti
    VTT Technical Research Center of Finland, Espoo.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Investigation of endoglucanase selectivity on carboxymethyl cellulose by mass spectrometric techniques2009In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, no 2, p. 271-280Article in journal (Refereed)
    Abstract [en]

    The benefits of applying cellulose selective enzymes as analytical tools for chemical structure characterization of cellulose derivatives have been frequently addressed over the years. In a recent study the high selectivity of cellulase Cel45A from Trichoderma reesei (Tr Cel45A) was utilized for relating the chemical structure to the flow properties of carboxymethyl cellulose (CMC). However, in order to take full advantage of the enzymatic hydrolysis the enzyme selectivity on the cellulose substrate must be further investigated. Therefore, the selectivity of Tr Cel45A on CMC was studied by chemical sample preparation of the enzyme products followed by mass spectrometric chemical structure characterization. The results strongly suggest that, in accordance with recent studies, also this highly selective endoglucanase is able to catalyze hydrolysis of glucosidic bonds adjacent to mono-substituted anhydroglucose units (AGUs). Furthermore, the results also indicate that substituents on the nearby AGUs will affect the hydrolysis.

  • 26. Esteves, Cláudia S. V. G.
    et al.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Brännvall, Elisabet
    RISE.
    Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on chemical and physical properties2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Cellulose, Vol. 28, no 5, p. 3149-3167Article in journal (Refereed)
    Abstract [en]

    The fiber properties after oxygen delignification and kraft pulping were studied by looking into the chemical characteristics and morphology. The effect of the two processes on the fibers was evaluated and compared over a wider kappa number range (from 62 down to15). Wide-angle X-ray scattering, nuclear magnetic resonance and fiber saturation point were used to characterize the fiber network structure. Fiber morphology and fiber dislocations were evaluated by an optical image analysis. The total and surface fiber charges were studied by conductometric and polyelectrolyte titrations. The fiber wall supramolecular structure, such as crystallinity, size of fibril aggregates, pore size and pore volume, were similar for the two processes. The selectivity, in terms of carbohydrate yield, was equal for kraft cooking and oxygen delignification, but the selectivity in terms of viscosity loss per amount of delignification is poorer for oxygen delignification. Clearly more fiber deformations (2–6% units in curl index) in the fibers after oxygen delignification were seen. Introduction of curl depended on the physical state of the fibers, i.e. liberated or in wood matrix. In the pulping stage, the fiber continue to be supported by neighboring fibers, as the delignified chips maintain their form. However, in the subsequent oxygen stage the fibers enter in the form of pulp (liberated fibers), which makes them more susceptible to changes in fiber form.

  • 27.
    Esteves, Cláudia S. V. G.
    et al.
    RISE INNVENTIA AB, Drottning Kristinas Vag 61, S-11428 Stockholm, Sweden..
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Brännvall, Elisabet
    RISE INNVENTIA AB, Drottning Kristinas Vag 61, S-11428 Stockholm, Sweden..
    Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on mechanical properties2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 6, p. 3775-3788Article in journal (Refereed)
    Abstract [en]

    Charged groups in pulp have been shown to enhance the tensile strength of the paper produced from the pulp. Oxygen delignification introduces charged groups and it is of interest to determine how the delignification should be distributed between the cooking and the oxygen stage with respect to mechanical properties. A number of unbleached kraft cooked and oxygen delignified pulps within a wide kappa number range were produced and refined, and the effects of the refining on the morphology and mechanical properties were studied. The WRV correlated with the fiber charge and at a given fiber charge, kraft cooked and oxygen delignified pulps had the same WRV development in refining, although they had significantly different kappa numbers. The tensile strength development during refining depends on the fiber rigidity which is affected by the lignin content, the fiber charge and the chemical and mechanical processes used. Refining increased the curl of the kraft cooked pulps and decreased the curl of oxygen delignified pulps, irrespective of kappa number. A greater increase in tensile strength was seen for the pulps with a higher fiber charge and WRV, probably because of the greater degree of fibrillation achieved in the beating process. Despite the greater fiber deformation in the oxygen delignified pulps, the strength can be increased by a larger amount of charged groups and a greater swelling of the fibers.

  • 28. Falt, S.
    et al.
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Vesterlind, E. L.
    Larsson, Per Tomas
    Model films of cellulose II - improved preparation method and characterization of the cellulose film2004In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, no 2, p. 151-162Article in journal (Refereed)
    Abstract [en]

    An optimization study of the preparation of spin-coated cellulose model films from the NMMO/DMSO system on silicon wafers has been made. The study shows that the cellulose concentration in the solution determines the cellulose film thickness and that the temperature of the solution affects the surface roughness. A lower solution temperature results in a lower surface roughness at cellulose concentrations below 0.8%. Using the described method, it is possible to prepare films with thicknesses of 30-90 nm with a constant surface roughness by changing the cellulose concentration, i.e. by dilution with DMSO. On these films, water has a contact angle less than 20degrees and about 50% of the material can, according to CP/MAS C-13-NMR spectroscopy on corresponding fibrous material, be considered to consist of crystalline cellulose II type material. It has further been shown that AFM can be used to determine the thickness of cellulose films, in both dry and wet states. In this method, the difference in height between the top surface and the underlying wafer has been measured at an incision made into the cellulose film. The cellulose films have also been spin-coated with the same technique as on the silicon oxide wafer onto the crystal in a quartz crystal microbalance (QCM). These model films were found to be suitable for swelling measurements with the QCM. The films were very stable during this type of measurement and films with different amounts of charges gave different swelling responses depending on their charges. As expected, films with a higher charge showed a higher swelling.

  • 29. Forsberg, D. C. R.
    et al.
    Westin, P. -O
    Li, Lengwan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Svedberg, A.
    Grundberg, H.
    Berglund, Lars A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    A method for chemical and physical modification of oriented pulp fibre sheets2022In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 29, no 15, p. 8371-8386Article in journal (Refereed)
    Abstract [en]

    Wood pulp fibres are promising reinforcements for biocomposites due to their renewable resource origin and mechanical properties. An oriented and dense fibre reinforcement structure is beneficial for biocomposite properties. We present a method of modifying fibres (e.g. to increase strain to failure) in pre-formed oriented high-density paper structures intended for biocomposites or as hot-pressed fibre materials. Mildly delignified, well-preserved holocellulose fibres from softwood are used. Cold alkali treatment (hemicellulose removal) and mercerisation (conversion to cellulose II) were carried out successfully on oriented fibre sheets. Controlled anisotropy and sheet density are achieved from untreated and straight fibres in the sheet formation step. High mechanical properties and increased ductility of mercerised sheets were observed, which may be valuable for hot-pressed fibre materials (E ≈ 7.1 GPa, strength of 108 MPa and strain to failure of 5.3%) and biocomposites. In contrast, modified wood pulp fibres were difficult to orient, resulting in higher sheet porosity and weak interfibre bonding.

  • 30.
    Garcia-Garcia, Daniel
    et al.
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Balart, Rafael
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Lopez-Martinez, Juan
    UPV, ITM, Plaza Ferrandiz y Carbonell 1, Alicante 03801, Spain..
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Moriana, Rosana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 5, p. 2925-2938Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNCs) were isolated for the first time from pine cones (PC) by alkali and bleaching treatments and subsequent sulfuric acid hydrolysis (64%) at 45 degrees C. The influence of the hydrolytic reaction time (30, 45, and 90 min) on the yield, chemical composition and structure, and thermal stability of CNCs was evaluated. The removal of non-cellulosic constituents during the alkaline and bleaching treatment resulted in high pure cellulosic fibres. The isolation of CNCs from these cellulosic fibres at different reaction times was verified by the nano-dimensions of the individual crystals (< 3 and < 335 nm of average diameter and length, respectively). The highest yield (15%) and the optimum CNCs properties in terms of aspect ratio, thermal stability and crystallinity were obtained for an extraction time of 45 min. PC appeared to be a new promising source of cellulose fibres and CNCs with potential to be applied as reinforcement in composites and for food-packaging.

  • 31. Garg, M.
    et al.
    Apostolopoulou-Kalkavoura, V.
    Linares, M.
    Kaldéus, Tahani
    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.
    Malmström, Eva
    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, Coating Technology.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, 106 91, Stockholm, Sweden;Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56-58, 100 44, Stockholm, Sweden. .
    Zozoulenko, I.
    Moisture uptake in nanocellulose: the effects of relative humidity, temperature and degree of crystallinity2021In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 28, no 14, p. 9007-9021Article in journal (Refereed)
    Abstract [en]

    Foams made from cellulose nanomaterials are highly porous and possess excellent mechanical and thermal insulation properties. However, the moisture uptake and hygroscopic properties of these materials need to be better understood for their use in biomedical and bioelectronics applications, in humidity sensing and thermal insulation. In this work, we present a combination of hybrid Grand Canonical Monte Carlo and Molecular Dynamics simulations and experimental measurements to investigate the moisture uptake within nanocellulose foams. To explore the effect of surface modification on moisture uptake we used two types of celluloses, namely TEMPO-oxidized cellulose nanofibrils and carboxymethylated cellulose nanofibrils. We find that the moisture uptake in both the cellulose nanomaterials increases with increasing relative humidity (RH) and decreases with increasing temperature, which is explained using the basic thermodynamic principles. The measured and calculated moisture uptake in amorphous cellulose (for a given RH or temperature) is higher as compared to crystalline cellulose with TEMPO- and CM-modified surfaces. The high water uptake of amorphous cellulose films is related to the formation of water-filled pores with increasing RH. The microscopic insight of water uptake in nanocellulose provided in this study can assist the design and fabrication of high-performance cellulose materials with improved properties for thermal insulation in humid climates or packaging of water sensitive goods. Graphic abstract: [Figure not available: see fulltext.]

  • 32. Gellerstedt, F.
    et al.
    Wågberg, Lars
    Gatenholm, P.
    Swelling behaviour of succinylated fibers2000In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 7, no 1, p. 67-86Article in journal (Refereed)
    Abstract [en]

    The swelling behaviour of cellulosic fibers bearing various amounts of carboxylic groups introduced by succinylation was studied as a function of pH. Upon an increase of pH, the perimeter of the succinylated fibers expanded as measured with the Wilhelmy plate technique. The fibers pass two pH regimes of increased expansion, pH = 5 and pH = 9. These pH levels correlate with the conductometric titration, which reveals two inflection points in both the pH and conductivity values for the succinylated fibers. Determinations of fiber saturation points (FSP) confirm that the cell wall is largely affected by increased pH. Analysis of the fibers with ESEM (Environmental Scanning Electron Microscope) showed that bundles of fibrils were released from the surface of the succinylated fibers at higher pH. Wilhelmy measurements also showed that the surface roughness was more than doubled in fibers succinylated for 12 h as pH rose from 3.2 to 10. These results indicate that, as the charge of the fibers is increased, the swelling forces reach such levels of magnitude that they overcome the structural network forces holding the fiber wall together. The methodology applied can hence be used to quantify the fundamental gel properties of the fiber wall.

  • 33.
    Ghaffari, Roujin
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden; Wallenberg Wood Science Center, Chalmers University of Technology, Gothenburg, Sweden.
    Almqvist, Henrik
    Department of Chemical Engineering, Lund University, Lund, Sweden.
    Idström, Alexander
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden.
    Sapouna, Ioanna
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Glycoscience. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Evenäs, Lars
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden; Wallenberg Wood Science Center, Chalmers University of Technology, Gothenburg, Sweden; Department of Chemistry and Chemical Engineering, FibRe – Centre for Lignocellulose-based Thermoplastics, Chalmers University of Technology, Gothenburg, Sweden.
    Lidén, Gunnar
    Department of Chemical Engineering, Lund University, Lund, Sweden.
    Lawoko, Martin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Larsson, Anette
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg, Sweden; Wallenberg Wood Science Center, Chalmers University of Technology, Gothenburg, Sweden; Department of Chemistry and Chemical Engineering, FibRe – Centre for Lignocellulose-based Thermoplastics, Chalmers University of Technology, Gothenburg, Sweden.
    Effect of alkalinity on the diffusion of solvent-fractionated lignin through cellulose membranes2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 30, no 6, p. 3685-3698Article in journal (Refereed)
    Abstract [en]

    Mass transport of liberated lignin fragments from pits and fiber walls into black liquor is considered a determining step in the delignification process. However, our current understanding of the diffusion of lignin through cellulose and the influential parameter on this process is very limited. A comprehensive and detailed study of lignin mass transport through cellulosic materials is, therefore, of great importance. In this study, diffusion cell methodology is implemented to systematically investigate the transport of fractionated kraft lignin molecules through model cellulose membranes. Pulping is a complex process and lignin is very heterogenous material therefore to perform a more detailed study on lignin diffusion, we included an additional solvent fractionation step. One of the benefits of this method is that the setup can be adjusted to various experimental conditions allowing the complex chemical reactions occurring during pulping, which would affect the mass transfer of lignin, to be avoided. Here, the effects of the alkalinity of the aqueous solution and molecular weight of the kraft lignin molecules on their diffusion were investigated. Additionally, NMR spectroscopy, size exclusion chromatography, and UV/Vis spectroscopy were used to characterize the starting material and the molecules that passed through the membrane. Lignin molecules detected in the acceptor chamber of the diffusion cells had lower molecular weights, indicating a size fractionation between the donor and acceptor chamber. UV/Vis showed higher concentrations of ionized conjugated kraft lignin molecules in the acceptor chamber, which is a sign of chemical fractionation. This study suggests that the diffusion of lignin through small cellulose pores can be enhanced by decreasing the average molecular weight of the diffusing kraft lignin molecules and increasing alkalinity.

  • 34.
    Gimåker, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Adsorption of polyallylamine to lignocellulosic fibres: effect of adsorption conditions on localisation of adsorbed polyelectrolyte and mechanical properties of resulting paper sheets2009In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 16, no 1, p. 87-101Article in journal (Refereed)
    Abstract [en]

    Cationic polyallylamine (PAH), was adsorbed onto lignocellulosic fibres, and a fluorescent label on the polyelectrolyte enabled its location to be shown by confocal fluorescence microscopy. The adsorption time and ionic strength were varied to study their effect on the localisation of the adsorbed PAH. The microscopy showed that a long adsorption time, 24 h, and a high ionic strength, 10(-1) M NaCl + 5 x 10(-3) M NaHCO3 or higher, resulted in the adsorption of polyallylamine throughout the fibre walls. Shorter adsorption times and/or lower ionic strength resulted in adsorption only to the fibre exterior. By preparing sheets from fibres with polyelectrolyte adsorbed either to the exterior parts or into the fibre cell wall and testing their mechanical behaviour, a link was established between the localisation of adsorbed polyelectrolyte and the mechanical properties. Adsorption to the fibre exterior led to an increase in tensile strength and strain at break. The creep deformation at 90%RH was also slightly reduced by the adsorption of low molecular weight PAH (15 kDa). When polyallylamine was adsorbed throughout the wall of the lignocellulosic fibres, the mechanical properties were not however improved and the creep deformation at 90%RH actually increased somewhat.

  • 35.
    Goliszek, M.
    et al.
    Marie Curie Sklodowska Univ, Fac Chem, Maria Curie Sklodowska Sq 3, PL-20031 Lublin, Poland..
    Podkoscielna, B.
    Marie Curie Sklodowska Univ, Fac Chem, Maria Curie Sklodowska Sq 3, PL-20031 Lublin, Poland..
    Fila, K.
    Marie Curie Sklodowska Univ, Fac Chem, Maria Curie Sklodowska Sq 3, PL-20031 Lublin, Poland..
    Riazanova, Anastasia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Aminzadeh, Selda
    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.
    Sevastyanova, O.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Gun'ko, V. M.
    Chuiko Inst Surface Chem, 17 Gen Naumov Str, UA-03164 Kiev, Ukraine..
    Synthesis and structure characterization of polymeric nanoporous microspheres with lignin2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 10, p. 5843-5862Article in journal (Refereed)
    Abstract [en]

    Nanoporous microspheres with divinylbenzene (DVB), styrene (St), and lignin were synthesized by an emulsion-suspension polymerization method. Several types of lignins were used: (1) kraft lignin before (L-unmod) and after modification with methacryloyl chloride (L-Met) and (2) low-molecular-weight kraft lignin unmodified (LWL-unmod) and modified with methacrylic anhydride (LWL-Met). LWL was prepared by ultrafiltration of industrial black liquor using a ceramic membrane with a molecular weight (Mw) cut-off of 5 kDa. The synthesis was optimized by addition of different amounts of lignins. The microsphere texture was characterized using low-temperature nitrogen adsorption and small angle X-ray scattering analyses. The microspheres were nano- and mesoporous with a specific surface area in the range of 0.1-409 m(2)/g. The morphology of the copolymers was studied using field emission scanning electron microscopy and atomic force microscopy. The thermal properties were studied using differential scanning calorimetry and thermogravimetric analysis methods. A significant difference in the microsphere roughness is affected by lignins due to the presence of lignin nanoparticles at the surface of the microspheres. Molecular modeling was used to predict the sorption properties of the copolymers affected by various fields around the particles. The particle size, polydispersity and zeta potential of the St + DVB, L-Met + St + DVB and L-unmod + St + DVB samples were measured by dynamic light scattering. Additionally, the point of zero charge of the samples was determined using potentiometric titration. The materials studied have a great potential for sorption processes due to their developed porosity and the presence of a number of active surface functionalities. [GRAPHICS] .

  • 36. Gunnars, S.
    et al.
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Pulp and Paper Technology.
    Stuart, M. A. C.
    Model films of cellulose: I. Method development and initial results2002In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 9, no 04-mar, p. 239-249Article in journal (Refereed)
    Abstract [en]

    This report presents a new method for the preparation of thin cellulose films. NMMO (N- methylmorpholine- N-oxide) was used to dissolve cellulose and addition of DMSO (dimethyl sulfoxide) was used to control viscosity of the cellulose solution. A thin layer of the cellulose solution is spin- coated onto a silicon oxide wafer and the cellulose is precipitated in deionised water. The cellulose film is anchored onto the silicon oxide wafer by a saturated polymer layer. Among many different polymers tested, PVAm (polyvinylamine) and G- PAM (glyoxalated- polyacrylamide) worked well. The preparation of cellulose model films described in this paper resulted in films with thicknesses in the range 20- 270 nm and the thickness can be controlled by altering the concentration of cellulose solution by addition of different amounts of DMSO. The films were cleaned in deionised water and were found to be free from solvents by ESCA analysis and contact angle measurements. The molecular weight distribution of the cellulose surface material shows that there is only minor breakdown of the cellulose chains, mainly by cleavage of the longest molecular mass fraction and without creation of low molecular mass oligomers of glucose.

  • 37.
    Gunnarsson, Maria
    et al.
    Chalmers Univ Technol, Dept Chem & Chem Engn, Div Forest Prod & Chem Engn, S-41296 Gothenburg, Sweden..
    Hasani, Merima
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Dept Chem & Chem Engn, Div Forest Prod & Chem Engn, S-41296 Gothenburg, Sweden.
    Bernin, Diana
    Chalmers Univ Technol, Dept Chem & Chem Engn, Div Chem React Engn, S-41296 Gothenburg, Sweden..
    Influence of urea on methyl beta-D-glucopyranoside in alkali at different temperatures2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 18, p. 9413-9422Article in journal (Refereed)
    Abstract [en]

    The dissolution efficiency plays an important role on the properties of regenerated cellulose-based products. Urea is known to be one of the additives aiding to improve cellulose dissolution in the NaOH(aq) system. The acting mechanism caused by urea has been debated and one of the hypothesis is that urea could induce a conformational change on cellulose, which promotes dissolution. Here we used NMR spectroscopy on a model system for cellulose, namely, methyl beta-D-glucopyranoside (beta-MeO-Glcp) and compared chemical shifts and J couplings, which both are indicators for conformational changes, as a function of temperature and upon the addition of urea. We found that in NaOH(aq), the hydroxymethyl group changes its conformation in favour of the population of the gt rotamer, while the presence of urea induced temperature dependent conformational changes. Heteronuclear Overhauser effect experiments showed that urea associates with cellulose but in a non-specific manner. This suggests that urea rather than binding to the carbohydrate, changes the chemical environment inducing a change in conformation of beta-MeO-Glcp and likely also for cellulose when dissolved in NaOH(aq) with urea.

  • 38.
    Gunnarsson, Maria
    et al.
    Chalmers Univ Technol, Dept Chem & Chem Engn, Div Forest Prod & Chem Engn, SE-41296 Gothenburg, Sweden..
    Hasani, Merima
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Stockholm, SE-100 44, Sweden.
    Bernin, Diana
    Chalmers Univ Technol, Dept Chem & Chem Engn, Div Chem React Engn, SE-41296 Gothenburg, Sweden..
    The potential of magnetisation transfer NMR to monitor the dissolution process of cellulose in cold alkali2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 18, p. 9403-9412Article in journal (Refereed)
    Abstract [en]

    Cellulose is the most important biopolymer on earth and, when derived from e.g. wood, a promising alternative to for example cotton, which exhibits a large environmental burden. The replacement depends, however, on an efficient dissolution process of cellulose. Cold aqueous alkali systems are attractive but these solvents have peculiarities, which might be overcome by understanding the acting mechanisms. Proposed dissolution mechanisms are for example the breakage of hydrophobic interactions and partly deprotonation of the cellulose hydroxyl groups. Here, we performed a mechanistic study using equimolar aqueous solutions of LiOH, NaOH and KOH to elucidate the dissolution process of microcrystalline cellulose (MCC). The pH was the highest for KOH(aq) followed by NaOH(aq) and LiOH(aq). We used a combination of conventional and advanced solution-state NMR methods to monitor the dissolution process of MCC by solely increasing the temperature from - 10 to 5 degrees C. KOH(aq) dissolved roughly 25% of the maximum amount of MCC while NaOH(aq) and LiOH(aq) dissolved up to 70%. Water motions on nanoscale timescales present in non-frozen water, remained unaffected on the addition of MCC. Magnetisation transfer (MT) NMR experiments monitored the semi-rigid MCC as a function of temperature. Interestingly, although NaOH(aq) and LiOH(aq) were able to dissolve a similar amount at 5 degrees C, MT spectra revealed differences with increasing temperature, suggesting a difference in the swollen state of MCC in LiOH(aq) already at - 10 degrees C. Furthermore, MT NMR shows a great potential to study the water exchange dynamics with the swollen and semi-rigid MCC fraction in these systems, which might give valuable insights into the dissolution mechanism in cold alkali.

  • 39. Gunnarsson, Maria
    et al.
    Theliander, Hans
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Hasani, Merima
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Chemisorption of air CO2 on cellulose: an overlooked feature of the cellulose/NaOH(aq) dissolution system2017In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 6, p. 2427-2436Article in journal (Refereed)
    Abstract [en]

    A natural abundance of the air CO2 in NaOH(aq) at low temperature was investigated in terms of cellulose-CO2 interactions upon cellulose dissolution in this system. An organic superbase, namely 1,8-diazabicyclo[5.4.0]undec-7-ene, DBU, known for its ability to incorporate CO2 in carbohydrates, was employed in order to shed light on this previously overlooked feature of NaOH(aq) at low temperature. The chemisorption of CO2 onto cellulose was investigated using spectroscopic methods in combination with suitable regeneration procedures. ATR-IR and NMR characterisation of regenerated celluloses showed that chemisorption of CO2 onto cellulose during its dissolution in NaOH(aq) takes place both with and without employment of the CO2-capturing superbase. The chemisorption was also observed to be reversible upon addition of water: CO2 desorbed when water was used as regenerating agent but could be preserved when instead ethanol was used. This finding could be an important parameter to take into consideration when developing processes for dissolution of cellulose based on this system.

  • 40.
    Guo, Lifang
    et al.
    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.
    Lennholm, Helena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Zhai, H.
    Ek, Monica
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Structural and functional modification of cellulose nanofibrils using graft copolymerization with glycidyl methacrylate by Fe 2+ –thiourea dioxide–H 2 O 2 redox system2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 8, p. 4853-4864Article in journal (Refereed)
    Abstract [en]

    Abstract: To graft epoxy and ester functional groups onto cellulose nanofibrils (CNFs) and to overcome their poor hydrophobicity, we studied the modification of CNFs using graft copolymerization with glycidyl methacrylate (GMA) by a Fe 2+ –thiourea dioxide–H 2 O 2 initiator system (Fe 2+ –TD–H 2 O 2 ) in aqueous solution. The synthesized poly (GMA)-grafted CNF (CNF-g-PGMA) was characterized by FTIR, AFM, XRD, water contact angle, and TGA. GMA was successfully grafted onto the CNFs by Fe 2+ –TD–H 2 O 2 , the epoxy groups and ester groups of GMA were clearly present and intact in the CNF-g-PGMA, and TD is an important component of the initiator system under relatively mild graft conditions. CNF-g-PGMA may be an important intermediate because of its epoxy and ester functional groups. The main nanostructure of the CNFs was retained after graft copolymerization, and there were no obvious effects of graft copolymerization on the crystalline structure of the CNF backbone, although the crystalline index slightly decreased with the increased percentage of grafting. Graft copolymerization significantly modifies the CNF hydrophobicity. This strategy could extend the applications of CNFs into many areas. Graphical abstract: [Figure not available: see fulltext.]

  • 41.
    Halonen, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Iversen, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mercerized cellulose biocomposites: A study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties2013In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 1, p. 57-65Article in journal (Refereed)
    Abstract [en]

    In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS 13C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.

  • 42. Halysh, V.
    et al.
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Pikus, S.
    Dobele, G.
    Pasalskiy, B.
    Gun´ko, V. M.
    Kartel, M.
    Sugarcane bagasse and straw as low-cost lignocellulosic sorbents for the removal of dyes and metal ions from water2020In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 27, no 14, p. 8181-8197Article in journal (Refereed)
    Abstract [en]

    Abstract: Sugarcane bagasse (stalk) and straw (leaves), an agricultural waste, which had been subjected to either an organosolv or organosolv-oxidative pretreatment were used for the removal of methylene blue dye or heavy metals (Fe(III) and Cu(II)) from model aqueous solutions. The sorption of methylene blue was investigated as a function of pH, dye concentration, and contact time. The sorption of metal ions was studied as a function of concentration. Classical Langmuir and Freundlich adsorption models were used to analyze the sorption process. It was shown that adsorption isotherms fitted better into Freundlich isotherm model, which assumes a multilayer adsorption on a heterogeneous surface. The morphological, textural, and structural characteristics such as bulk and true densities, particle size distributions, porosity, and thermal decomposition features of the biosorbents were determined to understand better the mechanism of sorption of various pollutants. The results showed significant differences in the chemical compositions and physical properties of the initial and modified biomass samples, especially for the cellulosic biosorbents prepared with organosolv-oxidative pretreatment. For the removal of dyes, the development of a pore structure as a result of the pretreatment seemed to play an important role, while the sorption of metals was strongly dependent on the chemical composition of the biosorbent. The highest adsorption capacity for methylene blue and for Fe(III) and Cu(II) was obtained for a lignocellulosic sorbent from sugarcane straw prepared by organosolv pretreatment. The results obtained confirm a great potential use of agricultural waste from sugarcane industry in wastewater treatment. 

  • 43.
    Halysh, Vita
    et al.
    Igor Sikorsky Kyiv Polytech Inst, Fac Chem Engn, Dept Ecol & Technol Plant Polymers, Peremogy Avenu 37-4, UA-03056 Kiev, Ukraine.;Natl Acad Sci Ukraine, OO Chuiko Inst Surface Chem, Gen Naumov Str 17, UA-03164 Kiev, Ukraine..
    Sevastyanova, Olena
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Riazanova, Anastasia
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Pasalskiy, Bogdan
    Kyiv Natl Univ Trade & Econ, Kyoto Str 19, UA-02156 Kiev, Ukraine..
    Budnyak, Tetyana
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. Natl Acad Sci Ukraine, OO Chuiko Inst Surface Chem, Gen Naumov Str 17, UA-03164 Kiev, Ukraine..
    Lindström, Mikael
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Kartel, Mykola
    Natl Acad Sci Ukraine, OO Chuiko Inst Surface Chem, Gen Naumov Str 17, UA-03164 Kiev, Ukraine..
    Walnut shells as a potential low-cost lignocellulosic sorbent for dyes and metal ions2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 8, p. 4729-4742Article in journal (Refereed)
    Abstract [en]

    Currently, it is necessary to develop new methods and materials for solving the problem of environmental pollution by various toxicants. For these purposes, vegetal materials can be used. In this study, efficient low-cost sorbents based on walnut shells, an agro-industrial by-product, were prepared by treatment with acetic acid or a mixture of acetic acid and hydrogen peroxide. It was shown that the treatments significantly affected the composition and structure of walnut shells and their sorption properties with respect to organic dyes (methylene blue, methyl violet, and murexide) and heavy metal ions. Methylene blue dye was used for additional studies on the effect of pH, contact time and kinetics of sorption. The maximum adsorption rate of the dye occurred within the first 30 min of contact, during which the concentration of methylene blue in the solution was reduced by more than half. Full sorption equilibrium was reached within 180-230 min for studied samples. The adsorption kinetics of methylene blue was found to best be described by pseudo-second-order kinetic model. It was shown that dyes adsorption processes were well described by Freundlich model, which takes into consideration the heterogeneity of the surface of the adsorbent. The obtained plant sorbents are characterized by a high sorption capacity for heavy metal ions (18-29 mg/g for Fe3+ and 33-44 mg/g for Cu-2). Due to their numerous advantages, such as the high sorption capacity, high availability and low cost of raw materials, simplicity of disposal and nontoxicity, the obtained natural sorbents may have a wide practical use in industrial wastewater treatment. [GRAPHICS] .

  • 44.
    Han, Xiao
    et al.
    State Key Laboratory of Chemical Engineering, Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People’s Republic of China.
    Chen, Pan
    School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, People’s Republic of China.
    Li, Lengwan
    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, Biocomposites.
    Nishiyama, Yoshiharu
    University Grenoble Alpes, CNRS, CERMAV, 38000, Grenoble, France.
    Yang, Xuan
    State Key Laboratory of Chemical Engineering, Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, People’s Republic of China; Institute of Zhejiang University, Quzhou, 324000, People’s Republic of China.
    Planar and uniplanar orientation in nanocellulose films: interpretation of 2D diffraction patterns step-by-step2023In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 30, no 13, p. 8151-8159Article in journal (Refereed)
    Abstract [en]

    X-ray diffraction (XRD) is widely used in cellulose structural characterization. The commonly used “powder” XRD assumes the sample is macroscopically isotropic. For cellulose fibrous samples, however, due to the high aspect ratio of the components, the structure is often anisotropic, and the texture affects the materials properties to a large extent. A simple setup of a point-focused X-ray beam and a two-dimensional detection of scattered X-ray is a practical tool to analyze the texture. We studied three types of cellulose nanofibril (CNF) films obtained by casting. 2,2,6,6-tetramethylpiper- idine-1-oxyl radical (TEMPO) oxidized one shows a high degree of (1–10) uniplanar orientation, whereas holocellulose CNF and enzyme-pretreated CNF showed planar orientation. In the planar orientation, the c-axis is preferentially oriented in the plane parallel to the film while within each fibril other crystallographic axis would be randomly distributed around the c-axis. Also, a clear peak can be detected at low angle corresponding to a d-spacing of 3–4 nm indicating a strong correlation perpendicular to the film at this length scale. This distance was the lowest for TEMPO-CNF and corroborates with the model of uniplanar orientation of rectangular cross-section. The numerically simulated azimuthal intensity distribution of hk0 reflections in the two types of texture agreed well with the experimental intensity distribution.

  • 45. Hansen, Natanya M. L.
    et al.
    Blomfeldt, Thomas O. J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Plackett, David V.
    Properties of plasticized composite films prepared from nanofibrillated cellulose and birch wood xylan2012In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 19, no 6, p. 2015-2031Article in journal (Refereed)
    Abstract [en]

    Xylans, an important sub-class of hemicelluloses, represent a largely untapped resource for new renewable materials derived from biomass. As with other carbohydrates, nanocellulose reinforcement of xylans is interesting as a route to new bio-materials. With this in mind, birch wood xylan was combined with nanofibrillated cellulose (NFC) and films were cast with and without glycerol, sorbitol or methoxypolyethylene glycol (MPEG) as plasticizers. Microscopy revealed some NFC agglomeration in the composite films as well as a layered nanocellulose structure. Equilibrium moisture content in plasticized films increased with glycerol content but was independent of xylan:NFC ratio in unplasticized films. Sorbitol- and MPEG-plasticized films showed equilibrium moisture contents of approximately 10 wt% independent of plasticizer content. Tensile testing revealed increases in tensile strength with increased NFC content in the xylan:NFC composition range from 50:50 to 80:20 and plasticizer addition generally provided less brittle films. The oxygen permeability of unplasticized xylan-NFC films fell into a range which was similar to that for previously measured pure NFC films and was statistically independent of the xylan:NFC ratio. Water vapor permeability values of 1.9-2.8.10(-11) g Pa-1 m(-1) s(-1) were found for unplasticized composite films, but these values were significantly reduced in the case of films plasticized with 10-40 wt% sorbitol.

  • 46.
    Hedlund, Artur
    et al.
    Swerea IVF, Biobased Fibers, Argongatan 30, S-43153 Molndal, Sweden.;Chalmers Univ Technol, Forest Prod & Chem Engn, Gothenburg, Sweden..
    Kohnke, Tobias
    Swerea IVF, Biobased Fibers, Argongatan 30, S-43153 Molndal, Sweden..
    Hagman, Joel
    Lund Univ, Phys Chem, Box 124, S-22100 Lund, Sweden..
    Olsson, Ulf
    Lund Univ, Phys Chem, Box 124, S-22100 Lund, Sweden..
    Theliander, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center. Chalmers Univ Technol, Forest Prod & Chem Engn, Gothenburg, Sweden.;Chalmers Univ Technol, .
    Microstructures of cellulose coagulated in water and alcohols from 1-ethyl-3-methylimidazolium acetate: contrasting coagulation mechanisms2019In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 3, p. 1545-1563Article in journal (Refereed)
    Abstract [en]

    Coagulation of cellulose solutions is a process whereby many useful materials with variable microstructures and properties can be produced. This study investigates the complexity of the phase separation that generates the structural heterogeneity of such materials. The ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]), and a co-solvent, dimethylsulfoxide (DMSO), are used to dissolve microcrystalline cellulose in concentrations from 5 to 25wt%. The solutions are coagulated in water or 2-propanol (2PrOH). The coagulated material is then washed and solvent exchanged (water2PrOHbutanonecyclohexane) in order to preserve the generated microstructures upon subsequent drying before analysis. Sweep electron microscopy images of 50k magnification reveal open-pore fibrillar structures. The crystalline constituents of those fibrils are estimated using wide-angle X-ray spectroscopy and specific surface area data. It is found that the crystalline order or crystallite size is reduced by an increase in cellulose concentration, by the use of the co-solvent DMSO, or by the use of 2PrOH instead of water as the coagulant. Because previous theories cannot explain these trends, an alternative explanation is presented here focused on solid-liquid versus liquid-liquid phase separations. [GRAPHICS] .

  • 47.
    Herrera, Martha
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Thitiwutthisakul, Kasinee
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Yang, Xuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Rujitanaroj, Pim-on
    SCG Packaging Publ Co Ltd, Prod & Technol Dev Ctr, Ban Pong 70110, Ratchaburi, Thailand..
    Rojas, Ramiro
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites.
    Preparation and evaluation of high-lignin content cellulose nanofibrils from eucalyptus pulp2018In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 5, p. 3121-3133Article in journal (Refereed)
    Abstract [en]

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

  • 48.
    Hollertz, Rebecca
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Arwin, Hans
    Faure, Bertrand
    Zhang, Yujia
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Bergström, Lennart
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Dielectric properties of lignin and glucomannan as determined by spectroscopic ellipsometry and Lifshitz estimates of non-retarded Hamaker constants2013In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 4, p. 1639-1648Article in journal (Refereed)
    Abstract [en]

    We present in this study a quantitative estimate of the dispersive interactions between lignin, hemicellulose and cellulose, which are the dominating components in wood and also extensively used to produce paper and packaging materials. The dielectric properties in the UV-visible region of spin-coated films of pure lignin and glucomannan were determined by spectroscopic ellipsometry. The non-retarded Hamaker constants were estimated from the determined spectral parameters using Lifshitz theory for lignin and glucomannan interacting with cellulose, titania and calcium carbonate in vacuum, water and hexane. The Hamaker constants for the different combinations of cellulose, lignin and glucomannan fall within a relatively narrow range of 35-58 and 8-17 zJ, for the values in vacuum (air) and water, respectively. The estimated Hamaker constants for the interactions of the wood components with TiO2 and CaCO3, common additives in paper, in water range from 3 to 19 zJ, thus being similar in magnitude as the interactions between the wood components themselves. In contrast, the Hamaker constant is essentially zero for glucomannan interacting with calcium carbonate in hexane. The Hamaker constants for lignin, hemicellulose and cellulose determined in this study can provide information regarding the surface interactions important for e.g. adhesion, friction, swelling and wetting in paper processing as well as for the resulting behavior of paper products.

  • 49.
    Hollertz, Rebecca
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    López Durán, Vernica
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Chemically modified cellulose micro- and nanofibrils as paper-strength additives2017In: Cellulose, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 9, p. 3883-3899Article in journal (Refereed)
    Abstract [en]

    Chemically modified cellulose micro- and nanofibrils were successfully used as paper strength additives. Three different kinds of cellulose nanofibrils (CNFs) were studied: carboxymethylated CNFs, periodate-oxidised carboxymethylated CNFs and dopamine-grafted carboxymethylated CNFs, all prepared from bleached chemical fibres of dissolving grade, and one microfibrillated cellulose from unbleached kraft fibres. In addition to mechanical characterization of the final paper sheets the fibril retention, sheet density and sheet morphology were also studied as a function of addition of the four different cellulose fibrils. In general, the cellulose fibrils, when used as additives, significantly increased the tensile strength, Young’s modulus and strain-at-break of the paper sheets. The effects of the different fibrils on these properties were compared and evaluated and used to analyse the underlying mechanisms behind the strengthening effect. The strength-enhancing effect was most pronounced for the periodate-oxidised CNFs when they were added together with polyvinyl amine (PVAm) or poly(dimethyldiallylammonium chloride) (pDADMAC). The addition of periodate-oxidised CNFs, with pDADMAC as retention aid, resulted in a 37% increase in tensile strength at a 2 wt% addition and an 89% increase at a 15 wt% addition (from 67 to 92 and 125 kNm/kg, respectively) compared to a reference with only pDADMAC. Wet-strong sheets with a wet tensile index of 30 kNm/kg were also obtained when periodate-oxidised CNFs and PVAm were combined. This significant increase in wet strength is suggested to be the result of a formation of cross-links between the aldehyde groups, introduced by the periodate oxidation, and hydroxyl groups on the lignocellulosic fibres and the primary amines of PVAm. Even though less significant, there was also an increase in wet tensile strength when pDADMAC was used together with periodate-oxidised fibrils which shows that the aldehyde groups are able to increase the wet strength without the presence of the primary amines of the PVAm. As an alternative method to strengthen the fibre network, carboxymethylated CNFs grafted with dopamine, by an ethyl dimethylaminopropyl carbodiimide coupling, were used as a strength additive. When used as an additive, these CNFs showed a strong propensity to form films on and around the fibres and significantly increased the mechanical properties of the sheets. Their addition resulted in an increase in the Young´s modulus by 41%, from 5.1 to 7.2 GPa, and an increase in the tensile strength index of 98% (from 53 to 105 kNm/kg) with 5 wt% retained dopamine-grafted CNFs.

  • 50.
    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, ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 1, p. 665-677Article 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.

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