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  • 1.
    Aadland, Reidun C.
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Dziuba, Carter J.
    University of Calgary, Canada.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    Holt, Thorleif
    SINTEF, Norway.
    Gates, Ian D.
    University of Calgary, Canada.
    Bryant, Steven L.
    University of Calgary, Canada.
    Identification of nanocellulose retention characteristics in porous media2018In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 7, article id 547Article in journal (Refereed)
    Abstract [en]

    The application of nanotechnology to the petroleum industry has sparked recent interest in increasing oil recovery, while reducing environmental impact. Nanocellulose is an emerging nanoparticle that is derived from trees or waste stream from wood and fiber industries. Thus, it is taken from a renewable and sustainable source, and could therefore serve as a good alternative to current Enhanced Oil Recovery (EOR) technologies. However, before nanocellulose can be applied as an EOR technique, further understanding of its transport behavior and retention in porous media is required. The research documented in this paper examines retention mechanisms that occur during nanocellulose transport. In a series of experiments, nanocellulose particles dispersed in brine were injected into sandpacks and Berea sandstone cores. The resulting retention and permeability reduction were measured. The experimental parameters that were varied include sand grain size, nanocellulose type, salinity, and flow rate. Under low salinity conditions, the dominant retention mechanism was adsorption and when salinity was increased, the dominant retention mechanism shifted towards log-jamming. Retention and permeability reduction increased as grain size decreased, which results from increased straining of nanocellulose aggregates. In addition, each type of nanocellulose was found to have significantly different transport properties. Experiments with Berea sandstone cores indicate that some pore volume was inaccessible to the nanocellulose. As a general trend, the larger the size of aggregates in bulk solution, the greater the observed retention and permeability reduction. Salinity was found to be the most important parameter affecting transport. Increased salinity caused additional aggregation, which led to increased straining and filter cake formation. Higher flow rates were found to reduce retention and permeability reduction. Increased velocity was accompanied by an increase in shear, which is believed to promote breakdown of nanocellulose aggregates. © 2018 by the authors.

  • 2.
    Aadland, Reidun
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Jakobsen, Trygve
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Long-Sanouiller, Haili
    NTNU Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Paso, Kristofer
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Torsæter, Ole
    NTNU Norwegian University of Science and Technology, Norway.
    High-temperature core flood investigation of nanocellulose as a green additive for enhanced oil recovery2019In: Nanomaterials, ISSN 2079-4991, Vol. 9, no 5, article id 665Article in journal (Refereed)
    Abstract [en]

    Recent studies have discovered a substantial viscosity increase of aqueous cellulose nanocrystal (CNC) dispersions upon heat aging at temperatures above 90 °C. This distinct change in material properties at very low concentrations in water has been proposed as an active mechanism for enhanced oil recovery (EOR), as highly viscous fluid may improve macroscopic sweep efficiencies and mitigate viscous fingering. A high-temperature (120 °C) core flood experiment was carried out with 1 wt.% CNC in low salinity brine on a 60 cm-long sandstone core outcrop initially saturated with crude oil. A flow rate corresponding to 24 h per pore volume was applied to ensure sufficient viscosification time within the porous media. The total oil recovery was 62.2%, including 1.2% oil being produced during CNC flooding. Creation of local log-jams inside the porous media appears to be the dominant mechanism for additional oil recovery during nano flooding. The permeability was reduced by 89.5% during the core flood, and a thin layer of nanocellulose film was observed at the inlet of the core plug. CNC fluid and core flood effluent was analyzed using atomic force microscopy (AFM), particle size analysis, and shear rheology. The effluent was largely unchanged after passing through the core over a time period of 24 h. After the core outcrop was rinsed, a micro computed tomography (micro-CT) was used to examine heterogeneity of the core. The core was found to be homogeneous. © 2019 by the authors.

  • 3.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Brodin, Fredrik Wernersson
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Simon, Sébastien
    Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    Oil-in-Water Emulsions Stabilized by Cellulose Nanofibrils-The Effects of Ionic Strength and pH.2019In: Nanomaterials (Basel, Switzerland), ISSN 2079-4991, Vol. 9, no 2, article id E259Article in journal (Refereed)
    Abstract [en]

    Pickering o/w emulsions prepared with 40 wt % rapeseed oil were stabilized with the use of low charged enzymatically treated cellulose nanofibrils (CNFs) and highly charged 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized CNFs. The emulsion-forming abilities and storage stability of the two qualities were tested in the presence of NaCl and acetic acid, at concentrations relevant to food applications. Food emulsions may be an important future application area for CNFs due to their availability and excellent viscosifying abilities. The emulsion characterization was carried out by visual inspection, light microscopy, viscosity measurements, dynamic light scattering and mild centrifugation, which showed that stable emulsions could be obtained for both CNF qualities in the absence of salt and acid. In addition, the enzymatically stabilized CNFs were able to stabilize emulsions in the presence of acid and NaCl, with little change in the appearance or droplet size distribution over one month of storage at room temperature. The work showed that enzymatically treated CNFs could be suitable for use in food systems where NaCl and acid are present, while the more highly charged TEMPO-CNFs might be more suited for other applications, where they can contribute to a high emulsion viscosity even at low concentrations.

  • 4.
    Aaen, Ragnhild
    et al.
    Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    Norwegian University of Science and Technology, Norway.
    Wernersson Brodin, Fredrik
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    The potential of TEMPO-oxidized cellulose nanofibrils as rheology modifiers in food systems2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 9, p. 5483-5496Article in journal (Refereed)
    Abstract [en]

    Abstract: Cellulose nanofibrils (CNFs) have been proposed for use in low-fat food products due to their availability and excellent viscosifying and gel forming abilities. As the CNFs are negatively charged, the presence of other components in foods, such as electrolytes and food additives such as xanthan gum is likely to affect their rheological properties. Hence, the study of these interactions can contribute valuable information of the suitability of CNFs as rheology modifiers and fat replacers. Rheological measurements on aqueous dispersions of TEMPO-oxidized CNFs were performed with variations in concentration of CNFs, concentration of electrolytes and with varying CNF/xanthan ratios. UV–Vis Spectroscopy was used to evaluate the onset of CNF flocculation/aggregation in the presence of electrolytes. The CNF dispersions followed a power-law dependency for viscosity and moduli on CNF concentration. Low electrolyte additions strengthened the CNF network by allowing for stronger interactions, while higher additions led to fibril aggregation, and loss of viscosity, especially under shear. The CNF/xanthan ratio, as well as the presence of electrolytes were shown to be key factors in determining whether the viscosity and storage modulus of CNF dispersions increased or decreased when xanthan was added. Graphical abstract: [Figure not available: see fulltext.].

  • 5.
    Aarstad, Olav
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Pedersen, Ina Sander
    NTNU Norwegian University of Science and Technology, Norway.
    Björnöy, Sindre H.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Mechanical properties of composite hydrogels of alginate and cellulose nanofibrils2017In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 9, no 8, article id 378Article in journal (Refereed)
    Abstract [en]

    Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering.

  • 6. Alexandrescu, L.
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Iotti, M.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gregersen, Ø.
    Belosi, F.
    Gatti, A.M.
    Air filtration of nano-particles using cellulose nanofibrils2012Conference paper (Refereed)
  • 7. Alexandrescu, L.
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gatti, A.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cytotoxicity tests of cellulose nanofibril-based structures2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20Article in journal (Refereed)
  • 8.
    Bardet, Raphael
    et al.
    Université Grenoble Alpes, France; CNRS, France.
    Reverdy, Charlène
    Université Grenoble Alpes, France; CNRS, France.
    Belgacem, Naceur
    Université Grenoble Alpes, France; CNRS, France.
    Leirset, Ingebjørg
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Bardet, Michel
    Université Grenoble Alpes, France; CEA, France.
    Bras, Julien
    Université Grenoble Alpes, France; CNRS, France.
    Substitution of nanoclay in high gas barrier films of cellulose nanofibrils with cellulose nanocrystals and thermal treatment2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 2, p. 1227-1241Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to design a nanocellulose based barrier film. For this purpose, cellulose nanofibrils (CNFs) are used as a matrix to create an entangled nanoporous network that is filled with two different nanofillers: nanoclay (reference), i.e. the mineral montmorillonite (MMT) and the bio-based TEMPO-oxidized cellulose nanocrystal (CNC-T), to produce different types of nanocelluloses and their main physical and chemical features were assessed. As expected, films based on neat CNFs exhibit good mechanical performance and excellent barrier properties at low moisture content. The introduction of 32.5 wt% of either nanofiller results in a significant improvement of barrier properties at high moisture content. Finally, thermal treatment of a dried CNF/CNC-T film results in a decrease of the oxygen permeability even at high moisture content (>70 %). This is mainly attributed to the hornification of nanocellulose. A key result of this study is that the oxygen permeability of an all-nanocellulose film in 85 % relative humidity (RH), is similar to CNF film with mineral nanoclay (MMT), i.e. 2.1 instead of 1.7 cm3 µm m−2 day−1 kPa−1, respectively.

  • 9.
    Campodoni, Elisabetta
    et al.
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Rashad, Ahmad
    University of Bergen, Norway.
    Ramírez-Rodríguez, Gloria B.
    Universidad de Granada, Spain.
    Mustafa, Kamal
    University of Bergen, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. Norwegian University of Science and Technology, Norway.
    Tampieri, Anna
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Sandri, Monica
    Institute of Science and Technology for Ceramics-National Research Council (ISTEC-CNR), Italy.
    Polymeric 3D scaffolds for tissue regeneration: Evaluation of biopolymer nanocomposite reinforced with cellulose nanofibrils2019In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 94, p. 867-878Article in journal (Refereed)
    Abstract [en]

    Biopolymers such as gelatin (Gel) and cellulose nanofibrils (CNF) have many of the essential requirements for being used as scaffolding materials in tissue regeneration; biocompatibility, surface chemistry, ability to generate homogeneous hydrogels and 3D structures with suitable pore size and interconnection, which allows cell colonization and proliferation. The purpose of this study was to investigate whether the mechanical behaviour of the Gel matrix can be improved by means of functionalization with cellulose nanofibrils and proper cross-linking treatments. Blending processes were developed to achieve a polymer nanocomposite incorporating the best features of both biopolymers: biomimicry of the Gel and structural reinforcement by the CNF. The designed 3D structures underline interconnected porosity achieved by freeze-drying process, improved mechanical properties and chemical stability that are tailored by CNF addition and different cross-linking approaches. In vitro evaluations reveal the preservation of the biocompatibility of Gel and its good interaction with cells by promoting cell colonization and proliferation. The results support the addition of cellulose nanofibrils to improve the mechanical behaviour of 3D porous structures suitable as scaffolding for tissue regeneration.

  • 10.
    Cernencu, Alexandra
    et al.
    University Politehnica of Bucharest, Romania.
    Lungu, Adriana
    University Politehnica of Bucharest, Romania.
    Stancu, Izabela
    University Politehnica of Bucharest, Romania.
    Serafim, Andrada
    University Politehnica of Bucharest, Romania.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Iovu, Horia
    University Politehnica of Bucharest, Romania; Academy of Romanian Scientists, Romania.
    Bioinspired 3D printable pectin-nanocellulose ink formulations2019In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 220, p. 12-21Article in journal (Refereed)
    Abstract [en]

    The assessment of several ink formulations for 3D printing based on two natural macromolecular compounds is presented. In the current research we have exploited the fast crosslinking potential of pectin and the remarkable shear-thinning properties of carboxylated cellulose nanofibrils, which is known to induce a desired viscoelastic behavior. Prior to 3D printing, the viscoelastic properties of the polysaccharide inks were evaluated by rheological measurements and injectability tests. The reliance of the printing parameters on the ink composition was established through one-dimensional lines printing, the base units of 3D-structures. The performance of the 3D-printed structures after ionic cross-linking was evaluated in terms of mechanical properties and rehydration behavior. MicroCT was also used to evaluate the morphology of the 3D-printed objects regarding the effect of pectin/nanocellulose ratio on the geometrical features of scaffolds. The proportionality between the two polymers proved to be the determining factor for the firmness and strength of the printed objects. © 2019

  • 11.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Kirsebom, H.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Designing nanocellulose qualities for wound dressings2013Conference paper (Refereed)
  • 12.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Powell, L.C
    Cardiff University School of Dentistry, UK; Swansea University, UK.
    Nordli, H.R
    NTNU Norwegian University of Science and Technology, Norway.
    Khan, S
    Cardiff University, UK.
    Hill, K.E
    Cardiff University, UK.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Thomas, D.W
    Cardiff University, UK.
    Nanocellulose from wood as a biomaterial for biomedical applications2014Conference paper (Refereed)
    Abstract [en]

    During the last decades major efforts have been made to produce nanocellulose from wood, where the cellulose fibres are disintegrated into individualized nanofibrils with diameters < 20 nm and lengths in the micrometre scale. Production procedures include various pre-treatments, which yield nanocelluloses with varying chemical and structural properties. One important area of research is nanocellulose as a biomaterial with potential applications within the health sector. As an example, the superior mechanical properties, good moisture retention capability and the ability to form elastic macro-porous structures are advantageous properties for utilizing nanocellulose substrates for wound dressings. However, the utilization of nanocellulose as a substrate for wound dressings requires a thorough assessment of the biocompatibility of the material.  In this respect, it has been demonstrated in-vitro that nanocellulose does not exert acute toxic phenomena on fibroblast cells. However, in addition to in-vitro cytotoxicity testing, in-vivo testing of nanocellulose and the ability of nanocellulose to resist bacterial colonization need a closer attention. This presentation will give an overview of the current research on nanocellulose as a biomaterial for wound dressing applications, considering the morphology of nanocellulose structures, mechanical properties, moisture absorption, cytotoxicity tests and nanocellulose-bacteria interactions.

  • 13.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cellulose nanofibrils: production, characterization and applications2011In: Fine Structure of Papermaking Fibres, Swedish University of Agricultural Sciences , 2011, , p. 13Chapter in book (Refereed)
  • 14.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    On the porosity and oxygen barrier properties of cellulose nanofibril-based films2011Conference paper (Refereed)
  • 15.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    On the structure and oxygen transmission rate of biodegradable cellulose nanobarriers2012In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 7Article in journal (Refereed)
  • 16.
    Chinga-Carrasco, Gary
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Pretreatment-dependent surface chemistry of wood nanocellulose for pH-sensitive hydrogels2014In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 3, no 29, p. 423-432Article in journal (Refereed)
  • 17.
    Djafari Petroudy, Seyed Rahman
    et al.
    Shahid Beheshti University, Iran.
    Ghasemian, Ali
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Resalati, Hossein
    Sari University of Agricultural Sciences and Natural Resources, Iran.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    The effect of xylan on the fibrillation efficiency of DED bleached soda bagasse pulp and on nanopaper characteristics2015In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 22, no 1, p. 385-395Article in journal (Refereed)
    Abstract [en]

    Xylan is the second most abundant polysaccharide and the most abundant hemicellulose component of soda bagasse pulp. In this study, bleached soda bagasse pulp (SB) and bleached bagasse dissolving pulp (DB) with varying amounts of xylan were fibrillated with a homogenization process. The produced fibrillated materials were used for making nanopaper structures. The surface, physical, mechanical and optical properties of the nanopaper were measured, and the effect of xylan was assessed. Laser profilometry (LP) and field emission scanning electron microscopy were applied to study the degree of the fibrillation. The pulp having the highest xylan content, SB, showed the highest yield of cellulose nanofibrils. Nanopaper produced from SB had a more consolidated structure than that produced from DB. Additionally, SB nanopaper yielded higher tensile strength, lower LP roughness, a higher barrier against oxygen and lower opacity. These results indicate a higher degree of fibrillation of the SB pulp compared to the DB pulp. Hence, the positive effect of xylan for facilitating the fibrillation of the starting pulp fibers was demonstrated.

  • 18. Djafari Petroudy, S.R.
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Ghasemain, A.
    Resalati, H.
    Gregersen, Ø.W.
    Oriented nanopaper (ONP) made of bagasse nanofibrils2012Conference paper (Refereed)
  • 19.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Temperature stability of nanocellulose dispersions2017In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 157, p. 114-121Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNF) have potential as rheology modifiers of water based fluids, e.g. drilling fluids for use in oil wells or as additives in injection water for enhanced oil recovery (EOR). The temperature in oil wells can be high (>100 °C), and the retention time long; days for drilling fluids and months for EOR fluids. Hence, it is important to assess the temperature stability over time of nanocellulose dispersions to clarify their suitability as rheology modifiers of water based fluids at such harsh conditions. Dispersions of CNF produced mechanically, by using TEMPO mediated oxidation and by using carboxymethylation as pretreatment, in addition to cellulose nanocrystals (CNC), have been subjected to heat aging. Temperature stability was best for CNC and for mechanically produced CNF that were stable after heating to 140 °C for three days. The effect of additives was evaluated; cesium formate and sodium formate increased the temperature stability of the dispersions, while there was no effect of using phosphate buffer.

  • 20.
    Heggset, Ellinor B
    et al.
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Strand, Berit L.
    NTNU Norwegian University of Science and Technology, Norway.
    Sundby, Kristin W.
    Borregaard, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Viscoelastic properties of nanocellulose based inks for 3D printing and mechanical properties of CNF/alginate biocomposite gels2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, no 1, p. 581-595Article in journal (Refereed)
    Abstract [en]

    Inks for 3D printing based on cellulose nanofibrils (CNFs) or mixtures of CNFs and either cellulose nanocrystals (CNCs) or alginate were assessed by determining their viscoelastic properties i.e. complex viscosity and storage and loss moduli (G′ and G″). Two types of alginates were used, i.e. from Laminaria hyperborea stipe and Macrocystis pyrifera. Shape fidelity of 3D printed grids were qualitatively evaluated and compared to the viscoelastic properties of the inks. The biocomposite gels containing alginate were post stabilized by crosslinking with Ca2+. Mechanical properties of the crosslinked biocomposite gels were assessed. The complex viscosity, G′ and G″ of CNF suspensions increased when the solid content was increased from 3.5 to 4.0 wt%, but levelled off by further increase in CNF solid content. The complex viscosity at low angular frequency at 4 wt% was as high as 104 Pa·s. This seemed to be the necessary viscosity level for obtaining good shape fidelity of the printed structures for the studied systems. By replacing part of the CNFs with CNCs, the complex viscosity, G′ and G″ were reduced and so was also the shape fidelity of the printed grids. The changes in complex viscosity and moduli when CNFs was replaced with alginate depended on the relative amounts of CNFs/alginate. The type of alginate (from either L. hyp. stipe or M. pyr.) did not play a role for the viscoelastic properties of the inks, nor for the printed grids before post stabilization. Replacing CNFs with up to 1.5 wt% alginate gave satisfactory shape fidelity. The effect of adding alginate and subsequent crosslinking with Ca2+, strongly affected the strength properties of the gels. By appropriate choice of relative amounts of CNFs and alginate and type of alginate, the Young’s modulus and rupture strength could be controlled within the range of 30–150 kPa and 1.5–6 kg, respectively. The deformation at rupture was around 55%. The alginate from L. hyp. stipe yields higher Young’s modulus and lower syneresis compared to M. pyr. This shows that the choice of alginate plays a significant role for the mechanical properties of the final product, although it does not influence on the viscoelastic properties of the ink. The choice of alginate should be L. hyp. stipe if high strength is desired.

  • 21. Heggset, Ellinor B
    et al.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Øyaas, Karin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Novel pretreatment pathways for dissolution of lignocellulosic biomass based on ionic liquid and low temperature alkaline treatment2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 93, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Pretreatment, fractionation and hydrolysis remains costly and challenging process steps in biochemical conversion of softwoods. Here, ionic liquid pretreatment using 1-ethyl-3-methylimidazolium acetate (EMIM-OAc) at high temperature (100 °C, 6 h) and alkali based (NaOH/urea) pretreatment at sub-zero temperature (−18 °C, 24 h) were compared and combined in studies of Norway Spruce biomass deconstruction. Both treatments significantly improved the enzymatic digestibility of the biomass. EMIM-OAc gave higher glucan than mannan digestibility, indicating a more pronounced effect on the cellulose polymer than on the hemicellulose polymer. In contrast, low temperature alkali pretreatment using NaOH or NaOH + urea gave a more pronounced effect on mannan than on glucan digestibility. By combining the two methods the total monosugar yield after enzymatic hydrolysis was improved by 20–50% as compared to using ionic liquid or alkali based pretreatment alone. Lignin dissolution was low for both methods under the conditions studied.

  • 22.
    Jakobsen, Trygve Dagsloth
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Simon, Sebastien
    NTNU Norwegian University of Science and Technology, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Paso, Kristofer
    NTNU Norwegian University of Science and Technology, Norway.
    Interactions between surfactants and cellulose nanofibrils for enhanced oil recovery2018In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, no 46, p. 15749-15758Article in journal (Refereed)
    Abstract [en]

    Chemical enhanced oil recovery (EOR) represents a series of potential solutions for extracting more oil from resources with already known locations and magnitudes. Unfortunately, many of the chemical additives in use today are not environmentally friendly. In the study a "greener" alternative for increasing viscosity of the injection water is investigated, namely cellulose nanofibrils (CNF). The nanofibrils are combined in systems with anionic sulfonate surfactants, SDBS and AOT, in order to decrease interfacial tension (IFT) between oil and water. In combination, the increase of water viscosity and decrease of IFT should result in higher ultimate oil recovery than if only conventional water flooding was applied. Interactions between cellulose nanofibrils and the surfactants have been investigated through adsorption studies, rheology, and IFT measurements. An observed synergy effect between CNF and surfactants upon viscosity of injection water, as well as with substantial decrease in IFT, leads the authors to the conclusion that an EOR system consisting of CNF and sulfonate surfactants has good potential for future applications.

  • 23.
    Kumar, Vinay
    et al.
    Åbo Akademi University, Finland.
    Ottesen, Vegar
    NTNU, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Gregersen, Öyvind Weiby
    NTNU, Norway.
    Toivakka, Martti
    Åba Akademi University, Finland.
    Coatability of cellulose nanofibril suspensions: Role of rheology and water retention2017In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 12, no 4, p. 7656-7679Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibril (CNF) suspensions are not easily coatable because of their excessively high viscosity and yield stress, even at low solids concentrations. In addition, CNF suspensions vary widely in their properties depending on the production process used, which can affect their processability. This work reports roll-to-roll coating of three different types of CNF suspensions with a slot-die, and the influence of rheology and water retention on coatability is addressed. The impact of CMC addition on the high and low shear rate rheology, water retention, coatability, and final coating quality of these suspensions is reported. All three CNF suspensions were coated successfully using the slot-die coating process. CMC addition further improved the coatability by positively influencing both the low and high shear rate viscosity and water retention of the CNF suspensions. All CNF coatings significantly improved the air, heptane vapor, grease and oil barrier, while reducing the water vapor transmission rate to some extent.

  • 24.
    Larsson, Per Tomas
    et al.
    RISE, Innventia.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Wohlert, Jakob
    KTH Royal Institute of Technology, Sweden.
    Bergenstråhle, Malin
    KTH Royal Institute of Technology, Sweden.
    Changes in the supra-molecular structure of cellulose I during TEMPO-oxidation: bringing together NMR, MD and XRD results2016In: The 7th Workshop on cellulose, regenerated cellulose and cellulose derivatives, 2016, p. 35-35, article id 9Conference paper (Other academic)
  • 25.
    Liu, Jun
    et al.
    Åbo Akademi University, Finland.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cheng, Fang
    Åbo Akademi University, Finland; University of Turku, Finland.
    Xu, Wenyang
    Åbo Akademi University, Finland.
    Willför, Stefan
    Åbo Akademi University, Finland.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Xu, Chunlin
    Åbo Akademi University, Finland.
    Hemicellulose-reinforced nanocellulose hydrogels for wound healing application2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 5, p. 3129-3143Article in journal (Refereed)
    Abstract [en]

    Polysaccharides are finding an increasing number of applications in medical and pharmaceutical fields thanks to their biodegradability, biocompatibility, and in some cases bioactivity. Two approaches were applied to use hemicelluloses as crosslinkers to tune the structural and mechanical properties of nanofibrillated cellulose (NFC) hydrogel scaffolds, and thus to investigate the effect of these properties on the cellular behavior during wound healing application. Different types of hemicellulose (galactoglucomannan (GGM), xyloglucan (XG), and xylan) were introduced into the NFC network via pre-sorption (Method I) and in situ adsorption (Method II) to reinforce the NFC hydrogels. The charge density of the NFC, the incorporated hemicellulose type and amount, and the swelling time of the hydrogels were found to affect the pore structure, the mechanical strength, and thus the cells’ growth on the composite hydrogel scaffolds. The XG showed the highest adsorption capacity on the NFC, the highest reinforcement effect, and facilitated/promoted cell growth. The pre-sorbed XG in the low-charged NFC network with a lower weight ratio (NFC/XG-90:10) showed the highest efficacy in supporting the growth and proliferation of fibroblast cells (NIH 3T3). These all-polysaccharide composite hydrogels may work as promising scaffolds in wound healing applications to provide supporting networks and to promote cells adhesion, growth, and proliferation.

  • 26. Mikczinski, M.
    et al.
    Josefsson, G.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gamstedt, E.K.
    Fatikow, S.
    Introducing an in-situ microrobotic approach for assessing the stiffness properties of microfibrillated cellulose films2012Conference paper (Refereed)
  • 27.
    Molnes, Silje N.
    et al.
    University of Stavanger, Norway; NTNU Norwegian University of Science and Technology, Norway.
    Mamonov, Aleksandr
    University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Strand, Skule
    University of Stavanger, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Investigation of a new application for cellulose nanocrystals: a study of the enhanced oil recovery potential by use of a green additive2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 4, p. 2289-2301Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNC) were investigated for use in a potential new application, enhanced oil recovery. Core flooding experiments were performed on outcrop sandstone cores using CNC particles dispersed in low salinity brine (CNC-LS). Core flooding experiments performed on fully water-saturated cores confirm that a majority of viscosity-generating CNC particles successfully traverse the cores at temperature conditions ranging from 60 to 120 A degrees C. Oil recovery tests performed on crude oil saturated sandstone cores at 60 and 90 A degrees C show that when CNC-LS is applied in tertiary mode, ultimate oil recovery increases. During tertiary CNC-LS injection, CNC particles exacerbate differential pressure fluctuations, a phenomenon attributable to log jamming in pore throats, causing remobilisation of oil trapped within pore space regions. Results from the current work indicate that CNC particles dispersed in low saline brine remain promising for implementation in enhanced oil recovery operations.

  • 28.
    Molnes, Silje N.
    et al.
    NTNU Norwegian University of Science and Technology, Norway; University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Strand, Skule
    University of Stavanger, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    The effects of pH, time and temperature on the stability and viscosity of cellulose nanocrystal (CNC) dispersions: implications for use in enhanced oil recovery2017In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 24, no 10, p. 4479-4491Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals (CNC) are currently being investigated as potential additives for enhanced oil recovery (EOR). Presented in this paper is a study investigating the effects of different physical and chemical environments that low concentration CNC dispersions may be subjected to at oil reservoir conditions. Different concentrations of CNC dispersed in de-ionized water and in a 1000 ppm NaCl brine were subjected to variations in pH and temperature, and the results showed that the dispersions remained stable in the pH range expected in oil reservoirs (between 5 and 9). Stable dispersions were also observed when heated to temperatures ranging from 50 to 90 °C. At extended heat aging at 90 and 120 °C for seven days; beginning degradation was observed for both types of CNC dispersions; with viscosity increase and pH decrease as the most important indicators. CNC dispersed in 1000 ppm NaCl brine was generally more heat tolerant than the CNC dispersed in de-ionized water. The increase in viscosity during heat aging can be very interesting for EOR applications. A fluid that increases its viscosity with heat and time will be easier to inject due to a low initial viscosity, and when the viscosity increases in the porous reservoir, the effect can be a stable waterfront and less viscous fingering, which again can lead to increased sweep efficiency and better oil recovery.

  • 29.
    Molnes, Silje N.
    et al.
    UoS University of Stavanger, Norway; NTNU Norwegian University of Science and Technology, Norway.
    Torrijos, Ivan P.
    UoS University of Stavanger, Norway.
    Strand, Skule
    UoS University of Stavanger, Norway.
    Paso, Kristofer G.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Sandstone injectivity and salt stability of cellulose nanocrystals (CNC) dispersions: Premises for use of CNC in enhanced oil recovery2016In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 93, p. 152-160Article in journal (Refereed)
    Abstract [en]

    Reservoir production is frequently supported by using flooding fluids, often seawater. The efficiency is affected by various factors, such as the wettability of the reservoir rock and the mobility ratio between reservoir oil and injected fluid phase. These factors again influence sweep efficiency, which is the fraction of the total reservoir oil volume in contact with injected fluid during oil recovery. Addition of nanoparticles can affect the sweep efficiency on a macroscopic level by increasing the volume of petroleum in contact with the flooding fluid. Presented here are core-flooding studies performed using cellulose nanocrystals (CNC) of different concentrations in low-saline water. The studies were performed to investigate the injectivity of CNC into a high-permeable sandstone core, and to observe the effects addition of electrolytes had on the rheological properties of a low concentration dispersion of CNC. Zeta- potential and shear viscosity of dilute dispersions containing CNC was investigated under increasing electrolyte concentration. The flooding experiments show that the CNC has good injectivity in sandstone for all concentrations used, and the viscosity measurements performed on the effluent prove that the particles are able to travel through the core. Being sufficiently small for injection into sandstone and showing good colloidal stability at low salinities, CNC particles have the premises necessary to function properly as a flooding additive for enhanced oil recovery (EOR) in sandstone reservoirs.

  • 30.
    Ojansivu, Miina
    et al.
    Tampere University, Finland.
    Rashad, Ahmad
    University of Bergen, Norway.
    Ahlinder, Astrid Elisabet
    KTH Royal institute of technology, Sweden.
    Massera, Jonathan
    Tampere University, Finland.
    Mishra, Ayush
    Tampere University, Finland.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Finne-Wistrand, Anna
    KTH Royal institute of technology, Sweden.
    Miettinen, Susanna
    Tampere University, Finland.
    Mustafa, Kamal
    University of Bergen, Norway.
    Wood-based nanocellulose and bioactive glass modified gelatin-alginate bioinks for 3D bioprinting of bone cells2019In: Biofabrication, ISSN 1758-5082, E-ISSN 1758-5090, Vol. 11, no 3Article in journal (Refereed)
    Abstract [en]

    A challenge in the extrusion-based bioprinting is to find a bioink with optimal biological and physicochemical properties. The aim of this study was to evaluate the influence of wood-based cellulose nanofibrils (CNF) and bioactive glass on the rheological properties of gelatin-alginate bioinks and the initial responses of bone cells embedded in these inks. CNF modulated the flow behavior of the hydrogels, thus improving their printability. Chemical characterization by SEM-EDX and ion release analysis confirmed the reactivity of the BaG in the hydrogels. The cytocompatibility of the hydrogels was shown to be good, as evidenced by the viability of human osteoblast-like cells (Saos-2) in cast hydrogels. For bioprinting, 4-layer structures were printed from cell-containing gels and crosslinked with CaCl2. Viability, proliferation and alkaline phosphatase activity (ALP) were monitored over 14 days. In the BaG-free gels, Saos-2 cells remained viable, but in the presence of BaG the viability and proliferation decreased in correlation with the increased viscosity. Still, there was a constant increase in the ALP activity in all the hydrogels. Further bioprinting experiments were conducted using human bone marrow-derived mesenchymal stem cells (hBMSCs), a clinically relevant cell type. Interestingly, hBMSCs tolerated the printing process better than Saos-2 cells and the ALP indicated BaG-stimulated early osteogenic commitment. The addition of CNF and BaG to gelatin-alginate bioinks hold great potential for bone tissue engineering applications.

  • 31.
    Ottesen, V
    et al.
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering.
    Gregersen,  Ø
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering;.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Nanocellulose in Paper and Packaging2014Conference paper (Refereed)
    Abstract [en]

    One possible way to improve competitiveness of paper materials is through utilization of nanocellulose to achieve new properties or to reduce production cost. Several studies have shown that nanofibrillar cellulose (NFC) can act as strength enhancing additive in paper or for paper surface improvements. NFC has the potential to bind large amounts of inorganic fillers in the paper sheet, and by this reduce energy consumption during paper production considerably. However, there are challenges that need to be addressed before the novel concepts can be realized, e.g. impaired drainage and drying of paper resulting from addition of NFC. This may be solved by obtaining the right balance between NFC quality, chemicals and additives. Promising results in this respect have been obtained  but this is still in an early stage. Fiber-based packaging materials represent a “green” alternative to petroleum based packaging solutions. Depending on the packaging category, different properties are important. For the segment liquid packaging board, barrier against oxygen is important. Currently, this is obtained by using aluminum, or the petroleum-based polymer EVOH in combination with a water barrier. Replacing these materials with “green” alternatives would represent a large environmental achievement. While superior oxygen barrier properties has been demonstrated for NFC,  good barrier against water and oxygen requires the combination of nanofibrils with complementary materials. Adequate combinations with other materials and feasible application techniques are still challenges that need to be solved. Other packaging segments require other properties, e.g. high stiffness or fracture toughness. By development of appropriate nanocellulose qualities, such properties can be improved. By preparing fibrils with small diameter, translucent films can be prepared. This is an interesting property for food packaging, where transparency may be a desired trait.

  • 32.
    Ottesen, V
    et al.
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering.
    Gregersen,  Ø
    Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering;.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Nanocellulose Properties of Interest for Paper and Packaging2014Conference paper (Refereed)
    Abstract [en]

    Cellulose Nano-Fibrils (CNF) is a biocompatible nano-material with appealing mechanical and optical properties. The high specific surface area (SSA) of nanofibrils ensure that a large fraction of the polymer chains in each fibril are surface fibrils, meaning numerous surface hydroxyl groups will be available to form bonds between components in the paper, ensuring high density and strength. CNF may be added to conventional paper as a strengthening agent. CNF films may be used as a barrier coating, or CNF sheets may be used in a number of products due to their potential transparency, strength and barrier properties. As a paper additive, CNF as a nanomaterial acts as a material that increases density and form bonds between fibers in the paper, providing an increased strength and stiffness whereas dusting and permeability is reduced. For papers where strength is chiefly limited by inter-fiber bonding strength, increases in excess of 100 % may be achieved by addition of small amounts of CNF. Less, but still significant contributions can be seen for papers whose strength is less dependent on inter-fiber bonding strength. Due to the pore-blocking properties of CNF coupled with Cellulose’s hydrophilic properties, dewatering on the paper machine is a challenge when CNF is used in this fashion. The high density, viz. the low porosity and small pore size (~0.47 nm), of CNF films provide a significant reduction in mass-transport. Applying such a film to a less efficient barrier material, or producing a pure CNF film presents oxygen transfer rates comparable with the best synthetic polymer films produced for this purpose. Sheets of pure CNF or a CNF composite may transmit 90 % of incident light with a wavelength of 600 nm. This transparency is due to the high density and small fibril size in sheets of pure CNF or a CNF-based composite, which results in a lower scattering coefficient compared to corresponding conventional fiber based sheets. Transparent sheets such as these may be of interest in packaging applications where the packaged goods, such as foodstuffs or luxury articles, is desired displayed to the end customer. The properties of CNF, whether as a film, a paper additive or a major paper or composite component may be of significant industrial interest due to the unique properties of the material.

  • 33.
    Ottesen, Vegar
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Kumar, Vinay Santhosh
    Åbo Akademi University, Finland.
    Toivakka, Martti
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Chinga-Carrasco, Gary
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Weiby Gregersen, Öyvind
    NTNU Norwegian University of Science and Technology, Norway.
    Viability and properties of roll-to-roll coating of cellulose nanofibrils on recycled paperboard2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 2, p. 179-188Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNF) are, due in large part to excellent gas barrier properties, a potential environmentally friendly alternative to inorganic and petrochemical coatings of e.g. paperboard in packaging applications. In the current paper successful roll-to-roll coating of three qualities of CNF is demonstrated on a recycled quality, porous paperboard using a custom-built pilot machine. Single layers of three different thicknesses were applied for each coating. The three CNF qualities used were carboxymethylated CNF (CNF-C), TEMPOoxidized CNF (CNF-T) and mechanically produced CNF without chemical pre-treatment (CNF-M). All three qualities, which have a range of surface charge, fibril size and fibril size distribution, are shown to produce films that adhere well to the base board. It is revealed that the coating is suspended across surface pores in the base board, as opposed to penetrate into the base board pore structure. Samples were investigated for air and water permeability, gloss, surface roughness and hole density in the coating. Chemically pretreated qualities outperform CNF-M. Addition of 5 wt% carboxy-methyl cellulose (CMC) was shown to reduce hole formation, improve gloss and reduce surface roughness. For thick applications of pre-treated CNF, in particular CNF-C, mechanical strength of the board in and out of the plane increase beyond the un-treated or water treated base board. Possibly a consequence of matter migrating through the base board from the CNF suspension.

  • 34.
    Ottesen, Vegar
    et al.
    NTNU, Norway.
    Larsson, Per Tomas
    KTH Royal Institute of Technology,´Sweden.
    Chinga-Carrasco, Gary
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU, Norway.
    Gregersen, Öyvind
    NTNU, Norway.
    Mechanical properties of cellulose nanofibril films: effects of crystallinity and its modification by treatment with liquid anhydrous ammonia2019In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 26, no 11, p. 6615-27Article in journal (Refereed)
    Abstract [en]

    The influence of cellulose crystallinity on mechanical properties of cellulose nano-fibrils (CNF) was investigated. Degree of crystallinity (DoC) was modified using liquid anhydrous ammonia. Such treatment changes crystal allomorph from cellulose I to cellulose III, a change which was reversed by subsequent boiling in water. DoC was measured using solid state nuclear magnetic resonance (NMR). Crystalline index (CI) was also measured using wide angle X-ray scattering (WAXS). Cotton linters were used as the raw material. The cotton linter was ammonia treated prior to fibrillation. Reduced DoC is seen to associate with an increased yield point and decreased Young modulus. Young modulus is here defined as the maximal slope of the stress–strain curves. The association between DoC and Young modulus or DoC and yield point are both statistically significant. We cannot conclude there has been an effect on strainability. While mechanical properties were affected, we found no indication that ammonia treatment affected degree of fibrillation. CNF was also studied in air and liquid using atomic force microscopy (AFM). Swelling of the nanofibers was observed, with a mean diameter increase of 48.9%.

  • 35.
    Ottesen, Vegar
    et al.
    NTNU Norwegian university of science and technology, Norway.
    Roede, Erik Dobloug
    NTNU Norwegian university of science and technology, Norway.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian university of science and technology, Norway.
    Gregersen, Øyvind Weiby
    NTNU Norwegian university of science and technology, Norway.
    Focused ion beam tomography as a means for characterization of CNF in a paper matrix2017In: 16th Fundamental Research symposium, 2017, p. 595-609Conference paper (Refereed)
  • 36.
    Ottesen, Vegar
    et al.
    NTNU Norwegian University of Science and Technology, Norway.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute. NTNU Norwegian University of Science and Technology, Norway.
    Gregersen, Øyvind W.
    NTNU Norwegian University of Science and Technology, Norway.
    Mixing of cellulose nanofibrils and individual furnish components: Effects on paper properties and structure2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 3, p. 441-447Article in journal (Refereed)
    Abstract [en]

    Thermo-mechanical pulp (TMP) handsheets with different fractions of cellulose nano fibrils (CNF) and ground calcium carbonate (GCC) were made. CNF and retention chemicals were added in three different ways; to GCC, to long fibre fraction (LFF) or to complete furnish. The different addition strategies affected dewatering time, tensile strength and permeability, however opacity was not affected. Depending on filler and CNF levels, adding CNF to GCC produced the most beneficial effects on paper properties; CNF had a lower impact on dewatering times and permeability and GCC reduced strength less than for competing strategies. Adding CNF to LFF produced the least beneficial results using the same metrics. Scanning electron microscopy (SEM) analysis of the sheets reveal that sheets produced using the different strategies are structurally different; adding CNF and retention chemicals to GCC appears to have increased GCC clustering, whereas adding CNF and retention chemicals to LFF appears to have increased the fraction of GCC adsorbed on the fiber walls. CNF and retention chemical addition to complete furnish showed GCC clustering and adhering to the fiber walls, of which clustering appeared the most common.

  • 37.
    Petroudy, S.R.D
    et al.
    NTNU Norwegian University of Science and Technology, Norway; Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Ghasemain, A
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Resalati, H
    Gorgan University of Agricultural Sciences and Natural Resources, Iran.
    Effects of bagasse microfibrillated cellulose and cationic polyacrylamide on key properties of bagasse paper2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 99, p. 311-318Article in journal (Refereed)
  • 38.
    Rashad, Ahmad
    et al.
    University of Bergen, Norway.
    Mohamed-Ahmed, Samih
    University of Bergen, Norway.
    Ojansivu, Miina
    University of Bergen, Norway; University of Tampere, Finland.
    Berstad, Kaia
    University of Bergen, Norway.
    Yassin, Mohammad
    University of Bergen, Norway.
    Kivijärvi, Tove
    KTH Royal Institute of Technology, Sweden.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Coating 3D Printed Polycaprolactone Scaffolds with Nanocellulose Promotes Growth and Differentiation of Mesenchymal Stem Cells2018In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, no 11, p. 4307-4319Article in journal (Refereed)
    Abstract [en]

    3D printed polycaprolactone (PCL) has potential as a scaffold for bone tissue engineering, but the hydrophobic surface may hinder optimal cell responses. The surface properties can be improved by coating the scaffold with cellulose nanofibrils material (CNF), a multiscale hydrophilic biocompatible biomaterial derived from wood. In this study, human bone marrow-derived mesenchymal stem cells were cultured on tissue culture plates (TCP) and 3D printed PCL scaffolds coated with CNF. Cellular responses to the surfaces (viability, attachment, proliferation, and osteogenic differentiation) were documented. CNF significantly enhanced the hydrophilic properties of PCL scaffolds and promoted protein adsorption. Live/dead staining and lactate dehydrogenase release assays confirmed that CNF did not inhibit cellular viability. The CNF between the 3D printed PCL strands and pores acted as a hydrophilic barrier, enhancing cell seeding efficiency, and proliferation. CNF supported the formation of a well-organized actin cytoskeleton and cellular production of vinculin protein on the surfaces of TCP and PCL scaffolds. Moreover, CNF-coated surfaces enhanced not only alkaline phosphatase activity, but also collagen Type-I and mineral formation. It is concluded that CNF coating enhances cell attachment, proliferation, and osteogenic differentiation and has the potential to improve the performance of 3D printed PCL scaffolds for bone tissue engineering.

  • 39.
    Rashad, Ahmad
    et al.
    University of Bergen, Norway.
    Suliman, Salwa
    University of Bergen, Norway.
    Mustafa, Manal
    Oral Health Centre of Expertise in Western Norway, Norway.
    Pedersen, Torbjörn
    University of Bergen, Norway.
    Campodoni, Elisabetta
    National Research Council of Italy, Italy.
    Sandri, Monica
    National Research Council of Italy, Italy.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Inflammatory responses and tissue reactions to wood-Based nanocellulose scaffolds2019In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 97, p. 208-221Article in journal (Refereed)
    Abstract [en]

    Two wood-derived cellulose nanofibril (CNF) porous scaffolds were prepared by TEMPO-oxidation and carboxymethylation. The effects of these scaffolds on the production of inflammatory cytokines by human macrophage-like cells (U937) was profiled in vitro after 1 and 3 days and in subcutaneous tissues of rats after 4 and 30 days, using PCR and Multiplex arrays. Tissue culture plates (TCP) and gelatin scaffolds served as controls in vitro and in vivo respectively. After 3 days in vitro, there was no significant difference between the effects of CNF scaffolds and TCP on the production of chemokines/growth factors and pro-inflammatory cytokines. At day 4 in vivo there was significantly higher gene expression of the anti-inflammatory IL-1Ra in the CNF scaffolds than the gelatin scaffold. Production of IL-1β, IL-6, MCP-1, MIP-1α CXCL-1 and M-CSF was significantly less than in the gelatin, demonstrating an early mild inflammatory response. At day 30, both CNF scaffolds significantly stimulated the production of the anti-inflammatory cytokine IL-10. Unlike gelatin, neither CNF scaffold had degraded 180 days post-implantation. The slow degradation of CNF scaffolds resulted in a foreign body reaction, with high production of IL-1β, IL-2, TNF-α, IFN-ϒ, MCP-1, MIP-1α, M-CSF, VEGF cytokines and expression of MMP-9 gene. The surface chemistry of the CNF scaffolds elicited a modest effect on cytokine production and did not shift the inflammatory profile in vitro or in vivo. The decisive role in development of the foreign body reaction was the slow degradation of the CNF scaffolds.

  • 40.
    Rashad, Amad
    et al.
    University of Bergen, Norway.
    Mustafa, Kamal
    University of Bergen, Norway.
    Heggset, Ellinor B
    RISE - Research Institutes of Sweden, Bioeconomy, PFI.
    Syverud, Kristin
    RISE - Research Institutes of Sweden, Bioeconomy, PFI. NTNU Norwegian University of Science and Technology, Norway.
    Cytocompatibility of Wood-Derived Cellulose Nanofibril Hydrogels with Different Surface Chemistry2017In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 18, no 4, p. 1238-1248Article in journal (Refereed)
    Abstract [en]

    The current study aims to demonstrate the influence of the surface chemistry of wood-derived cellulose nanofibril (CNF) hydrogels on fibroblasts for tissue engineering applications. TEMPO-mediated oxidation or carboxymethylation pretreatments were employed to produce hydrogels with different surface chemistry. This study demonstrates the following: first, the gelation of CNF with cell culture medium and formation of stable hydrogels with improved rheological properties; second, the response of mouse fibroblasts cultured on the surface of the hydrogels or sandwiched within the materials with respect to cytotoxicity, cell attachment, proliferation, morphology, and migration. Indirect cytotoxicity tests showed no toxic effect of either hydrogel. The direct contact with the carboxymethylated hydrogel adversely influenced the morphology of the cells and limited their spreading, while typical morphology and spreading of cells were observed with the TEMPO-oxidized hydrogel. The porous fibrous structure may be a key to cell proliferation and migration in the hydrogels.

  • 41.
    Rees, A
    et al.
    Swansea University WCPC.
    Powell, L.C
    Centre for NanoHealth, College of Engineering, Swansea University, Swansea, UK.; Tissue Engineering and Reparative Dentistry, Cardiff University School of Dentistry, Cardiff, UK..
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gethin, D.T
    Swansea University WCPC.
    Claypole, T.C
    Swansea University WCPC.
    Deganello, D
    Swansea University WCPC.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Studies on the 3D Printing of Nanocellulose Structures2014Conference paper (Refereed)
    Abstract [en]

    Nanocellulose has a variety of advantages, which make the material most suitable for use in biomedical devices such as wound dressings. The material is strong, can be used for producing transparent films, can keep a moist environment and form elastic gels with bio-responsive characteristics. In this study we explore the application of nanocellulose as a bioink for use in a bioprinting process. Two different nanocelluloses were used, prepared with TEMPO mediated oxidation and a combination of carboxymethylation and periodate oxidation. The combination of carboxymethylation and periodate oxidation produced a homogeneous material with short nanofibrils. The small dimensions of the nanofibrils reduced the viscosity of the nanocellulose thus yielding a material with good rheological properties for use as a bioink. We also demonstrated that both nanocelluloses inhibited bacterial growth, which is an interesting property of these novel materials.

  • 42.
    Rees, Adam
    et al.
    Swansea University, UK.
    Powell, Lydia C.
    Swansea University, UK; Cardiff University, UK.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Gethin, David T.
    Swansea University, UK.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Hill, Katja E.
    Cardiff University, UK.
    Thomas, David W.
    Cardiff University, UK.
    3D bioprinting of carboxymethylated-periodate oxidized nanocellulose constructs for wound dressing applications2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, Vol. 2015, article id 925757Article in journal (Refereed)
    Abstract [en]

    Nanocellulose has a variety of advantages, which make the material most suitable for use in biomedical devices such as wound dressings. The material is strong, allows for production of transparent films, provides a moist wound healing environment, and can form elastic gels with bioresponsive characteristics. In this study, we explore the application of nanocellulose as a bioink for modifying film surfaces by a bioprinting process. Two different nanocelluloses were used, prepared with TEMPO mediated oxidation and a combination of carboxymethylation and periodate oxidation. The combination of carboxymethylation and periodate oxidation produced a homogeneous material with short nanofibrils, having widths <20 nm and lengths <200 nm. The small dimensions of the nanofibrils reduced the viscosity of the nanocellulose, thus yielding a material with good rheological properties for use as a bioink. The nanocellulose bioink was thus used for printing 3D porous structures, which is exemplified in this study. We also demonstrated that both nanocelluloses did not support bacterial growth, which is an interesting property of these novel materials.

  • 43.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Controlling the elastic modulus of cellulose nanofibrils hydrogels by crosslinking: a premise for their use in medical applications2014Conference paper (Refereed)
    Abstract [en]

    Cellulose nanofibrils can be utilized as a building block in novel material concepts. One area of particular interest is formation of hydrogels for use in medical applications such as drug delivery and tissue engineering. Compared to bacterial cellulose, which is presently used for some medical applications but is produced through a somewhat inefficient process, cellulose nanofibrils from wood can be produced effectively and in large quantities. Cellulose nanofibrils are nano-scaled fibres with high aspect ratio and strong interactions with water. In order to produce stable macroscopic structures which perform adequately in humid conditions, the nanofibrils must be cross-linked in a controlled way. Several properties are important for a successful utilization of hydrogels for biomedical applications, such as degradation, bio-adhesion, bioactivity, transport through the network and mechanical properties. In the present work focus is set on the mechanical and viscoelastic properties of hydrogels. Hydrogels of oxidized cellulose nanofibrils were formed by crosslinking the nanofibrils through the formation of covalent bonds between the crosslinking molecules and oxidized sites at the nanofibril surfaces. The elastic moduli of the hydrogels were controlled by varying the concentration and the length of the crosslinking molecules. Results from cytotoxicity studies of cellulose nanofibrils will be shown.

  • 44.
    Syverud, Kristin
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Nanocellulose: a promising green flooding additive2014Conference paper (Refereed)
  • 45.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Alexandrescu, L.
    Gatti, A.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Biocompatibility studies of nanofibril structures based on Eucalyptus and Pinus radiata pulp fibres2012Conference paper (Refereed)
  • 46.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Alexandrescu, L.
    Gatti, A.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Belosi, F.
    Verifying the biocompatibility of cellulose nanofibril structures as a first step to develop filters for air-borne nanoparticles2013Conference paper (Refereed)
  • 47.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Alexandrescu, L.
    Manti, Canonico
    Gatti, A.
    Physical, chemical and biological characterization of a new nanostructured filtering membrane2012Conference paper (Refereed)
  • 48.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Salvatori, R.
    Gatti, A.
    Towards novel filter concepts for nanopollution2011Conference paper (Refereed)
  • 49.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Toledo, J.
    Toledo, P.G.
    A comparative study of Eucalyptus and Pinus Radiata pulp fibres as raw materials for production of cellulose nanofibrils2011In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 84Article in journal (Refereed)
  • 50.
    Syverud, Kristin
    et al.
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Kirsebom, H.
    Hajizadet, S.
    Chinga-Carrasco, Gary
    RISE, Innventia, PFI – Paper and Fiber Research Institute.
    Cross-linking cellulose nanofibrils for potential elastic cryo-structured gels2011In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 6Article in journal (Refereed)
12 1 - 50 of 59
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