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  • 1.
    Carrick, Christopher
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Brismar, Hjalmar
    KTH, School of Engineering Sciences (SCI), Applied Physics, Cell Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aidun, Cyrus
    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.
    Native and functionalized micrometre-sized cellulose capsules prepared by microfluidic flow focusing2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 37, p. 19061-19067Article in journal (Refereed)
    Abstract [en]

    Cellulose capsules with average outer and inner radii of approximately 44 mu m and 29 mm respectively were prepared from cellulose dissolved in a mixture of lithium chloride and dimethylacetamide using a microfluidic flow focusing device (MFFD). The MFFD had three inlets where octane oil in a cellulose solution in silicone oil was used to produce a double emulsion containing a cellulose capsule. This technique enables the formation of capsules with a narrow size distribution which can be beneficial for drug delivery or controlled release capsules. In this respect, cellulose is a highly interesting material since it is known to cause no autoimmune reactions when used in contact with human tissue. Furthermore, by controlling the chemical properties of the cellulose, it is possible to trigger a swelling of the capsules and consequentially the release of an encapsulated substance, e. g. a model drug, when the capsule becomes exposed to an external stimulus. To demonstrate this, capsules were functionalized by carboxymethylation to be pH- responsive and to expand approximately 10% when subjected to a change in pH from 3 to 10. The diffusion constant of a model drug, a 4 kDa fluorescently labelled dextran, through the native capsule wall was estimated to be 6.5 X 10(-14) m(2) s(-1) by fitting fluorescence intensity data to Fick's second law.

  • 2.
    Carrick, Christopher
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Immunoselective cellulose nanospheres: a versatile platform for nanotheranostics2014In: ACS Macro Letters, E-ISSN 2161-1653, Vol. 3, no 11, p. 1117-1120Article in journal (Refereed)
    Abstract [en]

    This paper describes a novel route for the preparation and functionalization of perfectly spherical cellulose nanospheres (CNSs), ranging from 100 to 400 nrn with a typical diameter of 160-170 nrn,for use in theranostics. The method of preparation enables both surface and interior bulk functionalization, and this presumably also makes the CNSs suitable for use in end-use applications other than theranostics. Surface functionalization was here demonstrated by antibody conjugation with an antibody specific toward the epidermal growth factor receptor (EGFR) protein, i.e., facilitating interaction with cancer cells having the EGFR. Besides showing specificity, the CNS-antibody conjugates showed a very low nonspecific binding. The CNSs could easily be bulk functionalized by embedding gold nanoparticles in the cellulose sphere matrix during CNS preparation to provide imaging contrast for diagnostic purposes.

  • 3.
    Carrick, Christopher
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Immunoselective cellulose nanospheres by antibody conjugation2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 727-COLL-Article in journal (Other academic)
  • 4.
    Cervin, Nicholas Tchang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Johanson, Erik
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Strong, Water-Durable, and Wet-Resilient Cellulose Nanofibril-Stabilized Foams from Oven Drying2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 18, p. 11682-11689Article in journal (Refereed)
    Abstract [en]

    Porous materials from cellulose nanofibrils (CNFs) have been prepared using Pickering foams from aqueous dispersions. Stable wet foams were first produced using surface-modified CNFs as stabilizing particles. To better maintain the homogeneous pore structure of the foam after drying, the foams were dried in an oven on a liquid-filled porous ceramic frit. The cell structure was studied by scanning electron microscopy and liquid porosimetry, the mechanical properties were studied by compression testing, and the liquid absorption capacity was determined both with liquid porosimetry and by soaking in water. By controlling the charge density of the CNFs, it was possible to prepare dry foams with different densities, the lowest density being 6 kg m(-3), that is, a porosity of 99.6%. For a foam with a density of 200 kg m(-3) the compressive Young's modulus was 50 MPa and the energy absorption to 70% strain was 2.3 MJ M-3. The use of chemically modified CNFs made it possible to prepare cross-linked foams with water-durable and wet-resilient properties. These foams absorbed liquid up to 34 times their own weight and were able to release this liquid under compression and to reabsorb the same amount when the pressure was released.

  • 5.
    Ciftci, Goksu Cinar
    et al.
    KTH Royal Inst Technol, Fibre & Polymer Technol, Stockholm, Sweden..
    Larsson, Per
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Riazanova, Anastasia V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Karppinen, Anni
    Borregaard AS, Sarpsborg, Norway..
    Ovrebo, Hans Henrik
    Borregaard AS, Sarpsborg, Norway..
    Berglund, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Influence of microfibrillated cellulose fractions on the rheology of water suspensions: Colloidal interactions and viscoelastic properties2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Article in journal (Other academic)
  • 6.
    Erlandsson, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Duran, Veronica Lopez
    Granberg, Hjalmar
    Innventia AB.
    Sandberg, Mats
    Acreo Swedish ICT AB.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Macro- and mesoporous nanocellulose beads for use in energy storage devices2016In: APPLIED MATERIALS TODAY, ISSN 2352-9407, Vol. 5, p. 246-254Article in journal (Refereed)
    Abstract [en]

    Chemically cross-linked, wet-stable cellulose nanofibril (CNF) aerogel beads were fabricated using a novel procedure. The procedure facilitated controlled production of millimetre-sized CNF aerogel beads without freeze-drying or critical point drying, while still retaining a highly porous structure with low density. The aerogel beads were mechanically robust in the dry state, supporting loads of 1.3 N at 70% compression, even after being soaked in water and re-dried. Furthermore, they displayed both a good stability in water and a remarkably good shape recovery after wet compression. Owing to the stability in water, the entire surface of the highly porous aerogel beads could be successfully functionalized with polyelectrolytes and carboxyl-functionalized single-wall carbon nanotubes (CF-SWCNTs) using the Layer-by-Layer technique, introducing a significant electrical conductivity (1.6 mS/cm) to the aerogel beads. The functionalized, electrically conducting aerogel beads could carry as much as 2 kA/cm(2) and act as electrodes in a supercapacitor displaying a stabilized charge storage capacity of 9.8 F/g after 50 charging-discharging cycles.

  • 7.
    Gustafsson, Emil
    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.
    Hedberg, Jonas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Larsson, Per A.
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Vibrational sum frequency spectroscopy on polyelectrolyte multilayers: Effect of molecular surface structure on macroscopic wetting properties2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 15, p. 4435-4442Article in journal (Refereed)
    Abstract [en]

    Adsorption of a single layer of molecules on a surface, or even a reorientation of already present molecules, can significantly affect the surface properties of a material. In this study, vibrational sum frequency spectroscopy (VSFS) has been used to study the change in molecular structure at the solid-air interface following thermal curing of polyelectrolyte multilayers of poly(allylamine hydrochloride) and poly(acrylic acid). Significant changes in the VSF spectra were observed after curing. These changes were accompanied by a distinct increase in the static water contact angle, showing how the properties of the layer-by-layer molecular structure are controlled not just by the polyelectrolyte in the outermost layer but ultimately by the orientation of the chemical constituents in the outermost layers.

  • 8.
    Gustafsson, Emil
    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.
    Hedberg, Jonas
    Larsson, Per A.
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Johnson, C. Magnus
    Vibrational sum frequency spectroscopy on polyelectrolyte multilayers: modelling of hydrophobic fibresManuscript (preprint) (Other academic)
  • 9.
    Gustafsson, Emil
    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.
    Larsson, Per A.
    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. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Treatment of cellulose fibres with polyelectrolytes and wax colloids to create tailored highly hydrophobic fibrous networks2012In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 414, p. 415-421Article in journal (Refereed)
    Abstract [en]

    Paper is a versatile material with obvious advantages in being both inexpensive and environment friendly. However, a major drawback compared with many other materials, such as plastics, is that it is sensitive to both liquid water and moist air. Traditionally paper is protected from liquid water by sizing. The present work presents a new way to make paper water resistant by combining the layer-by-layer (LbL) technique with the adsorption of a colloidal wax onto the multilayer structure. After the adsorption of five layers of poly(allylamine hydrochloride) and poly(acrylic acid) followed by the adsorption of 8. mg paraffin wax per gram fibre, the contact angle measured 60. s after a drop of water was applied to the sheet was about 138°. If the sheets were cured for 30. min at 160. °C after sheet making, the contact angle was ca. 150°. The heat treatment of sheets prepared from LbL-modified fibres without the addition of wax gave a contact angle of about 113°. To decouple structural effects from changes in surface energy upon heat treatment of PAH/PAA LbL films, model experiments were carried out where LbL assemblies were prepared on silicon oxide and cellulose model surfaces. The contact angle increased when these films were heat treated but it did not exceed 90°. The reason for this is due to the lack of structure of the model surfaces on a micrometre scale. The adsorption of wax impaired the mechanical properties of paper sheets made from modified fibres compared to sheets from the LbL-modified fibres. However, at an adsorption of 8. mg paraffin wax per gram fibre there was still an increase by 37 ± 1% in tensile strength index compared to the untreated reference pulp (33.8 ± 0.7 and 24.7 ± 0.6. kNm/kg respectively).

  • 10.
    Henschen, Jonatan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Illergård, Josefin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Contact-active antibacterial aerogels from cellulose nanofibrils2016In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 146, p. 415-422Article in journal (Refereed)
    Abstract [en]

    The use of cellulose aerogels as antibacterial materials has been investigated by applying a contact-active layer-by-layer modification to the aerogel surface. Studying the adsorption of multilayers of polyvinylamine (PVAm) and polyacrylic acid to aerogels comprising crosslinked cellulose nanofibrils and monitoring the subsequent bacterial adhesion revealed that up to 26 mg PVAm g aerogel−1 was adsorbed without noticeably affecting the aerogel structure. The antibacterial effect was tested by measuring the reduction of viable bacteria in solution when the aerogels were present. The results show that >99.9% of the bacteria adhered to the surface of the aerogels. Microscopy further showed adherence of bacteria to the surfaces of the modified aerogels. These results indicate that it is possible to create materials with three-dimensional cellulose structures that adsorb bacteria with very high efficiency utilizing the high specific surface area of the aerogels in combination with their open structure.

  • 11.
    Henschen, Jonatan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Illergård, Josefin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bacterial adhesion to polyvinylamine-modified nanocellulose films2017In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, E-ISSN 1873-4367, Vol. 151, p. 224-231Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibril (CNF) materials have been widely studied in recent years and are suggested for a wide range of applications, e.g., medical and hygiene products. One property not very well studied is the interaction between bacteria and these materials and how this can be controlled. The current work studies how bacteria adhere to different CNF materials modified with polyelectrolyte multilayers. The tested materials were TEMPO-oxidized to have different surface charges, periodate-oxidized to vary the water interaction and hot-pressed to alter the surface structure. Then, multilayers were constructed using polyvinylamine (PVAm) and polyacrylic acid. Both the material surface charge and water interaction affect the amount of polymer adsorbed to the surfaces. Increasing the surface charge decreases the adsorption after the first PVAm layer, possibly due to conformational changes. Periodate-oxidized and crosslinked films have low initial polymer adsorptions; the decreased swelling prevents polymer diffusion into the CNF micropore structure. Microscopic analysis after incubating the samples with bacterial suspensions show that only the materials with the lowest surface charge enable bacteria to adhere to the surface because, when adsorbing up to 5 layers PVAm/PAA, the increased anionic surface charge appears to decrease the net surface charge. Both the amounts of PVAm and PAA influence the net surface charge and thus the bacterial adhesion. The structure generated by the hot-pressing of the films also strongly increases the number of bacteria adhering to the surfaces. These results indicate that the bacterial adhesion to CNF materials can be tailored using polyelectrolyte multilayers on different CNF substrates.

  • 12.
    Henschen, Jonatan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Illergård, Josefin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ek, Monica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Bacterial adhesion to polyvinyl-amine-modified nanocellulose filmsManuscript (preprint) (Other academic)
  • 13.
    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 (London), 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.

  • 14.
    Hollertz, Rebecca
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    López Durán, Verónica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Larsson, Per
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Chemically modified cellulose micro- and nanofibrils as paper-strength additivesManuscript (preprint) (Other academic)
  • 15.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Dimensional Stability of Paper: Influence of Fibre-Fibre Joints and Fibre Wall Oxidation2008Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Paper is a very versatile material. Nevertheless, there are several factors limiting its usefulness, and one of the major issues is that cellulosic and ligno-cellulosic fibres lower their free energy by sorbing water and this water changes the dimensions of the paper. This phenomenon is usually referred to as a lack of dimensional stability and is often evident as misregister during multicolour printing or curl, cockle and wavy edges during printing, copying and storage or, with a wider definition, also as a shortened life-time of boxes during storage due to mechano-sorptive creep.

    The work described in this thesis aims to study and quantify the importance of the different mechanisms causing water-induced dimensional changes in a fibre network and to investigate how to improve the dimensional stability of ligno-cellulosic materials. This has been done both by altering the fiber properties such as the moisture sorptivity and by changing the adhesion and degree of contact within the fibre-fibre joints. The properties of the fibre-fibre joints have been varied by drying laboratory sheets both under restraint and freely to minimise the generation of built-in stresses.

    Bleached kraft fibres were treated using the polyelectrolyte multilayer (PEM) technique to improve the adhesion between the fibres and to increase the molecular contact within the joints. In contrast, the degree of contact was impaired by hornifying the fibres before sheet preparation. For sheets allowed to dry freely, the PEM-treatment increased the hygroexpansion coefficient, i.e. the dimensional movement normalised with respect to the change in moisture content, when subjected to changes in relative humidity whereas the hornification process resulted in a slightly lowered hygroexpansion coefficient. However, when the sheets were dried under restraint, the different joint and fibre modifications led to no difference in hygroexpansion coefficient. This was interpreted as being a result of an increase in the total contact zone between the fibres when the sheets were dried under restraint, with a greater extension in the outof- plain direction of the joint resulting in a transfer of a larger part of the transverse swelling to the in-plane expansion.

    The sorptivity of the fibres was changed by oxidising the C2-C3 bond of the 1,4- glucans with periodate. This most likely created covalent cross-links in the fibre wall both improved the integrity of the fibre wall by locking adjacent fibril lamellae to each other and also removed possible sites for water sorption onto the cellulose surfaces. Periodate oxidation also led to a decrease in the crystallinity of the cellulose within the fibres, making more cellulose hydroxyl groups available for the adsorption of water molecules. This means that the oxidation both decreased and increased the interaction between the fibre wall and moisture but, on two different structural levels. The crosslinks significantly reduced the sorption rate when the papers was subjected to changes in relative humidity, as long as the fibres were not subjected to humidities close to saturation. The smaller change in moisture content when the relative humidity was changed between 20 and 85 % RH meant that the dimensional stability of the crosslinked sheets was increased. On the other hand, the hygroexpansion coefficient was increased in the case of papers made from fibres with the highest degree of oxidation, i.e. the sheets became more sensitive to absolute changes in moisture content.

  • 16.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hygro- and hydroexpansion of paper: Influence of fibre-joint formation and fibre sorptivity2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Paper is a versatile, cheap and environment-friendly material. Nevertheless, there are several factors limiting its usefulness, and one of the major issues is that cellulosic and ligno-cellulosic fibres spontaneously sorb water. At the same time, the water uptake changes the dimensions of the paper. This phenomenon is usually referred to as a lack of dimensional stability and is often evident as misregister during multicolour printing, or curl, cockle and wavy edges during printing, copying, and storage, or, in a widerperspective, as a shortened lifetime of boxes during storage due to mechano-sorptivecreep.

    This thesis aims to improve the understanding of the mechanisms behind the dimensional(in)stability of paper. It looks beyond finding the best starting material and explores what can be done chemically to further improve the dimensional stability. Furthermore, it compares traditional hygroexpansion measurements, where the dimensional change is measured as a function of atmospheric relative humidity, and dimensional changes caused by liquid water, referred to here as hydroexpansion.

    The main parameters which have been studied are the ability of the fibres to join together and their ability to sorb water. In other words, how the degree of molecular contact within the fibre joints, as well as how the fibres are dried, affect the dimensional stability of the final paper, and whether it is possible to reduce the sorptivity of the fibres, and thus their ability to expand, by chemically cross-linking the fibre-wall.

    It was found that the degree of fibre-fibre contact, modified by drying or adsorption of polyelectrolyte multilayers, had little influence on the hygroexpansion or on the hydroexpansion if the sheets were dried under restraint, whereas freely dried sheets with a reduced degree of contact showed a slightly better dimensional stability, at least during hygroexpansion. What, however, had a positive effect on both hygro- and hydroexpansion was the fibre-wall cross-linking. In this work, cross-linking was achieved by oxidising the cellulose to dialdehydecellulose which can form cross-links with adjacent cellulose molecules, and thus reduce the rate of water diffusion into the fibre and hence the uptake of water. In the case of the most oxidised and cross-linked fibres, the diffusion coefficient was found to be 2–3 times lower than that of the non-oxidisedreference. The effect of the cross-linking was, however, the most prominent the first time the moisture content of the paper was increased since cycled samples no longer show this lower adsorption rate. It is suggested that this is due to the formation of a new pore system when the moisture content is increased, and the slow creation of this pore system reduces the moisture uptake of the sample.

    If hygroexpansion is compared with hydroexpansion, it is evident that a given change in moisture content does not correspond to the same absolute expansion, the maximum hydroexpansion being lower by a factor of 2–3 than the hygroexpansion of the same paper. This is probably because the applied liquid water is never equally distributed in the fibre network before it evaporates. Another effect of the more dynamic absorption of liquid water and the subsequent hydroexpansion is that at least in non-restrained samples there is first a rapid initial expansion which is followed 5 to 15 seconds later by a rapid in-plane contraction. It is suggested that this contraction is due to a combination of the release of dried-in strains, drying, and an increase in surface roughness.

  • 17.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. 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 Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Ductile All-Cellulose Nanocomposite Films Fabricated from Core-Shell Structured Cellulose Nanofibrils2014In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 6, p. 2218-2223Article in journal (Refereed)
    Abstract [en]

    Cellulosic materials have many desirable properties such as high mechanical strength and low oxygen permeability and will be an important component in a sustainable biomaterial-based society, but unfortunately they often lack the ductility and formability offered by petroleum-based materials. This paper describes the fabrication and characterization of nanocomposite films made of core-shell modified cellulose nanofibrils (CNEs) surrounded by a shell of ductile dialcohol cellulose, created by heterogeneous periodate oxidation followed by borohydride reduction of the native cellulose in the external parts of the individual fibrils. The oxidation with periodate selectively produces dialdehyde cellulose, and the process does not increase the charge density of the material. Yet the modified cellulose fibers could easily be homogenized to CNFs. Prior to film fabrication, the CNF was shown by atomic force microscopy to be 0.5-2 mu m long and 4-10 nm wide. The films were fabricated by filtration, and besides uniaxial tensile testing at different relative humidities, they were characterized by scanning electron microscopy and oxygen permeability. The strength-at-break at 23 degrees C and 50% RH was 175 MPa, and the films could, before rupture, be strained, mainly by plastic deformation, to about 15% and 37% at 50% RH and 90% RH, respectively. This moisture plasticization was further utilized to form a demonstrator consisting of a double-curved structure with a nominal strain of 24% over the curvature. At a relative humidity of 80%, the films still acted as a good oxygen barrier, having an oxygen permeability of 5.5 mL-mu L/(m(2).24 h.kPa). These properties indicate that this new material has a potential for use as a barrier in complex-shaped structures and hence ultimately reduce the need for petroleum-based plastics.

  • 18.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. 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 Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Highly ductile fibres and sheets by core-shell structuring of the cellulose nanofibrils2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 1, p. 323-333Article in journal (Refereed)
    Abstract [en]

    A greater ductility of cellulosic materials is important if they are to be used in increasingly advanced applications. This study explores the potential for using chemical core-shell structuring on the nanofibril level to alter the mechanical properties of cellulose fibres and sheets made thereof. The structuring was achieved by a selective oxidation of the cellulose C2-C3 bonds with sodium periodate, followed by a reduction of the aldehydes formed with sodium borohydride, i.e. locally transforming cellulose to dialcohol cellulose. The resulting fibres were morphologically characterised and the sheets made of these modified fibres were mechanically tested. These analyses showed a minor decrease in the degree of polymerisation, a significantly reduced cellulose crystal width and a greater ductility. At 27 % conversion of the available C2-C3 bonds, sheets could be strained 11 %, having a stress at break of about 90 MPa, and consequently a remarkable tensile energy absorption at rupture of about 9 kJ/kg, i.e. 3-4 times higher than a strong conventional paper. Zero-span tensile measurements indicated that the treatment increased the ductility not only of sheets but also of individual fibres. This suggests that the amorphous and molecularly more mobile dialcohol cellulose is located as a shell surrounding the crystalline core of the cellulose fibrils, and that, at deformations beyond the yield point, this facilitates plastic deformation both within and between individual fibres.

  • 19.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Ductile cellulose nanocomposite films fabricated from nanofibrillated cellulose after partial conversion to dialcohol cellulose2013Conference paper (Refereed)
    Abstract [en]

    Ductile nanofibrillar nanocomposite films with a strain at break of 18%, and a tensile strength of 185 MPa, have been fabricated from nanofibrillated bleached kraft fibres partially converted to dialcohol cellulose prior to homogenisation. The conversion to dialcohol cellulose was performed by oxidation with sodium periodate to a degree of oxidation of ca. 30%, followed by reduction with sodium borohydride, and the fabricated films consequentially had one stiff cellulose phase and one flexible dialcohol cellulose phase. The liberated nanofibrils were characterised by AFM, after adsorption onto a silica surface, and imaging in tapping mode showed a blend of elementary fibrils with a width of 5 nm and inter-entangled fibril aggregates with a width of 15-20 nm. Besides good mechanical properties, the films also provided good barrier properties; at 0% RH the oxygen permeability was 2 ml·µm/(m2·d·kPa).

  • 20.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gimaker, Magnus
    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.
    The influence of periodate oxidation on the moisture sorptivity and dimensional stability of paper2008In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 15, no 6, p. 837-847Article in journal (Refereed)
    Abstract [en]

    The hygroexpansion of paper was significantly reduced, up to 28% lower amplitude of change when the paper was subjected to a change in relative humidity from 20 to 85% RH, by oxidation of the fibre wall. Never-dried bleached kraft fibres were oxidised with sodium periodate, which specifically oxidises the C2-C3 bond of 1,4-glucans so that the cellulose is partly converted into dialdehyde cellulose. Since both the dry and wet strength of laboratory sheets were significantly improved, the dry tensile strength increased from 24 kNm/kg up to 66 kNm/kg and the relative wet tensile strength increased from 1.5% up to 40%, it is suggested that the aldehydes form hemiacetal linkages within the fibre wall during the consolidation and drying of the sheets. The mechanical, hygroexpansive and moisture sorptive properties of the sheets made from the oxidised fibres were studied. The results showed that the main reason for the reduced hygroexpansion was a decrease in moisture sorptivity, i.e. when the sheets made of fibres with different degrees of cross-linking were subjected to the same change in relative humidity, the more cross-linked fibres showed a smaller change in moisture content. It was also shown that the hygroexpansion coefficient, i.e. the moisture-normalised dimensional change, was not significantly changed by the periodate oxidation, i.e. indicating that there are no improvement in dimensional stability if the paper is subjected to a specific amount of water.

  • 21.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hoc, Miroslav
    Innventia AB, Stockholm.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    A novel approach to study the hydroexpansion mechanisms of paper using spray technique2009In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, no 4, p. 371-380Article in journal (Refereed)
    Abstract [en]

    A new method has been developed to measure the dimensional stability of printing paper by measuring the impact of liquid water on the in-plane dimensional change, i.e. the hydroexpansion, without any simultaneous mechanical interference that can occur when water is pressed into the sheet. This was achieved by using a specially developed spray technique and using electronic speckle photography to continuously measure the dimensional change as water is applied.

    The in-plane expansion for a given change in moisture content was found to be lower in the case of hydroexpansion than for earlier reported hygroexpansion. After the initial expansion following the water application, it was found that sheets rapidly start to contract again already 10-20 seconds after being wetted, i.e. despite still having a fairly constant and significantly higher moisture content than the initial moisture content before water application. These effects suggest that there are different mechanisms behind hydroexpansion than hygroexpansion of paper, and that hygroexpansion measurements should be extrapolated with caution when evaluating papers with respect to printability.

  • 22.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hoc, Miroslav
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    The Influence Of Grammage, Moisture Content, Fibre Furnish And Chemical Modifications On The Hygro- And Hydro-Expansion Of Paper2009In: ADVANCES IN PULP AND PAPER RESEARCH, OXFORD 2009, VOLS 1-3 / [ed] IAnson, SJ, 2009, p. 355-388Conference paper (Refereed)
    Abstract [en]

    The conventional way to evaluate dimensional stability, regardless of end-use purpose, is to measure the change in dimensions when the moisture content is changed by changing the relative humidity. Sorption of moisture from moist air is a relatively slow process and for the evaluation of printing papers this may not be the most appropriate method. In the present work, data from conventional hygroexpansion measurements has been compared with data from hydroexpansion measurements, i.e. expansions caused by the sorption of liquid water, sprayed onto papers printed with a random speckle pattern, the expansion being monitored by electronic speckle photography. Sheets made from different pulps, with different fines contents and different modifications were studied at different grammages and water-transfer levels. The effect of drying-mode, i.e. restrained drying or free drying, was also studied. It was concluded that sheets expand less with a given amount of adsorbed water when it is sorbed in liquid form rather than from moist air. Chemical treatments known to increase both the dry and the wet strength, e.g. polyelectrolyte multilayers and cross-linking through periodate oxidation, did not significantly improve the dimensional stability when the papers were exposed to liquid water.

  • 23.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Kochumalayil, Joby J.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Oxygen and water vapour barrier films with low moisture sensitivity fabricated from self-crosslinking fibrillated cellulose2013In: Advances in pulp and paper research, Cambridge 2013: transactions of the 15th Fundamental Research Symposium held in Cambridge: September 2013, Lancashire, UK: Bury, Lancashire : The Pulp Fundamental Research Society , 2013, , p. 16p. 851-866Conference paper (Refereed)
    Abstract [en]

    To replace petroleum-based barriers used in, for example, packaging applications with a bio-based alternative, the sensitivity to moisture must be lowered. The present work describes the fabrication and characterisation of cellulose-based films with remarkably improved oxygen and water-vapour-barrier properties at 80% relative humidity. This was achieved by fabricating films of self-cross-linking fibrillated cellulose after partial periodate oxidation to dialdehyde cellulose. At a relative humidity of 80%, films made of 27% and 44% oxidised cellulose, respectively, showed less than half the permeability of the untreated reference; 3.8 g·mm/(m2·24 h·kPa) and 3.7 g·mm/(m2·24 h·kPa) compared to 8.0 g·mm/(m2·24 h·kPa). This was presumably due to a lower moisture uptake in the films, and consequently less swelling. In the absence of moisture, films from both unmodified and modified fibrillated cellulose were ideal oxygen barriers, but at a relative humidity of 80%, films based on 27% and 44% converted cellulose had an oxygen permeability of 2.2 ml·µm/(m2·24 h·kPa) and 1.8 ml·µm/(m2·24 h·kPa), respectively, compared to 9.2 ml·µm/(m2·24 h·kPa) for the non-oxidised material.

    The cross-linking resulted in an embrittlement of the films, but the 27% oxidised material still had a tensile strength of 148 MPa and a tensile strain at break of 2.0%, which is sufficient in, for example, many packaging applications.

  • 24.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Cross-linked barrier films with low sensitivity to relative humidity fabricated from nanofibrillated cellulose2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 256-CELL-Article in journal (Other academic)
  • 25.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Improved barrier films of cross-linked cellulose nanofibrils: a microscopy study2014In: Green materials, ISSN 2049-1220, Vol. 2, no 4, p. 163-168Article in journal (Refereed)
    Abstract [en]

    It is highly desirable to replace gas barriers of aluminium and non-renewable plastics in order to lower our ecological footprint. One interesting candidate is films made from cellulose nanofibrils (CNFs), which after cross-linking have been shown to have competitive barrier properties even at a high relative humidity (80% RH). This work presents studies at even higher relative humidity (90% RH) and microscopic studies of what happens when unmodified and cross-linked CNF films are exposed to water. The microscopy techniques used were scanning electron microscopy of dry and wet cross-sections of films after freeze-drying and atomic force microscopy in the dry state and in the wet state shortly after wetting. Both techniques clearly revealed that the cross-links prevent the CNFs from separating from each other and hence prevent the films from swelling, so that the free-volume-sensitive gas permeability is maintained at a low level.

  • 26.
    Larsson, Per A.
    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.
    Diffusion-induced dimensional changes in papers and fibrillar films: influence of hydrophobicity and fibre-wall cross-linking2010In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 17, no 5, p. 891-901Article in journal (Refereed)
    Abstract [en]

    The initial dimensional stability of paper measured as hydroexpansion, i.e. when paper is exposed to liquid water, has been considerably improved by combining a periodate-oxidation-induced cross-linking of the fibre wall with the subsequent adsorption of a hydrophobic polyelectrolyte multilayer consisting of three layers of poly(allylamine hydrochloride) and two layers of poly(acrylic acid). This reduced the rate of diffusion of water into the fibre wall at the same time as the diffusion distance was increased, i.e. the water has to diffuse all the way from the top of the sheet and not only from the individual fibre surfaces since capillary absorption was prevented. However, as a consequence, the hydrophobic sheets present a greater expansion maximum before contraction. It is suggested that this may be due to a higher moisture content in the top fibre layers of the hydrophobically modified papers than in the hydrophilic sheets, since all the water is concentrated to the top fibre layers of the hydrophobic papers. Sheets made from bleached kraft pulp or thermo-mechanical pulp as well as model sheets made from microfibrillated cellulose (MFC) were studied. The MFC-sheets were intended as a model of the fibre wall, i.e. a sheet without any fibre joints. The behaviour of the MFC-sheets was similar to that of ordinary sheets when subjected to water, which indicates that the properties of the fibre joints do not affect the hydroexpansion to any great content and that the expansion of the paper is directly linked to the expansion of the fibre wall.

  • 27.
    Larsson, Per A.
    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.
    Influence of fibre-fibre joint properties on the dimensional stability of paper2008In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 15, no 4, p. 515-525Article in journal (Refereed)
    Abstract [en]

    Measurements have been performed to clarify the connection between fibre-fibre joint properties and dimensional stability using laboratory sheets prepared from never-dried fibres, from heavily hornified fibres having a low molecular contact area between the fibres, and from both hornified and never-dried fibres treated with a polyelectrolyte multilayer (PEM) technique to increase the molecular contact area in the fibre-fibre joint. The influence of the drying mode, i.e. whether the sheets are dried freely or under restraint, was also evaluated. The results showed that neither paper strength nor fibre-fibre joint contact area had any significant influence on the dimensional stability of sheets dried under restraint. On the other hand, when the sheets were dried freely, the PEM-treated sheets expanded to the same extent as, or to an even greater extent than the non-PEM-treated sheets, even though they adsorbed less water for a given change in relative humidity. There was also a correlation between drying shrinkage and dimensional stability, where greater shrinkage was associated with a greater hygroexpansion in the freely dried sheets.

  • 28.
    Larsson, Per A.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Towards natural-fibre-based thermoplastic films produced by conventional papermaking2016In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 18, no 11, p. 3324-3333Article in journal (Refereed)
    Abstract [en]

    Materials based on cellulose are predicted to be of great importance in a sustainable society. However, for materials such as paper to replace materials with a higher ecological footprint, they need to be strong, ductile, provide a gas barrier, and, sometimes, also be transparent. Improved properties, or even novel properties, are also important for use outside the conventional markets. This paper describes how cellulose fibres partly derivatised to dialcohol cellulose can be used to fabricate high-density materials by conventional papermaking techniques that simultaneously display all the above-mentioned features. The materials produced were characterised with respect to X-ray diffraction, dynamic mechanical thermal behaviour, visual appearance, oxygen permeability and tensile properties. The highest degree of modification studied, resulted in a material with thermoplastic features, a tensile strength of 57 MPa, a strain-at break of 44% and an oxygen permeability at 80% RH of 23 ml mu m (m(2) kPa 24 h)(-1). At a thickness of 125 mu m, these films have a total light transmittance of 78% (87% haze). However, by hot pressing the film for 2 min at 150 degrees C under a pressure of 16 MPa, and thereby increasing the density, the total transmittance increases to 89% (23% haze). The hot pressing can also be used to fuse individual pieces together, which is useful in many modern packaging applications. Altogether, this work shows how chemical modification of cellulose fibres can be used to induce novel properties and improve the range of application, and consequently provide an interesting bio-based material with a good potential to replace less sustainable materials.

  • 29.
    Linvill, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Advanced three-dimensional paper structures: Mechanical characterization and forming of sheets made from modified cellulose fibers2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 128, p. 231-240Article in journal (Refereed)
    Abstract [en]

    Cellulose partially converted to dialcohol cellulose has been identified as a potential breakthrough material for the production of bio-based, complex, double-curved surfaces due to its extensive strain-at-break characteristics (reaching as great as 80% in tensile loading). Tensile testing of handsheets made from modified cellulose fibers was conducted from 50 to 90% relative humidity (RH) and from 23 to 150 °C. Strain-at-break of the handsheets ranged from 35 to 80% over this humidity and temperature range, which is significantly greater than typical cellulose-based materials. The combined effect of moisture and temperature was further investigated by dynamic mechanical thermal analysis, which was utilized to determine the glass-transition temperature of the handsheets as a function of relative humidity. Based on the tensile test results and verified by the three-dimensional (3-D) forming and simulation, a forming limit diagram (strain-based failure surface which describes and illustrates the formability of the material) for the handsheets was generated. This forming limit illustrates significant extent to which this bio-based material can be 3-D formed into advanced structures. Furthermore, temperature was identified as the best, quickest, and most controllable method of improving extensibility of this material during 3-D forming.

  • 30.
    Linvill, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Biofibre Materials Centre, BiMaC.
    Larsson, Per
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. TU Dresden, Fakultät Maschinenwissen, Institut für Verarbeitungsmaschinen und Mobile Arbeitsmaschinen .
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Advanced Three-Dimensional Paper Structures: Mechanical Characterization and Forming of Sheets Made from Modied Cellulose Fibers2017Report (Other academic)
  • 31.
    Linvill, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Östlund, Sören
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Dynamic Mechanical Thermal Analysis Data of Sheets Made from Wood-Based Cellulose Fibers Partially Converted to Dialcohol Cellulose2017In: Data in Brief, ISSN 2352-3409, Vol. 14, p. 504-506Article in journal (Refereed)
    Abstract [en]

    This data article contains the dynamic mechanical thermal analysis (DMTA) results for sheets made from cellulose fibers partially converted to dialcohol cellulose as presented in “Advanced Three-Dimensional Paper Structures: Mechanical Characterization and Forming of Sheets Made from Modified Cellulose Fibers” by Linvill et al. [1]. See Larsson and Wågberg [2] for a description and characterization of the material as well as how the material is produced. The DMTA tests were conducted at four different relative humidity levels: 0, 50, 60, and 70% RH, and the temperature was swept between 10 and 113 °C. The DMTA results enable the understanding of the elastic, viscoelastic, and viscoplastic mechanical properties of this material at a wide range of temperature and relative humidity combinations.

  • 32. Lombardo, S.
    et al.
    Chen, Pan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Larsson, Per A.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Thielemans, W.
    Wohlert, Jakob
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Svagan, Anna J.
    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.
    Toward Improved Understanding of the Interactions between Poorly Soluble Drugs and Cellulose Nanofibers2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 19, p. 5464-5473Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibers (CNFs) have interesting physicochemical and colloidal properties that have been recently exploited in novel drug-delivery systems for tailored release of poorly soluble drugs. The morphology and release kinetics of such drug-delivery systems heavily relied on the drug-CNF interactions; however, in-depth understanding of the interactions was lacking. Herein, the interactions between a poorly soluble model drug molecule, furosemide, and cationic cellulose nanofibers with two different degrees of substitution are studied by sorption experiments, Fourier transform infrared spectroscopy, and molecular dynamics (MD) simulation. Both MD simulations and experimental results confirmed the spontaneous sorption of drug onto CNF. Simulations further showed that adsorption occurred by the flat aryl ring of furosemide. The spontaneous sorption was commensurate with large entropy gains as a result of release of surface-bound water. Association between furosemide molecules furthermore enabled surface precipitation as indicated by both simulations and experiments. Finally, sorption was also found not to be driven by charge neutralization, between positive CNF surface charges and the furosemide negative charge, so that surface area is the single most important parameter determining the amount of sorbed drug. An optimized CNF-furosemide drug-delivery vehicle thus needs to have a maximized specific surface area irrespective of the surface charge with which it is achieved. The findings also provide important insights into the design principles of CNF-based filters suitable for removal of poorly soluble drugs from wastewater.

  • 33.
    López Durán, Vernica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    On the relationship between fibre composition and material properties following periodate oxidation and borohydride reduction of lignocellulosic fibres2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 6, p. 3495-3510Article in journal (Refereed)
    Abstract [en]

    Periodate oxidation followed by borohydride reduction was performed on four structurally different pulp fibres to clarify the effect of chemical composition on the structural and mechanical properties of sheets made from these fibres. The main purpose was to explore the possibility of extending the use of lignocellulose fibres in novel applications. The degree of oxidation, morphological changes, chemical and physical structure of the fibres, the supramolecular ordering of the cellulose and the mechanical performance of handsheets made from the fibres were studied. The results showed that both periodate oxidation and borohydride reduction are more reactive towards the carbohydrates of the fibres and as a result, there is an improvement in the tensile properties of the sheets. If the carbohydrates of the fibres are only periodate oxidised to produce dialdehydes, inter- and intra-fibre crosslinks can be formed, leading to paper with increase strength and higher stiffness. The borohydride reduction results in fibres and papers with a greater strength and ductility. It was also found that the characteristic ductility of these modified papers, emanating from the dialcohol cellulose produced, is limited with lignin-rich fibres.

  • 34.
    López Durán, Veronica
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology. KTH Royal Inst Technol, Fibre & Polymer Technol, Teknikringen 56-58, SE-10044 Stockholm, Sweden.;KTH Royal Inst Technol, BiMaC Innovat, Teknikringen 56-58, SE-10044 Stockholm, Sweden..
    Erlandsson, Johan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Larsson, Per A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Novel, Cellulose-Based, Lightweight, Wet-Resilient Materials with Tunable Porosity, Density, and Strength2018In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 6, no 8, p. 9951-9957Article in journal (Refereed)
    Abstract [en]

    Highly porous materials with low density were developed from chemically modified cellulose fibers using solvent-exchange and air drying. Periodate oxidation was initially performed to introduce aldehydes into the cellulose chain, which were then further oxidized to carboxyl groups by chlorite oxidation. Low-density materials were finally achieved by a second periodate oxidation under which the fibers self-assembled into porous fibrous networks. Following a solvent exchange to acetone, these networks could be air-dried without shrinkage. The properties of the materials were tuned by mechanical mixing with a high intensity mixer for different times prior to the second periodate oxidation, which resulted in porosities between 94.4% and 96.3% (i.e., densities between 54 and 82 kg/m(3)). The compressive strength of the materials was between 400 and 1600 kPa in the dry state and between 20 and 50 kPa in the wet state. It was also observed that in the wet state the fiber networks could be compressed up to 80% while still being able to recover their shape. These networks are highly interesting for use in different types of absorption products, and since they also have a high wet integrity, they can be modified with physical methods for different high-value-added end-use applications.

  • 35. López Durán, Verónica
    et al.
    Erlandsson, Johan
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Larsson, Per A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Novel cellulose-based light weight, wet resilient materials with tunable porosity, density and strengthManuscript (preprint) (Other academic)
  • 36. López Durán, Verónica
    et al.
    Hellwig, Johannes
    Larsson, P. Tomas
    Wågberg, Lars
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Larsson, Per A.
    KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Effect of chemical functionality on the mechanical and barrier performance of all-cellulose compositesManuscript (preprint) (Other academic)
  • 37.
    López Durán, Verónica
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Chemical modification of cellulose-rich fibres to clarify the influence of the chemical structure on the physical and mechanical properties of cellulose fibres and thereof made sheets2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 182, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Despite the different chemical approaches used earlier to increase the ductility of fibre-based materials, it has not been possible to link the chemical modification to their mechanical performance. In this study, cellulose fibres have been modified by periodate oxidation, alone or followed either by borohydride reduction, reductive amination or chlorite oxidation. In addition, TEMPO oxidation, and TEMPO oxidation in combination with periodate oxidation and further reduction with sodium borohydride have also been studied. The objective was to gain understanding of the influence of different functional groups on the mechanical and structural properties of handsheets made from the modified fibres. It was found that the modifications studied improved the tensile strength of the fibres to different extents, but that only periodate oxidation followed by borohydride reduction provided more ductile fibre materials. Changes in density, water-holding capacity and mechanical performance were also quantified and all are dependent on the functional group introduced.

  • 38. Salmén, L.
    et al.
    Larsson, Per A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    On the origin of sorption hysteresis in cellulosic materials2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 182, p. 15-20Article in journal (Refereed)
    Abstract [en]

    Moisture sorption and moisture sorption hysteresis of carbohydrates are phenomena which affect the utilisation of products made thereof. Although extensively studied, there is still no consensus regarding the mechanisms behind sorption hysteresis. Attempts have been made to link the behaviour to molecular properties, in particular to softening properties, and the moisture sorption hysteresis has therefore here been investigated by modifying cellulosic fibres to affect their softening properties. The results show that the moisture sorption hysteresis diminishes with decreasing softening temperature, and was even completely absent at the higher degrees of modification. The moisture sorption characteristics also changed from a type II sorption to a more type III sorption behaviour, a feature more prominent the higher the degree of modification and the higher the temperature. For the highest degree of modification studied the sorption characteristics changed from sorbing less water the higher the temperature to sorbing more water with increasing temperature.

  • 39.
    Tchang Cervin, Nicholas
    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.
    Johansson, Erik
    Larsson, Per
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Bergström, Lennart
    Stockholm University.
    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.
    Strong, water-resistant foams from oven-dried Pickering foams of cellulose nanofibrilsManuscript (preprint) (Other academic)
1 - 39 of 39
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