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  • 151.
    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.

  • 152.
    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.

  • 153.
    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.

  • 154.
    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.

  • 155.
    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.

  • 156.
    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.

  • 157.
    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.

  • 158.
    Larsson, Per Tomas
    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.
    Svensson, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    A new, robust method for measuring average fibre wall pore sizes in cellulose I rich plant fibre walls2013In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 2, p. 623-631Article in journal (Refereed)
    Abstract [en]

    A new, robust method for measuring the average pore size of water-swollen, cellulose I rich fibres is presented. This method is based on the results of solid-state NMR, which measures the specific surface area (area/solids mass) of water-swollen samples, and of the fibre saturation point (FSP) method, which measures the pore volume (water mass/solids mass) of water-swollen samples. These results are suitable to combine since they are both recorded on water-swollen fibres in excess water, and neither requires the assumption of any particular pore geometry. The new method was used for three model samples and reasonable average pore size measurements were obtained for all of them. The structural characterization of water-swollen samples was compared with the dry structure of fibres as revealed using BET nitrogen gas adsorption after a liquid exchange procedure and careful drying. It was concluded that the structure of the water-swollen fibres sets an upper limit on what is obtainable in the dry state.

  • 159.
    Leijonmarck, Simon
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Flexible nano-paper-based positive electrodes for Li-ion batteries- Preparation process and properties2013In: Nano Energy, ISSN 2211-2855, Vol. 2, no 5, p. 794-800Article in journal (Refereed)
    Abstract [en]

    Flexible battery solutions is an emerging field due to a demand for bendable electronic devices. In this study, a route to make flexible positive electrodes for Li-ion batteries by utilizing nanofibrillated cellulose (NFC) as binder material has been examined. These LiFePO4-based electrodes are made by filtration of a water dispersion of NFC, LiFePO4 and Super-P carbon particles, resembling a paper-making process. The resulting electrodes show good mechanical properties both dry as well as when soaked with battery electrolyte with a stress at break of typically at 5.2 and 2.2 MPa, respectively. The cycling performance was 151 mAh/g at C/10 and 132 mAh/g at 1C for samples dried at 170 degrees C. The drying temperature, after the filtration step, was found to be important and to affect both the mechanical properties, rendering the electrodes more ductile at lower temperatures, as well as the electrochemical properties, causing a higher coulombic efficiency at higher temperatures.

  • 160.
    Leijonmarck, Simon
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cornell, Ann
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose2013In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 1, no 15, p. 4671-4677Article in journal (Refereed)
    Abstract [en]

    Recently, a need for mechanically flexible and strong batteries has arisen to power technical solutions such as active RFID tags and bendable reading devices. In this work, a method for making flexible and strong battery cells, integrated into a single flexible paper structure, is presented. Nano-fibrillated cellulose (NFC) is used both as electrode binder material and as separator material. The battery papers are made through a paper-making type process by sequential filtration of water dispersions containing the battery components. The resulting paper structure is thin, 250 mm, and strong with a strength at break of up to 5.6 MPa when soaked in battery electrolyte. The cycling performances are good with reversible capacities of 146 mA h g(-1) LiFePO4 at C/10 and 101 mA h g(-1) LiFePO4 at 1 C. This corresponds to an energy density of 188 mW h g(-1) of full paper battery at C/10.

  • 161.
    Lindström, Stefan
    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.
    Karabulut, Erdem
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Discriminating between different mechanosorptive creep hypotheses2011In: Progress in Paper Physics Seminar 2011: Conference Proceedings / [ed] U. Hirn, Graz: Verlag der Technischen Universität Graz , 2011, p. 121-126Conference paper (Refereed)
  • 162.
    Marais, Andrew
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Tailored cellulosic materials by physical adsorption of polyelectrolytes2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The growing interest in using bio-based resources has made forest-based cellulose (used as fibre and nanofibril building elements) a good candidate for the development of new materials. In order to be used in commercial applications, cellulose must however be processed and/or functionalized to provide the final material with specific properties. This thesis presents (a) a way to improve the mechanical properties of traditional cellulose-based materials (paper), (b) an investigation into the structural and adhesive properties of the self-assembled hyaluronic acid thin films used to tailor the mechanical properties of paper materials, and (c) the preparation and functionalization of cellulose aerogels.

    In the first part of this thesis, the adsorption of polyelectrolytes onto pulp fibres (either as a monolayer or as multilayers) was studied as a way to improve the mechanical properties of paper materials. It was found that low amounts of adsorbed cationic amines were able to significantly improve the tensile properties of sheets made from treated fibres. Tensile testing of fibre crosses and microtomography revealed that this improvement in mechanical properties was due to an increase in both the interfibre joint strength and the interfibre contact area. By building up polyelectrolyte multilayers of hyaluronic acid (HA) and polyallylamine hydrochloride (PAH) onto the fibres, a threefold increase in both strain at break and tensile strength was achieved.

    Finally, wet-resilient porous cellulose aerogels were developed by freezedrying and crosslinking cellulose nanofibrillar gels. This material with high porosity and a high specific surface area was then used as a template to build three dimensional (3D) energy-storage devices using the Layer-by-Layer approach. Thin films of conductive materials were ivdeposited into the bulk of the material, and 3D-interdigitated supercapacitors and batteries were built. The devices showed high capacitance and operated under extreme conditions of compression and bending, opening up numerous possibilities in the field of flexible electronics.

  • 163.
    Marais, Andrew
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Tailoring fibre and paper properties using physical adsorption of polyelectrolytes2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The adsorption of polyelectrolytes, both as monolayers and as multilayers, was investigated as an easy and non-expensive way of producing lignocellulosic fibrous materials with enhanced mechanical properties.

    In the first part of the work described in this thesis, the adsorption of a polyelectrolyte monolayer onto the surface of unbleached and unbeaten kraft pulp fibres with different kappa numbers was investigated. Adsorption isotherms were obtained in order to determine the amounts of polymer that could be adsorbed by the different pulps. Handsheets were made from the treated fibres and the mechanical properties were studied. The results showed that the use of only 2 mg/g of a polymeric amine such as polyallylamine or polyvinylamine could under certain conditions increase the tensile strength index by up to 50 %.

    In a second investigation, the Layer-by-Layer deposition technique was used to build up polyelectrolyte multilayers on the surfaces of bleached kraft pulp fibres. Two systems were studied and the presence of added salt in the systems was also investigated. The results showed that the system composed of polyallylamine hydrochloride and hyaluronic acid provided a dramatic increase in both strength (from 20 Nm/g to 70 Nm/g) and strain at break (from 2.0 % to 6.5 %) with only five deposited bilayers. Such a stretchability could make this material very suitable for 3D-forming of packaging materials.

    The behaviour of this polyallylamine/hyaluronic acid system was then studied from a more fundamental point of view in a third study in order to determine the mechanisms on the nano-scale behind the large improvements observed on the macroscopic paper scale. A quartz crystal microbalance equipment was used to study the adsorption onto model surfaces and show the superlinear trend of the build-up. Atomic force microscopy was also used to study the structural changes occurring upon adsorption of each polymeric layer as well as the adhesive properties of the system.

  • 164.
    Marais, Andrew
    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.
    Magnusson, Mikael S.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.). KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    Joffre, Thomas
    Wernersson, Erik L. G.
    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. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center BiMaC Innovation.
    New insights into the mechanisms behind the strengthening of lignocellulosic fibrous networks with polyamines2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 6, p. 3941-3950Article in journal (Refereed)
    Abstract [en]

    Polyelectrolytes have been used extensively in the papermaking industry for various purposes. Although recent studies have shown that polyamines can be efficient dry-strength additives, the mechanism governing the strength enhancement of paper materials following the adsorption of polyamines onto pulp fibres is still not well understood. In this study, the effect of the adsorption of polyallylamine hydrochloride (PAH) onto the surface of unbleached kraft pulp fibres was investigated on both the fibre and the network scale. Isolated fibre crosses were mechanically tested to evaluate the impact of the chemical additive on the interfibre joint strength on the microscopic scale and the effect was compared with that previously observed on the paper sheet scale. X-ray microtomography was used to understand structural changes in the fibrous network following the adsorption of a polyamine such as PAH. Using image analysis methods, it was possible to determine the number of interfibre contacts (or joints) per unit length of fibre as well as the average interfibre joint contact area. The results showed that the median interfibre joint strength increased by 18 % upon adsorption of PAH. This can be achieved both by a larger molecular contact area in the contact zones and by a stronger molecular adhesion. The addition of the polymer also increased the number of efficient interfibre contacts per sheet volume. This combination of effects is the reason why polyamines such as PAH can increase the dry tensile strength of paper materials.

  • 165.
    Marais, Andrew
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Magnusson, Mikael S.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Joffre, Thomas
    Wernersson, Erik L. G.
    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.
    New insights intothemechanisms behind the strengthening of ligno-cellulosic fibrous networks with polyaminesManuscript (preprint) (Other academic)
  • 166.
    Marais, Andrew
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pendergraph, Samuel
    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.
    Nanometer-Thick Hyaluronic Acid Self-Assemblies with Strong Adhesive Properties2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 28, p. 15143-15147Article in journal (Refereed)
    Abstract [en]

    The adhesive characteristics of poly(allylamine hydrochloride) (PAH)/hyaluronic acid (HA) self-assemblies were investigated using contact adhesion testing. Poly(dimethylsiloxane) spheres and silicon wafers were coated with layer-by-layer (LbL) assemblies of PAH/HA. NO increase in adhesion was observed when surfaces covered With dried LbL films were placed in contact. However, bringing the coated surfaces in contact while wet and separating them after drying resulted in an increase by a factor of 100 in the work of adhesion (from one to three bilayers). Herein we discuss the adhesion in PAH/HA and PAH/poly(acrylic acid) assemblies. PAH/HA assemblies have potential application as strong biomedical adhesives.

  • 167.
    Marais, Andrew
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gustafsson, Emil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    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.
    Towards a super-strainable paper using the Layer-by-Layer technique2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 100, p. 218-224Article in journal (Refereed)
    Abstract [en]

    The Layer-by-Layer technique was used to build a polyelectrolyte multilayer on the surface of pulp fibres. The treated fibres were then used to prepare paper sheets and the mechanical properties of these sheets were evaluated as a function of the number of bi-layers on the fibres. Two different systems were studied: polyethyleneimine (PEI)/nanofibrillated cellulose (NFC), and polyallylamine hydrochloride (PAH)/hyaluronic acid (HA). Model experiments using dual polarization interferometry and SiO2 surfaces showed that the two systems gave different thicknesses for a given number of layers. The outer layer was found to be a key parameter in the PEI/NFC system, whereas it was less important in the PAH/HA system. The mechanical properties of the sheets made from the PAH/HA treated fibres were significantly greater than those made from untreated fibres, reaching 70 Nm/g in tensile index and 6.5% in strain at break. Such a modification could be very useful for 3D forming of paper, opening new perspectives in for example the packaging industry, with a renewable and biodegradable product as a potential substitute for some of the traditional oil-based plastics.

  • 168.
    Mendoza, Ana
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hillborg, H.
    Strömberg, Emma
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Superhydrophobic self-regenerative silicone rubber nanocomposites for electrical outdoor insulation2015In: ICCM International Conferences on Composite Materials, International Committee on Composite Materials , 2015Conference paper (Refereed)
    Abstract [en]

    The overall objective of this project is to develop new structural composite materials for high voltage outdoor insulation applications using silicone rubber (PDMS) coated with micro- and nanoparticles. The goal is to obtain hierarchical superhydrophobic surfaces, with antifogging, antifouling and self-cleaning ability. This will minimize surface leakage currents and subsequent surface flash over of the insulator. In order to achieve both the superhydrophobic and self-cleaning ability, a combination of different surface chemistry of the particles has been investigated. Three different deposition techniques, including spraying of ROD ultrasonicated ZnO suspensions were investigated. Pure silicone rubber (SYLGARD® 184) was coated with hydrophobic and hydrophilic inorganic micro- and nanoparticles (ZnO). The effect of the different factors, such as particle surface chemistry and the deposition method, on the hydrophobicity of the surface has been investigated using static and dynamic contact angle measurements. The objective has been to achieve the highest static contact angle combined with the lowest possible hysteresis. The results showed that the spraying method was more suitable when using PDMS as matrix. The link between superhydrophobicity and the surface structure has been assessed by Scanning Electron Microscopy. The next step towards a self-regenerative composite material is approached by the incorporation of the optimal functionalised nanoparticles into the bulk material. The dynamic behaviour of silicone rubber presents a challenge for the stability of micro- and nanocomposites. Different mechanical techniques and methods of integration are being investigated for improvement of the homogeneity of the composites. Preliminary studies have been performed evaluating the effect of the curing time of the PDMS on the degree of incorporation of the nanoparticles in the surface and uniformity within the bulk. The behaviour of the nanocomposite and the evolution of the different properties with time and environmental conditions will be studied in the next phase of the project. 

  • 169. Naderi, A.
    et al.
    Koschella, A.
    Heinze, T.
    Shih, K. C.
    Nieh, M. P.
    Pfeifer, A.
    Chang, C. C.
    Erlandsson, Johan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Corrigendum to “Sulfoethylated nanofibrillated cellulose: Production and properties” [Carbohydr. Polym. 169 (2017) 515–523] (S0144861717304101) (10.1016/j.carbpol.2017.04.026))2018In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 179Article in journal (Refereed)
    Abstract [en]

    The author Ali Naderi regrets the wrong information given with regard to his affiliation. The author would like to apologise for any inconvenience caused.

  • 170. Naderi, Ali
    et al.
    Koschella, Andreas
    Heinze, Thomas
    Shih, Kuo-Chih
    Nieh, Mu-Ping
    Pfeifer, Annett
    Chang, Chung-Chueh
    Erlandsson, Johan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Sulfoethylated nanofibrillated cellulose: Production and properties2017In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 169, p. 515-523Article in journal (Refereed)
    Abstract [en]

    Sulfoethylated nanofibrillated cellulose (NFCsulf) was produced by an industrially relevant process. The properties of the NFCsulf were compared with those of carboxymethylated nanofibrillated cellulose (NFCcarb), which has been identified as an attractive NFC for several industrial applications. The investigations revealed that NFCsulf is characterized by a higher degree of fibrillation and has superior redispersion properties. Furthermore, NFCsulf displays higher stability in varying pH values as compared to NFCcarb. Hence, NFCsulf may be a more attractive alternative than NFCcarb in applications such as rheological modifiers or adsorbing components in personal care products, in which the performance of NFC must remain unaffected in varying ambient conditions. The superior properties of NFCsulf compared to NFCcarb were proposed to be due to the combination of the unique chemical characteristics of the sulfoethylated reagent, and the larger size of the sulfonate group compared to the carboxymethyl group.

  • 171. Naderi, Ali
    et al.
    Lindstrom, Tom
    Weise, Christoph F.
    Flodberg, Goren
    Sundstrom, Jonas
    Junel, Kristina
    Erlandsson, Johan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Runebjork, AnneMarie
    Phosphorylated nanofibrillated cellulose: production and properties2016In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, no 1, p. 20-29Article in journal (Refereed)
    Abstract [en]

    Phosphate functionalized nanofibrillated cellulose (NFC) was produced through an industrially attractive process, by reacting wood pulp with a phosphate containing salt, followed by mechanical delamination through microfluidization. The degrees of delamination of the phosphorylated NFCs (judged by among others AFM-imaging, rheological studies and tensile strength measurements on NFC films) were found to improve with increasing functionalization of the pulp and number of microfluidization-passes. The NFC systems were found to display similar characteristics as other well-known NFC systems. Interestingly, however, the sufficiently delaminated phosphorylated NFCs exhibited significantly lower oxygen permeability values (at RH 50%) than the published values of several well-known highly delaminated NFC systems. The potential application of the phosphorylated NFC in packaging applications can hence be envisaged.

  • 172. Naderi, Ali
    et al.
    Lindström, Tom
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Biofibre Materials Centre, BiMaC.
    Sundstrom, Jonas
    Carboxymethylated nanofibrillated cellulose: rheological studies2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 3, p. 1561-1571Article in journal (Refereed)
    Abstract [en]

    The rheological properties of carboxymethylated nanofibrillated cellulose (NFC), investigated with controlled shear rate- and oscillatory measurements, are reported for the first time. It was shown that the rheological properties of the studied system are similar to those reported for other NFC systems. The carboxymethylated NFC systems showed among other things high elasticity and a shear thinning behaviour when subjected to increasing shear rates. Further, the shear viscosity and storage modulus of the system displayed power-law relations with respect to the dry content of the NFC suspension. The exponential values, 2 and 2.4 respectively, were found to be in good agreement with both theoretical predictions and published experimental work. Furthermore, it was found that the pulp consistency at which NFC is produced affects the properties of the system. The rheological studies imply that there exists a critical pulp concentration below which the efficiency of the delamination process diminishes; the same adverse effect is also observed when the critical concentration is significantly exceeded due to a lower energy input during delamination.

  • 173.
    Nordgren, Niklas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sandell, Robert
    Berthold, Fredrik
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gamstedt, Kristofer
    Characterization of interfacial stress transfer ability of particulate cellulose composite materials2012Conference paper (Other academic)
  • 174.
    Notley, Shannon
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Eriksson, Malin
    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.
    Visco-elastic and adhesive properties of adsorbed polyelectrolyte multilayers determined in situ with QCM-D and AFM measurements2005In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 292, no 1, p. 29-37Article in journal (Refereed)
    Abstract [en]

     The build-up of multilayers constructed from polyallylamine hydrochloride (PAH) and polyacrylic acid (PAA) under different pH conditions was continuously monitored using the quartz crystal microbalance with dissipation. The adsorbed amount of polymer as well as the amount of coupled water was determined. Furthermore, from dissipation measurements, it was possible to determine the visco-elastic properties of the adsorbed multilayer. These properties were highly dependent on the polyelectrolyte present in the outermost layer. The multilayer was far more rigid and elastic with PAA as the outermost layer. Furthermore, a link has been established between the conformability or rigidity of a multilayer covered surface and the adhesion between such surfaces. Adhesion measurements Using the atomic force microscope showed a greater pull-off force when the more viscous PAH was present in the outermost layer.

  • 175. Notley, S.M.
    et al.
    Eriksson, Malin
    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.
    Beck, S.
    Gray, D.G.
    Surface Forces Measurements of Spin-Coated Cellulose Thin Films with Different Crystallinity2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 7, p. 3154-3160Article in journal (Refereed)
    Abstract [en]

    A systematic study of the surface forces between a cellulose sphere and cellulose thin films of varying crystallinity has been conducted as a function of ionic strength and pH. Semicrystalline cellulose II surfaces and amorphous cellulose films were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose I nanocrystals. These preparation methods produced thin, smooth films suitable for surface forces measurements. The interaction with the cellulose I was monotonically repulsive at pH 3.5, 5.8, and 8.5 and at 0.1, 1, and 10 mM ionic strengths. This was attributed to the presence of strongly ionizable sulfur-containing groups on the cellulose nanocrystal surfaces. The amorphous film typically showed a steric interaction up to 100 nm away from the interface that was independent of the solution conditions. A range of surface forces were successfully measured on the semicrystalline cellulose II films; attractive and repulsive regimes were observed, depending on pH and ionic strength, and were interpreted in terms of van der Waals and electrostatic interactions. Clearly, the forces acting near cellulose surfaces are very dependent on the way the cellulose surface has been prepared.

  • 176.
    Nugroho, Robertus Wahyu N.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Force interactions of grafted polylactide particles2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
  • 177.
    Nugroho, Robertus Wahyu Nayan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Force Interactions of Nonagglomerating Polylactide Particles Obtained through Covalent Surface Grafting with Hydrophilic Polymers2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 26, p. 8873-8881Article in journal (Refereed)
    Abstract [en]

     Nonagglomerating polylactide (PLA) particles with various interaction forces were designed by covalent photografting. PLA particles were surface grafted with hydrophilic poly(acrylic acid) (PAA) or poly(acrylamide) (PAAm), and force interactions were determined using colloidal probe atomic force microscopy. Long-range repulsive interactions were detected in the hydrophilic/hydrophilic systems and in the hydrophobic/hydrophilic PLA/PLA-g-PAAm system. In contrast, attractive interactions were observed in the hydrophobic PLA/PLA and in the hydrophobic/hydrophilic PLA/PLA-g-PAA systems. AFM was also used in the tapping mode to determine the surface roughness of both neat and surface-grafted PLA film substrates. The imaging was performed in the dry state as well as in salt solutions of different concentrations. Differences in surface roughness were identified as conformational changes induced by the altered Debye screening length. To understand the origin of the repulsive force, the AFM force profiles were compared to the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory and the Alexander de Gennes (AdG) model. The steric repulsion provided by the different grafted hydrophilic polymers is a useful tool to inhibit agglomeration of polymeric particles. This is a key aspect in many applications of polymer particles, for example in drug delivery.

  • 178.
    Nyström, Gustav
    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.
    Fall, Andreas
    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.
    Carlsson, Linn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Aligned Cellulose Nanocrystals and Directed Nanoscale Deposition of Colloidal Spheres2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 3, p. 1591-1599Article in journal (Refereed)
    Abstract [en]

    Cellulose nanocrystals are aligned in wrinkled polydimethylsiloxane templates and transferred to polyethyleneimine-coated silica surfaces in a printing process similar to microcontact printing. The highly aligned nanorods were deposited onto the surfaces with a line-to-line distance of 225-600 nm without loss of alignment. It was also possible to repeat the transfer process on the same surface at a 90-degree angle to create a network structure. This demonstrates the versatility of the technique and creates more options for advanced multilayering of materials. To demonstrate that the surface properties of the anionic cellulose nanorods were unaffected by the transfer process and to prove the concept of functionalizing transferred particles, cationic latex particles were electrostatically self-assembled onto the cellulose nanorods. The directed deposition of these particles resulted in excellent site specificity and the highest resolution to date for controlled deposition of colloids on an electrostatically patterned surface.

  • 179.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Fundamentals of Wetting and Mechanical Durability of Superhydrophobic Coatings2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In paper I the friction between three different superhydrophobic surfaces and water drops were investigated using high‑speed video. The surfaces were two based on a hydrophobic wax and the third was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of water drops was measured as a function of drop size and surface inclination. For small capillary numbers it was shown that the dissipation was dominated by pinning‑depinning transitions along the trailing contact line. A parameter called the superhydrophobic sliding resistance bsh has been introduced. The motion of drops on superhydrophobic surfaces of a general macroscopic topography can be predicted provided that bsh and the drop size are known. This theory also infers the existence of an equilibrium sliding angle, beq, at which the drop acceleration is zero.

    The effect of line‑shaped defects on the motion of water drops on superhydrophobic surfaces were also investigated using high‑speed video in paper II. It was shown that the motion of the drop in the vicinity of the defect can be approximated by a damped harmonic oscillator. Whether a drop got trapped or not while traversing the defect was determined by the incident speed and the characteristics of the oscillator. In systems with low viscous dissipation it is possible to predict the trapping speed as well as the exit speed using a simple work‑energy consideration.

    The resistance of wax based superhydrophobic coatings subjected to different types of mechanical damage were investigated in paper III. Scratch tests were performed using atomic force microscopy (AFM) and rubbing with an index finger. Coatings were also subjected to compression with a silicone rubber stamp. The effect of impacting water drops was also investigated. A load of 12 nN was enough to remove the coating from the substrate. The coatings remained superhydrophobic at compression pressures up to 59 kPa but the superhydrophobic properties were lost after only one stroke with a finger. The coatings resisted at least 200 000 impacts of falling water drops without losing their superhydrophobic properties.

    In paper IV superhydrophobic coatings were fabricated in a semi‑continuous process, where an alkyl ketene dimer (AKD) was dissolved in supercritical carbon dioxide (scCO2) and sprayed onto the substrate. Several different substrates such as: glass, aluminium, paper, poly (ethylene terephthalate) (PET) and poly (tetrafluoroethylene) (PTFE) were successfully coated. The most efficient spray process, considering surface properties and mass of extracted AKD, was obtained at the lowest temperature investigated, 67 °C, and the highest pressure evaluated in this study, 25 MPa. The influence of the pre‑expansion conditions (p, T) on the surface temperature (at a spray distance of 3 cm) was also shown to be negligible.

  • 180.
    Olin, Pontus Hans
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    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.
    Influence of tilt angle and droplet size on the sliding rate of water droplets on superhydrophobic surfaces2012Conference paper (Other academic)
  • 181.
    Olin, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hill, Caroline
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ruda, Marcus
    Schimidt, Oskar
    Turner, Charlotta
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Development of a semi-continuous spray process for production of superhydrophobic coatings from supercritical carbon dioxide solutionsManuscript (preprint) (Other academic)
  • 182.
    Olin, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hyll, Caroline
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Metrology and Optics.
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ruda, Marcus
    Schmidt, Oskar
    Turner, Charlotta
    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.
    Development of a Semicontinuous Spray Process for the Production of Superhydrophobic Coatings from Supercritical Carbon Dioxide Solutions2015In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 54, no 3, p. 1059-1067Article in journal (Refereed)
    Abstract [en]

    Superhydrophobic surfaces have been fabricated in a continuous spray process, where an alkyl ketene dimer (AKD) wax is dissolved in supercritical carbon dioxide (scCO(2)) and sprayed onto the substrate. The mass of extracted AKD from scCO2 has been investigated as well as the pressure, temperature, and flow of CO2 at the steady-state spray conditions. Several different substrates such as glass, aluminum, paper, poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) have been successfully coated, and the superhydrophobic properties have been evaluated by measurement of water contact angle, water drop friction, scanning electron microscopy (SEM), and surface topography. The most efficient spray process, considering surface properties and mass of extracted AKD, is obtained at the lowest temperature investigated, 67 degrees C, and the highest pressure evaluated in this study, 25 MPa. We also show that the influence of preexpansion conditions (p, T) on the surface temperature at the selected spray distance (3 cm) is negligible by measurement with an infrared camera during spraying.

  • 183.
    Olin, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Stefan B.
    Pettersson, Torbjörn
    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.
    Water Drop Friction on Superhydrophobic Surfaces2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 29, p. 9079-9089Article in journal (Refereed)
    Abstract [en]

    To investigate water drop friction on superhydrophobic surfaces, the motion of water drops on three different superhydrophobic surfaces has been studied by allowing drops to slide down an incline and capturing their motion using high-speed video. Two surfaces were prepared using crystallization of an alkyl ketene dimer (AKD) wax, and the third surface was the leaf of a Lotus (Nelumbo Nucifera). The acceleration of the water droplets on these superhydrophobic surfaces was measured as a function of droplet size and inclination of the surface. For small capillary numbers, we propose that the energy dissipation is dominated by intermittent pinning-depinning transitions at microscopic pinning sites along the trailing contact line of the drop, while at capillary numbers exceeding a critical value, energy dissipation is dominated by circulatory flow in the vicinity of the contacting disc between the droplet and the surface. By combining the results of the droplet acceleration with a theoretical model based on energy dissipation, we have introduced a material-specific coefficient called the superhydrophobic sliding resistance, b(sh). Once determined, this parameter is sufficient for predicting the motion of water drops on superhydrophobic surfaces of a general macroscopic topography. This theory also infers the existence of an equilibrium sliding angle, beta(eq), at which the drop acceleration is zero. This angle is decreasing with the radius of the drop and is in quantitative agreement with the measured tilt angles required for a stationary drop to start sliding down an incline.

  • 184.
    Olin, Pontus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Lindström, Stefan B.
    Solid Mechanics , Department of Management and Engineering, the Institute of Technology, Linköping 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.
    Trapping of Water Drops by Defects on Superhydrophobic SurfacesManuscript (preprint) (Other academic)
    Abstract [en]

    In this work the effect of line‑shaped defects on the motion of water drops on superhydrophobic surfaces have been investigated using high‑speed video. The defects were introduced on superhydrophobic wax surfaces by a simple scratching method. It is shown that the motion of the drop in the vicinity of the defect can be approximated by a damped harmonic oscillator. Whether a drop gets trapped or not while traversing the defect is determined by the incident speed and the characteristics of the oscillator, more specifically by the damping ratio z and the nondimensional forcing constant â. We also show that it is possible to predict the trapping speed as well as the exit speed using a simple work‑energy consideration in systems with negligible viscous dissipation.

  • 185. Ondaral, Sedat
    et al.
    Ankerfors, Caroline
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Ödberg, Lars
    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.
    Surface-Induced Rearrangement of Polyelectrolyte Complexes: Influence of Complex Composition on Adsorbed Layer Properties2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 18, p. 14606-14614Article in journal (Refereed)
    Abstract [en]

    The adsorption characteristics of two different types of polyelectrolyte complexes (PECs). prepared by mixing poly(allylamine hydrochloride) and poly(acrylic acid) in a confined impinging jet (CIJ) mixer, have been investigated with the aid of stagnation point adsorption reflectometry (SPAR), a quartz crystal microbalance with dissipation (QCM-D), and atomic force microscopy (A FM) using SiO2 surfaces The two sets of PEC were prepared by combining high molecular mass PAH/FAA (PEC-A) and low molt:cubit mass PAH/PAA (PEC-B) The PEC-A showed a higher adsorption to the SiO2 surfaces than the PEC-B The adsorption of the PEC-A also showed a larger change in the dissipation (AD), according to the QCM-D measurements, suggesting that the adsorbed layer of these complexes had a relatively lower viscosity and a lower shear modulus Complementary investigations of the adsorbed layer using A FM imaging showed that the adsorbed layer of PEC-A was significantly different from that of PEC-B and that the changes in properties with adsorption time were very different for the two types of PECs The PEC-A complexes showed a coalescence into larger block of complexes on the SiO2 surface, but this was not detected with the PEC-B The size determinations of the complexes in solution showed that they were very stable over time, and it was therefore concluded that the coalescence of the complexes was induced I the interaction between the complexes and the surface The results also indicated that polyelectrolytes can migrate between the different complexes adsorbed to the surface The results also give indications that the preparation of PEC-B leads to the formation of two different types of polyelectrolyte complexes differing in the amount of polymer in the complexes: i.e., two populations of complexes were formed with similar sizes but with totally different adsorption structures at the solid-liquid interface.

  • 186.
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Superhydrophobic coatings of wax and polymers sprayed from supercritical solutions2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The possibility of using supercritical carbon dioxide (scCO2) as the primary solvent in a spray process for producing superhydrophobic surfaces have been examined in this work. Using scCO2 as solvent will have considerably lower environmental impact compared to an organic solvent since scCO2 is considered a green solvent as it is non-toxic, non-flammable and recyclable. To be able to work at the pressures needed to reach the supercritical state of carbon dioxide, a high-pressure technique called rapid expansion of supercritical solutions (RESS) has been used to produce the coatings. Fluorinated compounds are often used when producing superhydrophobic coatings due to their intrinsic water repellent properties, but generally these compound do not degrade in nature. Due to this, a wax and a biodegradable polymer have been used as the coating materials in this work.

    Two RESS set-ups were used to spray a polymer from solutions of scCO2 and acetone. The first system was based on a continuous flow of the solvent mixture and the polymer particles were collected on silica surfaces. Some of the coatings had superhydrophobic properties and the limitation with this technique was the loss of particles between the nozzle and the surface. In the second set-up, RESS was combined with electrostatic deposition (ED) to improve the particle collection. Different processing parameters were examined and most of the RESS-ED sprayed surfaces were superhydrophobic. This was demonstrated by high contact angles against water, low contact angle hysteresis and low tilt angles at which a water droplet rolls off the surface. It was also shown that the surface structures created when spraying using RESS-ED induced the important two-level roughness that was needed to achieve superhydrophobicity. A semi-continuous process for scaling-up the RESS system when spraying the wax has been developed. Temperature and pressure was investigated to find the highest solubility of the wax in scCO2, and 250 bar and 67 °C resulted in the largest amount of sprayed wax. It was also shown that the system is suitable for spray-coating the wax on different substrates such as glass, paper, aluminium etc. since all of these surfaces showed superhydrophobic properties. The wear resistance of the coatings were examined by different methods. Scratch resistance, vertical compression and the friction between the surface and a finger were analysed. The polymer coated surfaces showed a larger robustness compared with the wax surfaces in the scratch tests. The superhydrophobicity was lost for the wax coatings exposed to compression loads above 59 kPa and in the frictions test, one finger stroke over the coating destroyed the surface roughness. Finally, the wax surfaces were investigated as coating barriers to protect steel from corrosion. The superhydrophobic coating was stable up to 10 days before corrosion of the steel started.

  • 187.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Chigome, S.
    Birkin, Natasha A.
    Howdle, Steven M.
    Torto, N.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Turner, Charlotta
    Superphydrophobic polymeric coatings produced by rapid expansion of supercritical solutions combined with electrostatic deposition (RESS-ED)Manuscript (preprint) (Other academic)
  • 188.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Chigome, Samuel
    Birkin, Natasha A.
    Howdle, Steven M.
    Torte, Nelson
    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.
    Turner, Charlotta
    Superhydrophobic polymeric coatings produced by rapid expansion of supercritical solutions combined with electrostatic depostion (RESS-ED)2014In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 95, p. 610-617Article in journal (Refereed)
    Abstract [en]

    In this paper we present a method to produce superhydrophobic polymeric coatings by combining the rapid expansion of supercritical solutions (RESS) with electrostatic deposition (ED). A copolymer, poly(vinyl acetate)-poly(vinyl pivalate) was dissolved in a mixture of supercritical carbon dioxide and acetone and sprayed through a nozzle with an applied voltage of 8 kV onto a surface placed on a earthed collector. Spray distance and polymer concentration were altered to find the most suitable spraying conditions. Superhydrophobic surfaces were produced when spraying both with and without a voltage, although the water repellent surfaces could be produced at a larger variety of processing parameters using the RESS-ED technique. The greatest improvement of using the RESS-ED process was that larger and thinner coatings were produced with a more even surface coverage of the created polymer particles compared to spraying without the applied voltage.

  • 189.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Meizoso, Irene Rodriguez
    Turner, Charlotta
    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.
    Preparation of polymeric surface coatings by using supercritical carbon dioxide2013In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245Article in journal (Other academic)
  • 190.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pettersson, Torbjörn
    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.
    Wear studies of superhydrophobic coatings of wax and polymers sprayed from rapid expansion of supercritical solutions (RESS)Manuscript (preprint) (Other academic)
  • 191.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Olin, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Tuominen, Mikko
    SP Kemi, Material och Ytor, Drottning Kristinas väg 45, SE-114 86 Stockholm.
    Pettersson, Torbjörn
    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.
    Wear studies of superhydrophobic coatings of wax sprayed from rapid expansion of supercritical solutions (RESS)Manuscript (preprint) (Other academic)
    Abstract [en]

    The wear resistance of superhydrophobic coatings made by spraying a wax from supercritical carbon dioxide solutions have been evaluated by different methods. Scratch tests were performed by using the tip of the cantilever in an atomic force microscope (AFM) by applying an increasing load force on the tip during the measurement. Compression tests were also performed by applying different loads onto a rubber stamp that was placed on the surfaces. In addition to this, frictional wear was evaluated by moving an index finger over the surface using a device that measured the applied load and frictional forces. The wetting properties of the exposed coatings were subsequently evaluated in terms of advancing and receding water contact angles, the superhydrophobic sliding resistance parameter and the surface roughness (RMS). The morphology of the coatings was studied by scanning electron microscopy and optical profilometry. Scratching, with the AFM, at load forces of 12 nN was enough to fully remove the coating from the underlying silica substrate. Results also show that the surfaces remained superhydrophobic after being exposed to compression loads up to 59 kPa. The frictional wear measurments showed that the superhydrophobic properties were immediately lost after pressing and moving a finger over the coating since the lateral movement destroyed the fine surface structure.  Finally it was found that the surfaces could stand up to 200 000 falling water drops without losing its superhydrophobicity.

  • 192.
    Ovaskainen, Louise
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Rodriguez-Meizoso, Irene
    Birkin, Natasha A.
    Howdle, Steven M.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Turner, Charlotta
    Towards superhydrophobic coatings made by non-fluorinated polymers sprayed from a supercritical solution2013In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 77, p. 134-141Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to create a superhydrophobic surface using polymers that are non-fluorinated and applying them to a surface via rapid expansion of a supercritical solution (RESS). Solubility studies of poly(epsilon-caprolactone) (PCL) and a statistical copolymer of vinyl acetate and vinyl pivalate (P(VAc-VPi))in supercritical carbon dioxide (scCO(2)) were carried out using an extraction procedure. It was found that the most suitable process parameters for spraying these polymers using the RESS technique were 30 MPa, 40 degrees C and 10% (v/v) acetone as a co-solvent. The surfaces produced were characterized in terms of their morphology and hydrophobic properties by scanning electron microscopy and contact angle measurements, respectively. The most hydrophobic surfaces were obtained by spraying the P(VAc-VPi) copolymers, giving advancing water contact angles in the range of 120-155 degrees due to the hydrophobic character of the polymer and the microstructure formed with the RESS technique. These results show great promise for the creation of superhydrophobic surfaces using non-fluorinated polymers applied to surfaces via RESS technique.

  • 193.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gustafsson, Emil
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Johansson, Erik
    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.
    JKR approach to study joint formation2010In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY: volume 239, 2010, p. CELL-144-Conference paper (Other academic)
    Abstract [en]

    To gain a more fundamental understanding of the mechanism for joint formation between pulp fibres, we have utilized the JKR approach to study the adhesion properties of multilayers formed using anionic and cationic MFC (microfibrillar cellulose). The effect of using anionic or cationic MFC in the outermost layer has been elucidated and compared with measurements performed on other types of cellulosic model surfaces. Furthermore, our JKR instrument has been modified to enable measurements of the drying process, by comparing the adhesion interaction between PVAm (poly[vinylamine]) coated surfaces that have been dried in contact, or dried before being brought into contact. The typical contact area in the JKR experiments are in the micrometre range and our measurements have been compared with nanoscale adhesion measurements by colloidal probe AFM (atomic force microscopy).

  • 194.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Mohanty, Biwaranjas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dedinaite, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Polyelectrolyte lubrication measured by colloidal probe AFM2010In: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIET: volume 239, 2010, p. COLL-91-Conference paper (Refereed)
    Abstract [en]

    AFM-colloidal probe was used to measure surface interactions and friction forces between polyelectrolyte coated surfaces. We used highly charged polyelectrolyte together with oppositely charged surfactant; that associate in bulk solution and form complexes. Even at the surface, similarly structured polyelectrolyte-surfactant layers were spontaneously formed and the lubrication properties of these layers were highly interesting: having a high load bearing capacity, and very low friction coefficient. Interestingly, when the applied load was increased stepwise the friction force as a function of load displays some sharp peaks, due to structural rearrangements in the polyelectrolyte-surfactant layer. On unloading very low frictional forces was obtained despite the presence of adhesion between the layers. It is shown that in order to maintain favorable lubricating properties it is essential to have the surfactant present in solution, whereas, after the initial polyelectrolyte adsorption step, there is no need to have the polyelectrolyte present in the bulk.

  • 195.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Pendergraph, Samuel A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Marais, Andrew
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Gustafsson, Emil
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Robust and Tailored Wet Adhesion in Biopolymer Thin Films2014In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 12, p. 4420-4428Article in journal (Refereed)
    Abstract [en]

    Model layer-by-layer (LbL) assemblies of poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were fabricated in order to study their wet adhesive behavior. The film characteristics were investigated to understand the inherent structures during the assembly process. Subsequently, the adhesion of these systems was evaluated to understand the correlation between the structure of the film and the energy required to separate these LbL assemblies. We describe how the conditions of the LbL fabrication can be utilized to control the adhesion between films. The characteristics of the film formation are examined in the absence and presence of salt during the film formation. The dependence on contact time and LbL film thickness on the critical pull-off force and work of adhesion are discussed. Specifically, by introducing sodium chloride (NaCl) in the assembly process, the pull-off forces can be increased by a factor of 10 and the work of adhesion by 2 orders of magnitude. Adjusting both the contact time and the film thickness enables control of the adhesive properties within these limits. Based on these results, we discuss how the fabrication procedure can create tailored adhesive interfaces with properties surpassing analogous systems found in nature.

  • 196.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Bergström, Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Adhesive and adsorption properties of a cationic amphiphilic block copolymer for use as compatibilizer in (bio)-composites2011In: EUPOC 2011, Biobased Polymers and Related Biomaterials, 2011Conference paper (Refereed)
    Abstract [en]

    The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This has stimulated a lot of research where cellulosic fibres are combined with different types of polymer matrices to obtain more environmentally friendly composite materials. However, the compatibility between the different components in a composite, which is of decisive importance for its final properties, is a large problem in many systems today. In this work, the objective was to create a novel type of compatibilizer that can physically adsorb onto fibres to enhance the interaction between fibres and non-polar polymer matrices in fibre-reinforced composites, both by addressing surface energies and by introducing polymer entanglements at the interface. This physical route is much more convenient compared to covalent attachment since it can be performed in water under mild conditions and therefore does not require any use of organic solvents for the attachment of the compatibilizer. To achieve this, an amphiphilic block copolymer with one high molecular weight hydrophobic block (polystyrene, PS) and one cationic block (poly(dimethylamino)ethyl methacrylate, PDMAEMA) was synthesized. Due to the cationic charges, the polymers adsorb to oppositely charged surfaces resulting in a measured contact angle close to that of many non-polar polymer matrices. The adhesion, (measured with atomic force microscopy, AFM, using the colloidal probe technique), of the surface with compatibilizer towards a non-polar PS-probe increased with increasing contact time, most probably due to polymer entanglements between the non-polar blocks at the treated surface and the probe. This demonstrates that the use of this type of novel amphiphilic block copolymer is a promising route to improve the compatibility between charged reinforcing materials such as cellulose-based fibres but also glass-fibres, nanoclay, nanofibrillated cellulose and other charged reinforcing materials, and hydrophobic matrices in composite materials. Limitations when designing new materials due to a lack in compatibility could in this way be addressed in an easy but effective way resulting in more environmentally friendly materials with improved mechanical properties.

  • 197.
    Pettersson, Torbjörn
    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.
    Utsel, Simon
    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.
    Particle adhesion and imaging of particle/surface breakage zone2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, no 83, p. 106107-Article in journal (Refereed)
    Abstract [en]

    An AFM methodology to enable measurement of the adhesion of micrometre sized objects, having contact areas in the range of nanometre to micrometer, is reported. The method also enables imaging of the actual breakage zone on both the surface and the removed object to obtain further information regarding the breakage zone. The method is also useful for measuring consolidating systems, such as drying, curing, or annealing systems.

  • 198.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Utsel, Simon
    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.
    Particle adhesion and imaging of particle/surface contact zone2011In: 25th ECIS (European Colloid and Interface Society meeting), 2011Conference paper (Other academic)
    Abstract [en]

    The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This has stimulated alternative research where cellulosic fibres are combined with different types of polymer matrices to obtain more environmentally friendly composite materials. However, the compatibility between the different components in a composite, which is imperative for the properties of the composite, is a large problem in many systems today. In this work, the objective is to evaluate an amphiphilic block copolymer with one high molecular weight hydrophobic block (polystyrene, PS) and one cationic block (poly(di¬methyl-amino)ethyl methacrylate, PDMAEMA), to be used as a compatibilizer between fibres and non-polar polymer matrices in fibre-reinforced composites. The purpose is both to affect the surface energy and to introducing polymer entanglement at the interface. The AFM colloidal probe technique was used to measure the adhesion which is acting in the present work. The adhesive force of a non-polar PS probe towards a surface covered with preadsorbed compatibilizer increased with increasing contact time, due to polymer entanglements between the non-polar blocks at the treated surface and the probe. Also the contact-zone between PS particles and compatibilizer surface was imaged with AFM. This was done by carefully removing pre-adhered PS particles with the aid of AFM cantilevers that was glued onto the particle in-situ followed by pulling. This also enables imaging of the contact zone on both the compatibilizer surface and on the PS particle.

  • 199. Rathje, Li-Sophie Z.
    et al.
    Nordgren, Niklas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Rönnlund, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Aspenström, Pontus
    Gad, Annica K. B.
    Oncogenes induce a vimentin filament collapse mediated by HDAC6 that is linked to cell stiffness2014In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, no 4, p. 1515-1520Article in journal (Refereed)
    Abstract [en]

    Oncogenes deregulate fundamental cellular functions, which can lead to development of tumors, tumor-cell invasion, and metastasis. As the mechanical properties of cells govern cell motility, we hypothesized that oncogenes promote cell invasion by inducing cytoskeletal changes that increase cellular stiffness. We show that the oncogenes simian virus 40 large T antigen, c-Myc, and cyclin E induce spatial reorganization of the vimentin intermediate filament network in cells. At the cellular level, this reorganization manifests as increased width of vimentin fibers and the collapse of the vimentin network. At nanoscale resolution, the organization of vimentin fibers in these oncogene-expressing cells was more entangled, with increased width of the fibers compared with control cells. Expression of these oncogenes also resulted in up-regulation of the tubulin deacetylase histone deacetylase 6 (HDAC6) and altered spatial distribution of acetylated microtubules. This oncogene expression also induced increases in cellular stiffness and promoted the invasive capacity of the cells. Importantly, HDAC6 was required and sufficient for the structural collapse of the vimentin filament network, and was required for increased cellular stiffness of the oncogene-expressing cells. Taken together, these data are consistent with the possibility that oncogenes can induce cellular stiffness via an HDAC6-induced reorganization of the vimentin intermediate filament network.

  • 200.
    Salajkova, Michaela
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Cervin, Nicholas
    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.
    Schülz, Christina
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Stockholm University.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    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.
    Salazar Alvarez, German
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Stockholm University.
    Super-slippery omniphobic self-standing films and coatings based on nanocelluloseManuscript (preprint) (Other academic)
12345 151 - 200 of 243
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