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  • 1. Chernyy, Sergey
    et al.
    Järn, Mikael
    Shimizu, Kyoko
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pedersen, Steen Uttrup
    Daasbjerg, Kim
    Makkonen, Lasse
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Iruthayaraj, Joseph
    Superhydrophilic Polyelectrolyte Brush Layers with Imparted Anti-Icing Properties: Effect of Counter ions2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 9, p. 6487-6496Article in journal (Refereed)
    Abstract [en]

    This work demonstrates the feasibility of superhydrophilic polyelectrolyte brush coatings for anti-icing applications. Five different types of ionic and nonionic polymer brush coatings of 25-100 nm thickness were formed on glass substrates using silane chemistry for surface premodification followed by polymerization via the SI-ATRP route. The cationic [2-(methacryloyloxy)ethyl]trimethylammonium chloride] and the anionic [poly(3-sulfopropyl methacrylate), poly(sodium methacrylate)] polyelectrolyte brushes were further exchanged with H+, Li+, Na+, K+, Ag+, Ca2+, La3+, C16N+, F-, Cl-, BF4-, SO42-, and C12SO3- ions. By consecutive measurements of the strength of ice adhesion toward ion-incorporated polymer brushes on glass it was found that Li+ ions reduce ice adhesion by 40% at 18 degrees C and 70% at 10 degrees C. Ag+ ions reduce ice adhesion by 80% at -10 degrees C relative to unmodified glass. In general, superhydrophilic polyelectrolyte brushes exhibit better anti-icing property at -10 degrees C compared to partially hydrophobic brushes such as poly(methyl methacrylate) and surfactant exchanged polyelectrolyte brushes. The data are interpreted using the concept of a quasi liquid layer (QLL) that is enhanced in the presence of highly hydrated ions at the interface. It is suggested that the ability of ions to coordinate water is directly related to the efficiency of a given anti-icing coating based on the polyelectrolyte brush concept.

  • 2.
    Ejenstam, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ovaskainen, Louise
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Rodriguez-Meizoso, I.
    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.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    The effect of superhydrophobic wetting state on corrosion protection - The AKD example2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 412, p. 56-64Article in journal (Refereed)
    Abstract [en]

    Corrosion is of considerable concern whenever metal is used as construction material. In this study we address whether superhydrophobic coatings could be used as part of an environmentally friendly corrosion-protective system, and specific focus is put on how the wetting regime of a superhydrophobic coating affects corrosion inhibition. Superhydrophobic alkyl ketene dimer (AKD) wax coatings were produced, using different methods resulting in hierarchical structures, where the coatings exhibit the same surface chemistry but different wetting regimes. Contact angle measurements, ESEM, confocal Raman microscopy, open circuit potential and electrochemical impedance spectroscopy were used to evaluate the surfaces. Remarkably high impedance values of 1010Ωcm2 (at 10-2Hz) were reached for the sample showing superhydrophobic lotus-like wetting. Simultaneous open circuit potential measurements suggest that the circuit is broken, most likely due to the formation of a thin air layer at the coating-water interface that inhibits ion transport from the electrolyte to the metal substrate. The remaining samples, showing superhydrophobic wetting in the rose state and hydrophobic Wenzel-like wetting, showed less promising corrosion-protective properties. Due to the absence of air films on these surfaces the coatings were penetrated by the electrolyte, which allowed the corrosion reaction to proceed.

  • 3.
    Ejenstam, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Towards superhydrophobic polydimethylsiloxane-silica particle coatings2016In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 37, no 9, p. 1375-1383Article in journal (Refereed)
    Abstract [en]

    Hydrophobized silica nanoparticles of different sizes, from 16 to 500 nm, were used to impart roughness to a hydrophobic polydimethylsiloxane (PDMS) coating with the aim of obtaining superhydrophobic properties. The particle silanization process and the curing process of the PDMS coating were optimized to increase the contact angle of the particle containing coating. The evaluation of the coatings, by means of water contact angle measurements and scanning electron microscopy imaging, show that superhydrophobicity in the adhesive rose state was achieved using combinations of two differently sized particles, with an excess of the small 16 nm ones. Superhydrophobicity in the Lotus state was obtained when the filler concentration of 16 nm particles was 40 wt%, but under such conditions the coating was found to partially crack, which is detrimental in barrier applications. The preference for the rose wetting state can be explained by the round shape of the particles, which promotes the superhydrophobic rose wetting state over that of the superhydrophobic Lotus state.

  • 4.
    Ejenstam, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Corrosion protection by hydrophobic silica particle-polydimethylsiloxane composite coatings2015In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, no 99, p. 89-97Article in journal (Refereed)
    Abstract [en]

    In this study, the time-dependent corrosion protection ability of 10–15 µm thin polydimethylsiloxane -nanoparticle composite coatings was evaluated using mainly open circuit potential and electrochemical impedance spectroscopy measurements. The best result was obtained for the coating containing 20 wt% hydrophobic silica nanoparticles, where it was possible to achieve protection for almost 80 days in 3 wt% NaCl solution. The protective properties offered by this coating are suggested to be due to a synergistic effect of the hydrophobicity of the polydimethylsiloxane matrix and the prolonged diffusion path caused by addition of hydrophobic silica particles.

  • 5.
    Ejenstam, Lina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Tuominen, Mikko
    Haapanen, Janne
    Mäkelä, Jyrki M.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Long-term corrosion protection by a thin nano-composite coating2015In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584Article in journal (Refereed)
    Abstract [en]

    We report and discuss the corrosion protective properties of a thin nano-composite coating system consisting of an 11 μm thick polyester acrylate (PEA) basecoat, covered by an approximately 1 - 2 μm thick layer of TiO2 nanoparticles carrying a 0.05 μm thick hexamethyl disiloxane (HMDSO) top coat. The corrosion protective properties were evaluated on carbon steel substrates immersed in 3 wt% NaCl solution by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The protective properties of each layer, and of each pair of layers, were also evaluated to gain further understanding of the long term protective properties offered by the nano-composite coating. The full coating system showed excellent corrosion protective properties in the corrosive environment of 3 wt% NaCl-solution for an extended period of 100 days, during which the coating impedance, at the lower frequency limit (0.01 Hz), remained above 108 Ωcm2. We suggest that the excellent corrosion protective properties of the complete coating system is due to a combination of i) good adhesion and stability of the PEA basecoat, ii) the surface roughness and the elongated diffusion path provided by the addition of TiO2 nanoparticles, and iii) the low surface energy provided by the HMDSO top coat.

  • 6.
    Eriksson, Mimmi
    et al.
    RISE Res Inst Sweden, Stockholm, Sweden..
    Jarn, Mikael
    RISE Res Inst Sweden, Stockholm, Sweden..
    Tuominen, Mikko
    RISE Res Inst Sweden, Stockholm, Sweden..
    Wallqvist, Viveca
    RISE Res Inst Sweden, Stockholm, Sweden..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Stockholm, Sweden..
    Teisala, Hannu
    Max Planck Inst Polymer Res, Mainz, Germany..
    Vollmer, Doris
    Max Planck Inst Polymer Res, Mainz, Germany..
    Kappl, Michael
    Max Planck Inst Polymer Res, Mainz, Germany..
    Butt, Hans-Jurgen
    Max Planck Inst Polymer Res, Mainz, Germany..
    Gane, Patrick
    Omya Int AG, Oftringen, Switzerland. ; Aalto Univ, Espoo, Finland..
    Schoelkopf, Joachim
    Omya Int AG, Oftringen, Switzerland..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Stockholm, Sweden..
    Interactions at submerged liquid-repellent surfaces: Gas meniscus formation and development2019In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal (Other academic)
  • 7.
    Eriksson, Mimmi
    et al.
    RISE Res Inst Sweden, Biosci & Mat Surface, Proc & Formulat, SE-11486 Stockholm, Sweden.
    Tuominen, Mikko
    RISE Res Inst Sweden, Biosci & Mat Surface, Proc & Formulat, SE-11486 Stockholm, Sweden..
    Jarn, Mikael
    RISE Res Inst Sweden, Biosci & Mat Surface, Proc & Formulat, SE-11486 Stockholm, Sweden..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden, Bioscience and Materials − Surface, Process and Formulation, SE-114 86 Stockholm, Sweden.
    Wallqvist, Viveca
    RISE Res Inst Sweden, Biosci & Mat Surface, Proc & Formulat, SE-11486 Stockholm, Sweden..
    Butt, Hans Juergen
    Max Planck Inst Polymer Res, Dept Phys Interfaces, Ackermannweg 10, DE-55128 Mainz, Germany..
    Vollmer, Doris
    Max Planck Inst Polymer Res, Dept Phys Interfaces, Ackermannweg 10, DE-55128 Mainz, Germany..
    Kappl, Michael
    Max Planck Inst Polymer Res, Dept Phys Interfaces, Ackermannweg 10, DE-55128 Mainz, Germany..
    Schoelkopf, Joachim
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland..
    Gane, Patrick A. C.
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland.;Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, FI-00076 Aalto, Finland..
    Teisala, Hannu
    Max Planck Inst Polymer Res, Dept Phys Interfaces, Ackermannweg 10, DE-55128 Mainz, Germany..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Biosci & Mat Surface, Proc & Formulat, SE-11486 Stockholm, Sweden..
    Direct Observation of Gas Meniscus Formation on a Superhydrophobic Surface2019In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 13, no 2, p. 2246-2252Article in journal (Refereed)
    Abstract [en]

    The formation of a bridging gas meniscus via cavitation or nanobubbles is considered the most likely origin of the submicrometer long-range attractive forces measured between hydrophobic surfaces in aqueous solution. However, the dynamics of the formation and evolution of the gas meniscus is still under debate, in particular, in the presence of a thin air layer on a superhydrophobic surface. On superhydrophobic surfaces the range can even exceed 10 mu m. Here, we report microscopic images of the formation and growth of a gas meniscus during force measurements between a superhydrophobic surface and a hydrophobic microsphere immersed in water. This is achieved by combining laser scanning confocal microscopy and colloidal probe atomic force microscopy. The configuration allows determination of the volume and shape of the meniscus, together with direct calculation of the Young-Laplace capillary pressure. The long-range attractive interactions acting on separation are due to meniscus formation and volume growth as air is transported from the surface layer.

  • 8. Hansson, Petra M.
    et al.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Briscoe, Wuge H.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfaces2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 41, p. 17893-17902Article in journal (Refereed)
    Abstract [en]

    Friction forces have long been associated with the famous Amontons' rule that states that the friction force is linearly dependent on the applied normal load, with the proportionality constant being known as the friction coefficient. Amontons' rule is however purely phenomenological and does not in itself provide any information on why the friction coefficient is different for different material combinations. In this study, friction forces between a colloidal probe and nanostructured particle coated surfaces in an aqueous environment exhibiting different roughness length scales were measured by utilizing the atomic force microscope (AFM). The chemistry of the surfaces and the probe was varied between hydrophilic silica and hydrophobized silica. For hydrophilic silica surfaces, the friction coefficient was significantly higher for the particle coated surfaces than on the flat reference surface. All the particle coated surfaces exhibited similar friction coefficients, from which it may be concluded that the surface geometry, and not the roughness amplitude per se, influenced the measured friction. During measurements with hydrophobic surfaces, strong adhesive forces related to the formation of a bridging air cavity were evident from both normal force and friction force measurements. In contrast to the frictional forces between the hydrophilic surfaces, the friction coefficient for hydrophobic surfaces was found to depend on the surface structure and we believe that this dependence is related to the restricted movement of the three-phase line of the bridging air cavity. For measurements using a hydrophobic surface and a hydrophilic probe, the friction coefficient was significantly smaller compared to the two homogeneous systems. A layer of air or air bubbles on the hydrophobic surface working as a lubricating layer is a possible mechanism behind this observation.

  • 9.
    Hansson, Petra M
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Frictional forces between hydrophilic and hydrophobic particle coated nanostructured surfacesManuscript (preprint) (Other academic)
  • 10.
    Hansson, Petra M.
    et al.
    YKI, Ytkemiska Institutet AB.
    Hormozan, Yashar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Brandner, B. D.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, J.
    Gane, P. A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Effect of surface depressions on wetting and interactions between hydrophobic pore array surfaces2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 30, p. 11121-11130Article in journal (Refereed)
    Abstract [en]

    The surface structure is known to significantly affect the long-range capillary forces between hydrophobic surfaces in aqueous solutions. It is, however, not clear how small depressions in the surface will affect the interaction. To clarify this, we have used the AFM colloidal probe technique to measure interactions between hydrophobic microstructured pore array surfaces and a hydrophobic colloidal probe. The pore array surfaces were designed to display two different pore spacings, 1.4 and 4.0 ÎŒm, each with four different pore depths ranging from 0.2 to 12.0 ÎŒm. Water contact angles measured on the pore array surfaces are lower than expected from the Cassie-Baxter and Wenzel models and not affected by the pore depth. This suggests that the position of the three-phase contact line, and not the interactions underneath the droplet, determines the contact angle. Confocal Raman microscopy was used to investigate whether water penetrates into the pores. This is of importance for capillary forces where both the movement of the three-phase contact line and the situation at the solid/liquid interface influence the stability of bridging cavities. By analyzing the shape of the force curves, we distinguish whether the cavity between the probe and the surfaces was formed on a flat part of the surface or in close proximity to a pore. The pore depth and pore spacing were both found to statistically influence the distance at which cavities form as surfaces approach each other and the distance at which cavities rupture during retraction.

  • 11.
    Hansson, Petra M.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hormozan, Yashar
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Brandner, Birgit D.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Hydrophobic pore array surfaces: Wetting and interaction forces in water/ethanol mixtures2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 396, p. 278-286Article in journal (Refereed)
    Abstract [en]

    Interactions between and wetting behavior of structured hydrophobic surfaces using different concentrations of water/ethanol mixtures have been investigated. Silica surfaces consisting of pore arrays with different pore spacings and pore depths were made hydrophobic by silanization. Their static and dynamic contact angles were found to be independent of the pore depth while fewer pores on the surface, i.e. a closer resemblance to a flat surface, gave a lower contact angle. As expected, a higher amount of ethanol facilitated wetting on all the surfaces tested. Confocal Raman microscopy measurements proved both water and ethanol to penetrate into the pores. AFM colloidal probe force measurements clearly showed that formation of air cavitation was hindered between the hydrophobic surfaces in presence of ethanol, and an increase in ethanol concentration was followed by a smaller jump-in distance and a weaker adhesion force. On separation, an immediate jump-out of contact occurred. The measured forces were interpreted as being due to capillary condensation of ethanol between the surfaces giving rise to very unstable cavities immediately rupturing on surface separation.

  • 12. Hansson, Petra M.
    et al.
    Skedung, Lisa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Rutland, Mark W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Robust Hydrophobic Surfaces Displaying Different Surface Roughness Scales While Maintaining the Same Wettability2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 13, p. 8153-8159Article in journal (Refereed)
    Abstract [en]

    A range of surfaces coated with spherical silica particles, covering the size range from nanometer to micrometer, have been produced using Langmuir-Blodgett (LB) deposition. The particles were characterized both in suspension and in the Langmuir trough to optimize the surface preparation procedure. By limiting the particle aggregation and surface layer failures during the preparation steps, well-defined monolayers with a close-packed structure have been obtained for all particle sizes. Thus, this procedure led to structured surfaces with a characteristic variation in the amplitude and spatial roughness parameters. In order to obtain robust surfaces, a sintering protocol and an AFM-based wear test to determine the stability of the deposited surface layer were employed. Hydrophobization of the LB films followed by water contact angle measurements showed, for all tested particle sizes, the same increase in contact angle compared to the contact angle of a flat hydrophobic surface. This indicates nearly hexagonal packing and gives evidence for nearly, complete surface wetting of the surface features.

  • 13. Hansson, Petra M.
    et al.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Influence of Surface Topography on the Interactions between Nanostructured Hydrophobic Surfaces2012In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 21, p. 8026-8034Article in journal (Refereed)
    Abstract [en]

    Nanostructured particle coated surfaces, with hydrophobized particles arranged in close to hexagonal order and of specific diameters ranging from 30 nm up to 800 nm, were prepared by Langmuir-Blodgett deposition followed by silanization. These surfaces have been used to study interactions between hydrophobic surfaces and a hydrophobic probe using the AFM colloidal probe technique. The different particle coated surfaces exhibit similar water contact angles, independent of particle size, which facilitates studies of how the roughness length scale affects capillary forces (previously often referred to as "hydrophobic interactions") in aqueous solutions. For surfaces with smaller particles (diameter < 200 nm), an increase in roughness length scale is accompanied by a decrease in adhesion force and bubble rupture distance. It is suggested that this is caused by energy barriers that prevent the motion of the three-phase (vapor/liquid/solid) line over the surface features, which counteracts capillary growth. Some of the measured force curves display extremely long-range interaction behavior with rupture distances of several micrometers and capillary growth with an increase in volume during retraction. This is thought to be a consequence of nanobubbles resting on top of the surface features and an influx of air from the crevices between the particles on the surface.

  • 14.
    Koppolu, Rajesh
    et al.
    Abo Akad Univ, Lab Paper Coating & Converting, Ctr Funct Mat, SF-20500 Turku, Finland..
    Abitbol, Tiffany
    RISE Res Inst Sweden, Biosci & Mat Surface Proc & Formulat, S-11428 Stockholm, Sweden..
    Kumar, Vinay
    Abo Akad Univ, Lab Paper Coating & Converting, Ctr Funct Mat, SF-20500 Turku, Finland.;Finland Ltd, VTT Tech Res Ctr, High Performance Fiber Prod, Espoo 02044, Finland..
    Jaiswal, Aayush Kumar
    Abo Akad Univ, Lab Paper Coating & Converting, Ctr Funct Mat, SF-20500 Turku, Finland..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Biosci & Mat Surface Proc & Formulat, S-11428 Stockholm, Sweden..
    Toivakka, Martti
    Abo Akad Univ, Lab Paper Coating & Converting, Ctr Funct Mat, SF-20500 Turku, Finland..
    Continuous roll-to-roll coating of cellulose nanocrystals onto paperboard2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 10, p. 6055-6069Article in journal (Refereed)
    Abstract [en]

    There is an increased interest in the use of cellulose nanocrystal (CNC) films and coatings for a range of functional applications in the fields of material science, biomedical engineering, and pharmaceutical sciences. Most of these applications have been demonstrated on films and coatings produced using laboratory-scale batch processes, such as solvent casting, dip coating, or spin coating. For successful coating application of CNC suspensions using a high throughput process, several challenges need to be addressed: relatively high viscosity at low solids content, coating brittleness, and potentially poor adhesion to the substrate. This work aims to address these problems. The impact of plasticizer on suspension rheology, coating adhesion, and barrier properties was quantified, and the effect of different pre-coatings on the wettability and adhesion of CNC coatings to paperboard substrates was explored. CNC suspensions were coated onto pre-coated paperboard in a roll-to-roll process using a custom-built slot die. The addition of sorbitol reduced the brittleness of the CNC coatings, and a thin cationic starch pre-coating improved their adhesion to the paperboard. The final coat weight, dry coating thickness, and coating line speed were varied between 1-11 g/m(2), 900 nm-7 A mu m, and 2.5-10 m/min, respectively. The barrier properties, adhesive strength, coating coverage, and smoothness of the CNC coatings were characterized. SEM images show full coating coverage at coat weights as low as 1.5 g/m(2). With sorbitol as plasticizer and at coat weights above 3.5 g/m(2), heptane vapor and water vapor transmission rates were reduced by as much as 99% and 75% respectively. Compared to other film casting techniques, the process employed in this work deposits a relatively thick coating in significantly less time, and may therefore pave the way toward various functional applications based on CNCs. [GRAPHICS] .

  • 15.
    Koppolu, Rajesh
    et al.
    Abo Akad Univ, Ctr Funct Mat, Lab Paper Coating & Converting, SF-20500 Turku, Finland..
    Lahti, Johanna
    Tampere Univ Technol, Paper Converting & Packaging, Tampere 33100, Finland..
    Abitbol, Tiffany
    RISE Res Inst Sweden, Bioecon Biorefinery & Energy, S-11428 Stockholm, Sweden..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Kuusipalo, Jurkka
    Tampere Univ Technol, Paper Converting & Packaging, Tampere 33100, Finland..
    Toivakka, Martti
    Abo Akad Univ, Ctr Funct Mat, Lab Paper Coating & Converting, SF-20500 Turku, Finland..
    Continuous Processing of Nanocellulose and Polylactic Acid into Multilayer Barrier Coatings2019In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 12, p. 11920-11927Article in journal (Refereed)
    Abstract [en]

    Recent years have seen an increased interest toward utilizing biobased and biodegradable materials for barrier packaging applications. Most of the abovementioned materials usually have certain shortcomings that discourage their adoption as a preferred material of choice. Nanocellulose falls into such a category. It has excellent barrier against grease, mineral oils, and oxygen but poor tolerance against water vapor, which makes it unsuitable to be used at high humidity. In addition, nanocellulose suspensions' high viscosity and yield stress already at low solid content and poor adhesion to substrates create additional challenges for high-speed processing. Polylactic acid (PLA) is another potential candidate that has reasonably high tolerance against water vapor but rather a poor barrier against oxygen. The current work explores the possibility of combining both these materials into thin multilayer coatings onto a paperboard. A custom-built slot-die was used to coat either microfibrillated cellulose or cellulose nanocrystals onto a pigment-coated baseboard in a continuous process. These were subsequently coated with PLA using a pilot-scale extrusion coater. Low-density polyethylene was used as for reference extrusion coating. Cationic starch precoating and corona treatment improved the adhesion at nanocellulose/baseboard and nanocellulose/PLA interfaces, respectively. The water vapor transmission rate for nanocellulose + PLA coatings remained lower than that of the control PLA coating, even at a high relative humidity of 90% (38 degrees C). The multilayer coating had 98% lower oxygen transmission rate compared to just the PLA-coated baseboard, and the heptane vapor transmission rate reduced by 99% in comparison to the baseboard. The grease barrier for nanocellulose + PLA coatings increased 5-fold compared to nanocellulose alone and 2-fold compared to PLA alone. This approach of processing nanocellulose and PLA into multiple layers utilizing slot-die and extrusion coating in tandem has the potential to produce a barrier packaging paper that is both 100% biobased and biodegradable.

  • 16. Lindström, Tom
    et al.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    On The Mechanical and Chemical Factors Governing Retention and Formation of a Fine Paper Stock: The Case of Headbox Elongational Shear2015In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 5, no 4, p. 30-37Article in journal (Refereed)
    Abstract [en]

    The relation between formation and retention is of key importance in papermaking. This paper deals with how various variables (mix-to-wire speed difference, softwood/hardwood ratio, pulp consistency, headbox contraction, and various amounts of added two-component retention aid) affect the forming of paper and in turn retention and paper formation. The experiments were conducted using the EuroFEX paper machine at Innventia, which can be operated under steady-state conditions of the white water system. It was found that formation is worst when the mix-to-wire speed difference is close to zero or when the oriented shear is lowest. Retention, on the other hand, is to a large extent independent of mix-to-wire speed. Higher consistency during forming is generally associated with an enhanced susceptibility of fibres to flocculate, but a higher consistency in the headbox is, in this study, also associated with increased headbox contraction, which increases elongational shear. The higher the headbox consistency, the higher will be the first-pass retention because of the closer proximity of particles, which is beneficial for bridging flocculation. It is known that elongational shear is in general more beneficial to fibre dispersion than transverse shear and also that for weaker fibre flocs (higher hardwood pulp content), the effect of high headbox contraction (higher consistency) actually reverses the effect of consistency on sheet formation because elongational shear overcomes the effects of fibre crowding at high headbox consistency on sheet formation. In conclusion, we show how the effects of mix-to-wire speed difference, softwood/hardwood ratio, headbox consistency, headbox contraction, and amount of retention aid added (cationic polyacrylamide and colloidal silica) affect retention and formation of paper.

  • 17. MacKenzie, J.
    et al.
    Söderberg, D.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundell, F.
    Turbulent stress measurements with phase-contrast magnetic resonance through tilted slices2017In: Experiments in Fluids, ISSN 0723-4864, E-ISSN 1432-1114, Vol. 58, no 5, article id 51Article in journal (Refereed)
    Abstract [en]

    Aiming at turbulent measurements in opaque suspensions, a simplistic methodology for measuring the turbulent stresses with phase-contrast magnetic resonance velocimetry is described. The method relies on flow-compensated and flow-encoding protocols with the flow encoding gradient normal to the slice. The experimental data is compared with direct numerical simulations (DNS), both directly but also, more importantly, after spatial averaging of the DNS data that resembles the measurement and data treatment of the experimental data. The results show that the most important MRI data (streamwise velocity, streamwise variance and Reynolds shear stress) is reliable up to at least r¯ = 0.75 without any correction, paving the way for dearly needed turbulence and stress measurements in opaque suspensions.

  • 18.
    MacKenzie, Jordan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Söderberg, Daniel
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Research Institutes of Sweden.
    Lundell, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Centres, Wallenberg Wood Science Center.
    Turbulent stress measurements of fibre suspensions in a straight pipe2018In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 30, no 2, article id 025104Article in journal (Refereed)
    Abstract [en]

    The focus of the present work is an experimental study of the behaviour of semi-dilute, opaque fibre suspensions in fully developed cylindrical pipe flows. Measurements of the normal and turbulent shear stress components and the mean flow were acquired using phase-contrast magnetic resonance velocimetry. Two fibre types, namely, pulp fibre and nylon fibre, were considered in this work and are known to differ in elastic modulus. In total, three different mass concentrations and seven Reynolds numbers were tested to investigate the effects of fibre interactions during the transition from the plug flow to fully turbulent flow. It was found that in fully turbulent flows of nylon fibres, the normal, < u(z)u(z)>(+), and shear, < u(z)u(z)>(+) (note that <.> is the temporal average, u is the fluctuating velocity, z is the axial or streamwise component, and r is the radial direction), turbulent stresses increased with Reynolds number regardless of the crowding number (a concentration measure). For pulp fibre, the turbulent stresses increased with Reynolds number when a fibre plug was present in the flow and were spatially similar in magnitude when no fibre plug was present. Pressure spectra revealed that the stiff, nylon fibre reduced the energy in the inertial-subrange with an increasing Reynolds and crowding number, whereas the less stiff pulp fibre effectively cuts the energy cascade prematurely when the network was fully dispersed.

  • 19. Niga, P.
    et al.
    Hansson-Mille, P. M.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE – Research Institute of Sweden.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE – Research Institute of Sweden.
    Schoelkopf, J.
    Gane, P. A. C.
    Bergendal, Erik
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Tummino, A.
    Campbell, R. A.
    Johnson, C. Magnus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Interactions between model cell membranes and the neuroactive drug propofol2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 526, p. 230-243Article in journal (Refereed)
    Abstract [en]

    Vibrational sum frequency spectroscopy (VSFS) complemented by surface pressure isotherm and neutron reflectometry (NR) experiments were employed to investigate the interactions between propofol, a small amphiphilic molecule that currently is the most common general anaesthetic drug, and phospholipid monolayers. A series of biologically relevant saturated phospholipids of varying chain length from C18 to C14 were spread on either pure water or propofol (2,6-bis(1-methylethyl)phenol) solution in a Langmuir trough, and the change in the molecular structure of the film, induced by the interaction with propofol, was studied with respect to the surface pressure. The results from the surface pressure isotherm experiments revealed that propofol, as long as it remains at the interface, enhances the fluidity of the phospholipid monolayer. The VSF spectra demonstrate that for each phospholipid the amount of propofol in the monolayer region decreases with increasing surface pressure. Such squeeze out is in contrast to the enhanced interactions that can be exhibited by more complex amphiphilic molecules such as peptides. At surface pressures of 22–25 mN m−1, which are relevant for biological cell membranes, most of the propofol has been expelled from the monolayer, especially in the case of the C16 and C18 phospholipids that adopt a liquid condensed phase packing of its alkyl tails. At lower surface pressures of 5 mN m−1, the effect of propofol on the structure of the alkyl tails is enhanced when the phospholipids are present in a liquid expanded phase. Specifically, for the C16 phospholipid, NR data reveal that propofol is located exclusively in the head group region, which is rationalized in the context of previous studies. The results imply a non-homogeneous distribution of propofol in the plane of real cell membranes, which is an inference that requires urgent testing and may help to explain why such low concentration of the drug are required to induce general anaesthesia.

  • 20.
    Niga, Petru
    et al.
    RISE Res Inst Sweden Chem Mat & Surfaces, Box 5607, SE-11486 Stockholm, Sweden..
    Hansson-Mille, Petra M.
    RISE Res Inst Sweden Chem Mat & Surfaces, Box 5607, SE-11486 Stockholm, Sweden..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Schoelkopf, Joachim
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland..
    Gane, Patrick A. C.
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland.;Aalto Univ, Sch Chem Technol, Dept Bioprod & Biosyst, FI-00076 Helsinki, Finland..
    Dai, Jing
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Furo, Istvan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Campbell, Richard A.
    Inst Laue Langevin, 71 Ave Martyrs,CS20156, F-38042 Grenoble 9, France.;Univ Manchester, Div Pharm & Optometry, Manchester M13 9PT, Lancs, England..
    Johnson, C. Magnus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Propofol adsorption at the air/water interface: a combined vibrational sum frequency spectroscopy, nuclear magnetic resonance and neutron reflectometry study2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 1, p. 38-46Article in journal (Refereed)
    Abstract [en]

    Propofol is an amphiphilic small molecule that strongly influences the function of cell membranes, yet data regarding interfacial properties of propofol remain scarce. Here we consider propofol adsorption at the air/water interface as elucidated by means of vibrational sum frequency spectroscopy (VSFS), neutron reflectometry (NR), and surface tensiometry. VSFS data show that propofol adsorbed at the air/ water interface interacts with water strongly in terms of hydrogen bonding and weakly in the proximity of the hydrocarbon parts of the molecule. In the concentration range studied there is almost no change in the orientation adopted at the interface. Data from NR show that propofol forms a dense monolayer with a thickness of 8.4 angstrom and a limiting area per molecule of 40 angstrom(2), close to the value extracted from surface tensiometry. The possibility that islands or multilayers of propofol form at the air/water interface is therefore excluded as long as the solubility limit is not exceeded. Additionally, measurements of the 1H NMR chemical shifts demonstrate that propofol does not form dimers or multimers in bulk water up to the solubility limit.

  • 21.
    Oko, Asaf
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden.
    Martinez, D.Mark
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden.
    Infiltration and dimensional scaling of inkjet droplets on thick isotropic porous materials2014In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 17, no 2, p. 413-422Article in journal (Refereed)
    Abstract [en]

    We study the imbibition of picoliter (pL)-sized inkjet droplets on controlled pore glass membranes (CPG), as a suitable model for isotropic three-dimensional porous materials. We do so using a variety of liquids, i.e., water, formamide and diiodomethane, and measure the evolution of the imbibition process using high-speed digital imaging. Here, experiments were conducted on 2-280 nm CPG membranes with drops with initial volumes ranging from 100 to 600 pL. We derive scaling laws for imbibition through dimensional analysis and advance the argument that the rate of absorption is related to two-dimensionless groups where v(t) is the imbibed volume, as determined from experiments, t is the time, v (tot) the total liquid volume, the porosity, mu the liquid viscosity, k the permeability, and p (c) the Laplace capillary pressure. We show this scaling to well describe the system at intermediate T values and report that V alpha T-0.8.

  • 22.
    Oko, Asaf
    et al.
    SP Technical Research Institute of Sweden - Chemistry, Materials and Surfaces, Sweden .
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden - Chemistry, Materials and Surfaces, Sweden .
    Brandner, Birgit D.
    Bugner, Douglas
    Cook, Wayne
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden - Chemistry, Materials and Surfaces, Sweden .
    Aggregation of inkjet ink components by Ca and Mg ions in relation to colorant pigment distribution in paper2014In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 456, p. 92-99Article in journal (Refereed)
    Abstract [en]

    Papers coated with salts containing divalent cations exhibit superior inkjet print quality, which has been suggested to be due to fast aggregation of the colorant pigments close to, or even on, the surface of the paper. In this work we show the pivotal role of the carboxylic acid containing dispersing polymer. We report a series of aggregation and sedimentation experiments with commercial inks, generic ink formulations and specific ingredients comprising these formulations, and find differences in their response to the presence of MgCl2 or CaCl2. In particular, flocs and sediments formed in the presence of MgCl2 are denser than those formed in the presence of CaCl2. These differences are not predicted by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. We suggest that ion specific interactions occurring between Mg2+ or Ca2+, and charged carboxylate groups residing on the dispersing polymers, provoke the observed behavior.

  • 23.
    Oko, Asaf
    et al.
    YKI, Inst Surface Chem, Ytkemiska Inst AB.
    Swerin, Agne
    YKI, Inst Surface Chem, Ytkemiska Inst AB.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Imbibition and Evaporation of Water Droplets on Paper and Solid Substrates2011In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 55, no 1, p. 010201-Article in journal (Refereed)
    Abstract [en]

    Imbibition and evaporation of picoliter (pL) sized water droplets on paper media commonly used for inkjet printing is measured using high speed imaging system. Three types of uncoated and coated paper samples were chosen: multipurpose uncoated paper (80 g/m(2)), matte coated paper (230 g/m2), and gloss coated paper (240 g/m(2)). As a reference, the rate of the evaporation process was quantified by using three impermeable solid substrates with different wetting characteristics, i.e., silicon, glass, and hydrophobized glass. It is shown that for water droplets of about 60 pL, imbibition is the dominant phenomenon on the matte and gloss coated paper leading to a total drying time (imbibition plus evaporation) of 10-15 ms for gloss coated paper and 30-150 ms on the matte coated paper. In the latter sample, different regimes in the imbibition process were correlated with the layered structure of the sample. The drying process on the multipurpose paper is dominated by evaporation, with initial drying rate of 0.4-0.6 pL/ms.

  • 24.
    Oko, Asaf
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden.
    Niga, Petru
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden .
    Infiltration and dimensional scaling of inkjet droplets onpapers with different surface chemistryManuscript (preprint) (Other academic)
    Abstract [en]

    We investigate experimentally and theoretically the spontaneous imbibition of complex inkjet formulations utilizing paper capillary rise and imbibition of inkjet drops. We compare two commercially available papers of the same structure but with different chemistry, one of them surface treated with CaCl. This additive is known to improve print quality when water based pigmented inkjet inks are used by rapidly aggregating the colorant pigments close to, or even on, the surface of the paper. In a previous publication we showed that the key components in the destabilization mechanism of the ink are the dispersing polymers that contain carboxylate groups which interact specifically with the Ca2+ cation. Here we demonstrate the impact of this destabilization effect on the spontaneous imbibition of ink formulations comprised of these polymers, and find that on large scale and long time the imbibition rate is slower in the CaCl2 containing paper compare to the CaCl2 free paper, as shown in paper capillary rise experiments, but on a much smaller scale and shorter times relevant for single inkjet drops no significant differences are observed. We approximate the paper structure to a two dimensional anisotropic porous material, and using Darcy’s law as a base derive dimensionless groups that scale drop imbibition.. This derivation is an expansion of the previously published dimensional scaling of drop imbibition on thick isotropic porous material. We obtain the average global system properties required, by performing sets of drop imbibition experiments where drops are impinged on random paper locations, and use the results to calculate the average volume loss of a single imbibing drop. This averageing procedure is then used in the dimensional scaling.

  • 25. Reverdy, C.
    et al.
    Belgacem, N.
    Moghaddam, M. S.
    Sundin, M.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology. RISE Research Institutes of Sweden – Bioscience and Materials, Box 5607, Stockholm, Sweden.
    Bras, J.
    One-step superhydrophobic coating using hydrophobized cellulose nanofibrils2018In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 544, p. 152-158Article in journal (Refereed)
    Abstract [en]

    Superhydrophobic surfaces have high potential in self-cleaning and anti-fouling applications. We developed a one-step superhydrophobic coating formulation containing sodium oleate (NaOl), hydrophobized precipitated calcium carbonate and biobased cellulose nanofibrils (CNFs) hydrophobized with either alkyl ketene dimer (AKD) or amino propyl trimethoxy silane (APMS) as a binder to fix and distribute the particles. Coatings were made on paperboard and the wetting behavior of the surface was assessed. Static, advancing and receding contact angles with water as well as roll-off and water shedding angle were compared to coatings made with styrene butadiene latex as binder instead of CNFs. Modifications with alkyl ketene dimer showed most promising results for a viable process in achieving superhydrophobic paperboard but required reformulation of the coating with optimized and reduced amount of NaOl to avoid surfactant-induced wetting via excess NaOl. A static water contact angle of 150° was reached for the CNF-AKD. The use of CNFs enables the improvement of coating quality avoiding cracking with the use of nanocellulose as a renewable binder.

  • 26. Sedighi Moghaddam, M.
    et al.
    Wålinder, Magnus. E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Multicycle wilhelmy plate method for wetting properties, swelling and liquid sorption of wood2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 39, p. 12145-12153Article in journal (Refereed)
    Abstract [en]

    A multicycle Wilhelmy plate method has been developed to investigate wetting properties, liquid sorption, and swelling of porous substrates such as wood. The use of the method is exemplified by studies of wood veneers of Scots pine sapwood and heartwood, which were subjected to repeated immersion and withdrawal in a swelling liquid (water) and in a nonswelling liquid (octane). The swelling liquid changes the sample dimensions during measurements, in particular its perimeter. This, in turn, influences the force registered. A model based on a linear combination of the measured force and final change in sample perimeter is suggested, and validated to elucidate the dynamic perimeter change of wood veneer samples. We show that pine heartwood and pine sapwood differ in several respects in their interaction with water. Pine heartwood showed (i) lower liquid uptake, (ii) lower swelling, (iii) higher contact angle, and (iv) lower level of dissolution of surface active components (extractives) than pine sapwood. We conclude that the method is also suitable for studying wetting properties of other porous and swellable materials. The wettability results were supported by surface chemical analysis using X-ray photoelectron spectroscopy, showing higher extractives and lignin content on heartwood than on sapwood surfaces.

  • 27.
    Sedighi Moghaddam, Maziar
    et al.
    SP Tech Res Inst Sweden, S-11486 Stockholm, Sweden.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wålinder, Magnus E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wettability and liquid sorption of wood investigated by Wilhelmy plate method2014In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 48, no 1, p. 161-176Article in journal (Refereed)
    Abstract [en]

    The wettability of Scots pine veneers was investigated with different approaches using the Wilhelmy plate method. The probe liquids were water and octane, which differ; in that, water is able to swell the wood sample, whereas octane does not. Novel approaches based on the Wilhelmy plate method to study wettability, liquid penetration, and swelling behavior of wood veneers are introduced. First, immersion to constant depth was performed, and liquid uptake with time was evaluated. Different kinetic regimes, the fastest one associated with contact angle changes and the slowest regime associated with liquid sorption by capillary and diffusion, were observed. Two other approaches, imbibition at constant depth (with initial deeper immersion) and full immersion, were utilized in order to keep the contact angle constant during measurements. Dynamic wettability studies were done by a multi-cycle (10-20 cycles) Wilhelmy method. Based on this, the time-dependent swelling of wood and changes in sample perimeter could be obtained. Generally, water showed higher absorption than octane. In all wettability studies, and for both probe liquids, the penetration process starts with a fast initial sorption, which is followed by swelling in the case of water.

  • 28.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Heydarihamedani, Golrokh
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tuominen, Mikko
    SP Technical Research Institute of Sweden.
    Fielden, Matthew
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Haapanen, Janne
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Mäkelä, Jyrki M.
    TUT Tampere University of Technology, Aerosol Physics Laboratory, Department of Physics.
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Hydrophobisation of wood surfaces by combining liquid flame spray (LFS)and plasma treatment: dynamic wetting properties2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 6, p. 527-537Article in journal (Refereed)
    Abstract [en]

    The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate method, resulting in advancing and receding contact angles as well as sorption behaviour of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and Xray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behaviour. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

  • 29.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Van den Bulcke, Jan
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Calessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Van Acker, Joris
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Microstructure of chemically modified wood using X-ray computedtomography scanning in relation to wetting propertiesManuscript (preprint) (Other academic)
    Abstract [en]

    X-ray computed tomography was utilized to visualize and quantify the 2D and 3D microstructure of acetylated and furfurylated southern yellow pine (SYP) and maple samples. The total porosity and the porosity of different anatomical components, the cell wall thickness and the maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. Our data show significant changes in the wood structure for furfurylated sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for acetylated samples at the resolution of the measurement (0.8 μm). The images obtained for furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibres largely remained unchanged. Furfurylation significantly decreased the porosity of the sample, and this was observed in both earlywood and latewood regions in southern yellow pine softwood samples. In contrast, the total porosity of this softwood sample was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Cell wall thickness measurements revealed a significant increase after chemical modification especially at higher levels of furfurylation.

  • 30.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials. SP Tech Res Inst Sweden Chem Mat & Surfaces, Sweden.
    Van den Bulcke, Jan
    Wålinder, Magnus E. P.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Van Acker, Joris
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Microstructure of chemically modified wood using X-ray computed tomography in relation to wetting properties2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 2, p. 119-128Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (XCT) was utilized to visualize and quantify the 2D and 3D microstructure of acetylated southern yellow pine (pine) and maple, as well as furfurylated pine samples. The total porosity and the porosity of different cell types, as well as cell wall thickness and maximum opening of tracheid lumens were evaluated. The wetting properties (swelling and capillary uptake) were related to these microstructural characteristics. The data show significant changes in the wood structure for furfurylated pine sapwood samples, including a change in tracheid shape and filling of tracheids by furan polymer. In contrast, no such changes were noted for the acetylated pine samples at the high resolution of 0.8 mu m. The XCT images obtained for the furfurylated maple samples demonstrated that all ray cells and some vessel elements were filled with furan polymer while the fibers largely remained unchanged. Furfurylation significantly decreased the total porosity of both the maple and pine samples. Furthermore, this was observed in both earlywood (EW) and latewood (LW) regions in the pine samples. In contrast, the total porosity of pine samples was hardly affected by acetylation. These findings are in line with wetting results demonstrating that furfurylation reduces both swelling and capillary uptake in contrast to acetylation which reduces mostly swelling. Furfurylation significantly increased the cell wall thickness of both the maple and pine samples, especially at higher levels of furfurylation.

  • 31.
    Sedighi Moghaddam, Maziar
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Wålinder, E.P. Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Calessson, M. Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden.
    Wettability and swelling of acetylated and furfurylated wood analyzed by multicycle Wilhelmy plate method2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 1, p. 69-77Article in journal (Refereed)
    Abstract [en]

    The wetting, dimensional stability and sorption properties of a range of modified wood samples obtained either by acetylation or furfurylation were compared with those of unmodified samples of the same wood species via a multicycle Wilhelmy plate method. Wettability measurements were performed with water and octane as the swelling and non-swelling liquids, respectively. It was found that acetylation reduces water uptake mainly by reducing the swelling. In comparison, furfurylation reduces both swelling and the void volume in the sample. To quantify the effect of the modification process of the wood properties, the parameters “liquid up-take reduction” and the “perimeter change reduction” were introduced, which were determined from multicycle Wilhelmy plate measurements. Compared with the acetylated wood, the furfurylated wood with a higher level of weight percent gain exhibited larger property changes on the surface and in terms of swelling and sorption properties.

  • 32.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Tech Res Inst Sweden, Biosci & Mat Surface Proc & Formulat, SE-11486 Stockholm, Sweden.
    Dimensional Scaling of Aqueous Ink Imbibition and Inkjet Printability on Porous Pigment Coated Paper-A Revisit2018In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 57, no 49, p. 16684-16691Article in journal (Refereed)
    Abstract [en]

    A recently published dimensional scaling of infiltration of water-based inkjet fluids was used to revisit published inkjet printability data on mineral-pigment-based, inkjet-receptive coated papers. The dimensional scaling was developed using simple fluids on homogeneous isotropic media and applied on uncoated papers using complex inkjet fluids but so far has not been related to printability. It is shown that the scaling can also work for coated papers using commercial dye- and pigment-based inks with a suggested relation to printability as given by the color gamut area, in which the primary factor is the product of permeability and capillary pressure. A successful scaling suggests that inkjet printability can be predicted from flow and materials parameters, namely, porosity, viscosity, imbibed volume, permeability, and capillary pressure, and would be of general applicability in other areas of inkjet printing. The results further imply the usefulness of the approach in other functional surface modification using waterborne procedures on hard or soft porous materials.

  • 33.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Probing interactions of nanocellulose and sugars using rheology2017In: International Conference on Nanotechnology for Renewable Materials 2017, TAPPI Press , 2017, p. 305-314Conference paper (Refereed)
  • 34.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Biosci & Mat, Stockholm, Sweden..
    Super liquid repellent surfaces - non-wetting forces, cavity growth and coatings on biobased materials2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal (Other academic)
  • 35.
    Swerin, Agne
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Brandner, B. D.
    Interaction in cellulosic fiber-fiber joints at humid and wet conditions by AFM and confocal Raman microscopy2018In: International Conference on Nanotechnology for Renewable Materials 2018, TAPPI Press , 2018, p. 64-73Conference paper (Refereed)
    Abstract [en]

    Interactions in fiber-fiber joints: • Interaction in crossed cellulosic fiber joints between was studied by atomic force colloidal probe microscopy (AFM) and mapping of surfaces and bonding sites using confocal Raman microspectroscopy (CRM) • CRM imaged surfaces and joints on thermomechanical pulp fibers, bleached pulp fibers and rayon fibers • Chemical and structural constituents relevant for bonding at high enough resolution can be imaged • Differences due to stresses or strains at, or close to, the fiber-fiber bonded area was detected but could not be evaluated. • Clean rayon fibers and bleached kraft pulp fibers, attached to an AFM cantilever and to the edge of an AFM chip, were brought in contact in a 90° crossed configuration • Forces measured in humid air and in water during approach and during retract • Bleached kraft pulp fiber-fiber joints can measured combined in adhesion and friction • Rayon fibers at different RH's give influence of capillary attraction at cross-points. Adhesion values significantly less than predicted by capillary attraction, due to roughness. 

  • 36.
    Swerin, Agne
    et al.
    YKI, Institute for Surface Chemistry, Sweden.
    Brandner, Birgitt
    Wallqvist, Vivica
    Wåhlander, Martin
    YKI, Institute for Surface Chemistry, Sweden.
    Probing molecular, nanoscale and adhesive forces related to fiber-fiber bonding and optimized surface interactions2009In: International Conference on Nanotechnology for the Forest Products Industry 2009, Edmonton Canada, 2009, Vol. 1, p. 229-283Conference paper (Refereed)
  • 37.
    Swerin, Agne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Mira, I.
    Ink-jettable paper-based sensor for charged macromolecules and surfactants2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, p. 389-395Article in journal (Refereed)
    Abstract [en]

    The use of metachromatic dye-based formulations for the preparation of inkjettable prototype indicators suitable for the detection of charged macromolecules, surfactants or other low molecular weight molecules was investigated. Such indicators were based on the use of metachromatic o-toluidine blue (OTB) that undergoes a characteristic change in color (from blue to pink) upon interaction with anionic macromolecules. When applied onto absorbing substrates such as paper and paperboard, solutions containing OTB and the same dye in the presence of potassium polyvinyl sulfate (KPVS), proved to indicate negatively charged polymers and cationic surfactants. The colorimetric responses suggest a detection limit and sensitivity both are in the order of 1 mM of charged species but can be further improved. Interactions between active species in the indicators and some of the additives in inkjettable formulations (surfactant and humectants) interfered with the mechanism by which an OTB/KVPS-based system work only to a minor degree and could be overcome by priming the substrate. An OTB-based system was formulated into an inkjettable formulation that, once applied to a substrate, was showed to indicate charged polymers and surfactants. This concept has the potential for sensing/indication of other charged macromolecules, such as carboxylates and polyphosphates, which are relevant in biomedical (e.g. fouling due to microbial activity), packaging applications (e.g. migration or release of compounds, food spoilage), microfluidic devices or a simple dipstick application to indicate the presence of charged components.

  • 38.
    Swerin, Agne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Sundin, Mikael
    Wåhlander, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Formulation of superhydrophobic pigment coatings2015In: Formulation of superhydrophobic pigment coatings, TAPPI Press, 2015, Vol. 2, p. 1410-1424Conference paper (Refereed)
  • 39.
    Swerin, Agne
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden-Chemistry, Materials and Surfaces, Sweden.
    Sundin, Mikael
    Wåhlander, Martin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    One-pot waterborne superhydrophobic pigment coatings at high solids with improved scratch and water resistance2016In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 495, p. 79-86Article in journal (Refereed)
    Abstract [en]

    A pigment coating was developed to achieve superhydrophobicity in one step from a waterborne formulation containing aragonite calcium carbonate, hydrophobized using sodium oleate, latex binder and cross -linker. Coatings formulated <= 50 mass% and applied to polyethylene coated paperboard substrates displayed typical superhydrophobic features: water contact angles >= 150 degrees, low roll-off angle and low stain sizes, but poor scratch and water resistance as well as foaming issues during preparation. Reformulation at higher solids content significantly improved scratch and water resistance properties. Water rinsing of the dried coatings further increased the water barrier capacity due to reduced surfactant-assisted wetting; findings were corroborated by detailed surface chemistry analyses showing the removal of surface-active components after water rinsing of the dried coatings. A plausible cause for the improved durability is the fact that capillary forces increase exponentially with increasing pigment volume fraction (power law exponent of 2.2) leading to efficient binder coverage during the early stage of pigment coating consolidation.

  • 40. Tuominen, Mikko
    et al.
    Teisala, Hannu
    Haapanen, Janne
    Makela, Jyrki M.
    Honkanen, Mari
    Vippola, Minnamari
    Bardage, Stig
    Walinder, Magnus E. P.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Superamphiphobic overhang structured coating on a biobased material2016In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 389, p. 135-143Article in journal (Refereed)
    Abstract [en]

    A superamphiphobic coating on a biobased material shows extreme liquid repellency with static contact angles (CA) greater than 150 degrees and roll-off angles less than 10 degrees against water, ethylene glycol, diiodomethane and olive oil, and a CA for hexadecane greater than 130 degrees. The coating consisting of titanic nanoparticles deposited by liquid flame spray (LFS) and hydrophobized using plasma-polymerized perfluorohexane was applied to a birch hardwood. Scanning electron microscopy (SEM) imaging after sample preparation by UV laser ablation of coated areas revealed that capped structures were formed and this, together with the geometrically homogeneous wood structure, fulfilled the criteria for overhang structures to occur. The coating showed high hydrophobic durability by still being non-wetted after 500 000 water drop impacts, and this is discussed in relation to geometrical factors and wetting forces. The coating was semi-transparent with no significant coloration. A self-cleaning effect was demonstrated with both water and oil droplets. A self-cleanable, durable and highly transparent superamphiphobic coating based on a capped overhang structure has a great potential for commercial feasibility in a variety of applications, here exemplified for a biobased material.

  • 41. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Swerin, Agne
    Ostlund, Catherine
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Influence of Surface Topography on Adhesive and Long-Range Capillary Forces between Hydrophobic Surfaces in Water2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 16, p. 9197-9207Article in journal (Refereed)
    Abstract [en]

    We report oil the interactions between a hydrophobic probe particle and surfaces with nanoscopic surface features, These surfaces have been prepared by spin-coating of nanoparticles and by polishing. The surface topography was characterized by AFM, using the methods of high-resolution imaging, low-resolution imaging using the probe particle, and by the rolling ball method. The spin-coated surfaces can be characterized as nanostructured due to the high density of nanoparticles that oil a short length scale provides a regular pattern of crevices and hills. Oil these surfaces a larger waviness is also distinguished. In contrast, the polished surfaces display sharp nanoscopic peaks and hardly any crevices. I n all cases the dominant force at short separations was found to be a capillary attraction due to the formation of an air/ vapor condensate. Our data show that the large-scale waviness of the surface does not significantly influence the range and magnitude of the capillary attraction, but large local variations in these quantities are found. The large variation in on force corresponds to a small variation in local contact angle of the capillary condensate It the surfaces. The adhesion report discusses how the nature of the surface topographical features influences the capillary attraction by influencing the local contact angle and by pinning of the three-phase contact line. The effect is clearly dependent on whether the surface features exist in the form of crevices or as extending ridges.

  • 42. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Swerin, Agne.
    Schoelkopf, J.
    Gane, P. A. C.
    Interaction forces between talc and hydrophobic particles probed by AFM2006In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 277, no 03-jan, p. 183-190Article in journal (Refereed)
    Abstract [en]

    The interaction between cleaved talc surfaces and hydrophobic probe particles, silanized silica and thiolized gold, has been investigated employing the atomic force microscopy (AFM) colloidal probe technique. These model systems have hydrophobicities similar to some of the talc-pitch combinations present during pulp and paper manufacture. The talc surfaces used in this study, in the [0 0 1] plane, show a micro-roughness with sharp peaks of up to 3 nm in height. The force profiles obtained demonstrate the predominance of a long-range attractive force. However, the range and magnitude of the attractive force show large variability. The variability of the attractive force, and the frequent observations of clear steps in the force curve demonstrate that it is caused by gas/vapor cavities bridging the Surfaces once the surfaces are brought sufficiently close together. The results suggest that the same mechanism is of importance in applications where talc is used as a collector for pitch.

  • 43. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Swerin, Agne
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Influence of Wetting and Dispersing Agents on the Interaction between Talc and Hydrophobic Particles2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 12, p. 6909-6915Article in journal (Refereed)
    Abstract [en]

    The interactions between a natural talc surface and a model hydrophobic particle have been investigated in aqueous solutions by employing the atomic force microscopy (AFM) colloidal probe technique. The results demonstrate the presence of long-range attractive forces due to bridging via preadsorbed or induced bubbles/cavities. Due to the natural heterogeneity of talc, and the stochastic nature of the bubble bridging process, the variability in the range and magnitude of the attraction is larger than that for cases when other interactions predominate or than that when only model surfaces are used. Addition of poly(acrylic acid), a common dispersing agent, did not affect the measured forces. Thus, we conclude that poly(acrylic acid) does not adsorb to the basal plane of talc. In sharp contrast, addition of Pluronic PE6400, a nonionic triblock polymer used as wetting agent, resulted in complete removal of the bubble-induced attractive force. Instead, a short-range steric repulsion is the dominating feature. Clearly, Pluronic PE6400 is able to displace air bubbles from the surface and prevent their formation when the particles come into contact. These are suggested to be important features of efficient wetting agents.

  • 44. Wallqvist, Viveca
    et al.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Swerin, Agne
    Schoelkopf, Joachim
    Gane, Patrick A. C.
    Interaction forces between talc and pitch probed by atomic force microscopy2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 8, p. 4248-4256Article in journal (Refereed)
    Abstract [en]

    Colloidal wood resin components present in pulp are collectively called pitch. The presence of pitch may cause severe problems due to deposits in and on the paper machine. There is thus a need for controlling pitch aggregation and adsorption. To be able to develop more efficient pitch control systems, one needs to develop the understanding of pitch-pitch interactions and of the interactions between pitch and other materials. With this general goal in mind, we present methods for preparing geometrically well-defined pitch particles attached to atomic force microscopy tips. This has enabled us to investigate the interactions between pitch and talc, an additive commonly used for pitch control. We have used model pitch particles consisting of one component only (abietic acid), a mixture of components (collophonium), and particles prepared from real pitch deposits. We show that the forces acting between pitch and talc are attractive and, once the initial approach is made, exert this attraction out to large distances of separation. We present evidence that the formation of bridging air bubbles or cavities is responsible for this interaction.

  • 45.
    Wallqvist, Viveca
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bergström, Lennart
    Arwin, H.
    Hamaker constants for talc minerals using spectral ellipsometric dataManuscript (preprint) (Other academic)
    Abstract [en]

    Measurements of refractive indices over a large wavelength span for talc minerals using spectral ellipsometry allow more accurate determinations of Hamaker constants than previously reported, or otherwise calculated from literature data. We report that for the birefringent talc minerals different Hamaker constants are obtained for samples cut in different crystallographic orientations. In water, very small differences, from 1.710-20 to 1.910-20 J is obtained for nanocrystalline talc samples cut in different directions, whereas a microcrystalline sample from another source give considerably higher value of the Hamaker constant, 4.210-20J. The difference is explained by a significant difference in the refractive index. Implications for interactions relevant in connection to the use of talc as a pitch control agent, in the action of wetting and dispersing additives used as processing aids, and in combinations of talc with cellulose, calcite and polystyrene are indicated.

  • 46.
    Wallqvist, Viveca
    et al.
    YKI, Ytkemiska Institutet AB, Institute for Surface Chemistry, Stockholm, Sweden .
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry (closed 20081231).
    Swerin, Agne
    YKI, Ytkemiska Institutet AB, Institute for Surface Chemistry, Stockholm, Sweden .
    Gane, P.A.C.
    Ridgeway, C.
    Schoelkopf, J.
    Fluid transport in compacted porous talc blocks2008In: Fluid Dynamics & Materials Processing, ISSN 1555-256X, E-ISSN 1555-2578, ISSN 1555-256X, Vol. 4, no 2, p. 85-98Article in journal (Refereed)
    Abstract [en]

    It has been shown that talc powder can be compacted into tablets with a preferred orientation of the platelets. The tablets can be obtained with different controlled porosity depending on pressing methods and applied pressure. The tablets can be obtained with or without additives, which may, in turn, be adsorbed. The orientation of the high aspect ratio platy talc, the surface chemistry imparted by the additives and the transported fluid influence the imbibition and permeation rates. Non-polar hexadecane displays a higher imbibition and permeability than water for all particulate orientations during short timescale absorption, likely due to the oleophilic nature of talc, and thus a more complete filling of the pores for non-polar liquids is to be expected. At longer timescales water is imbibed either at a similar rate to hexadecane or faster depending on the surface chemistry generated by additives leading to hydrophilicity. The swelling of the added polymers used to create wettability leads to break-up of the structure and exposure of hydrophilic surfaces for more rapid imbibition. It is not possible, therefore, to measure reliably the water uptake parameters when talc is fully dispersed with surfactants. Furthermore, dispersing agents tend to contribute to the blocking of pores and throats in the swollen state, and so a limitation in total imbibed volume occurs. The permeability under pressure is also inhibited by additives, which supports the suggestion of partial blockage of the pores and throats. When the individual talc crystal c axes, defining the perpendicular to the [001] planes, are oriented 90° to the primary average liquid flow direction, i.e. are oriented in a planar configuration to the flow, imbibition and permeation of wetting liquid are increased. This is assumed to be due to decreased tortuosity, provided the liquid is wetting in respect to the oriented edge surface. However, non-wetting liquids in respect to all, or geometrically dependent, orientations are subject also to the surface chemistry presented by the orientation, i.e. whether the talc is primarily displaying OH-groups or not, or adsorbed species aiding wetting by the liquid. Measurements where additives are not strongly adsorbed are complicated by the solubility of some wetting and dispersing agents.

  • 47.
    Wojas, Natalia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Biosci & Mat, Stockholm, Sweden..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden.
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Biosci & Mat, Stockholm, Sweden.;KTH Royal Inst Technol, CHE Surface & Corros Sci, Stockholm, Sweden..
    Wallqvist, Viveca
    RISE Res Inst Sweden, Biosci & Mat, Stockholm, Sweden..
    Jarn, Mikael
    RISE Res Inst Sweden, Biosci & Mat, Stockholm, Sweden..
    Gane, Patrick
    Omya Int AG, Oftringen, Switzerland..
    Schoelkopf, Joachim
    Omya Int AG, Oftringen, Switzerland..
    Adam, Marcus
    Omya Int AG, Oftringen, Switzerland..
    Adsorption of water and gaseous species on calcite surfaces at different relative humidity and temperature2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal (Other academic)
  • 48.
    Wojas, Natalia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Div Biosci & Mat Surface Proc & Formulat, Box 5607, SE-11486 Stockholm, Sweden.
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Div Biosci & Mat Surface Proc & Formulat, Box 5607, SE-11486 Stockholm, Sweden.
    Wallqvist, Viveca
    RISE Res Inst Sweden, Div Biosci & Mat Surface Proc & Formulat, Box 5607, SE-11486 Stockholm, Sweden..
    Jarn, Mikael
    RISE Res Inst Sweden, Div Biosci & Mat Surface Proc & Formulat, Box 5607, SE-11486 Stockholm, Sweden..
    Schoelkop, Joachim
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland..
    Gane, Patrick A. C.
    Omya Int AG, Baslerstr 42, CH-4665 Oftringen, Switzerland.;Aalto Univ, Sch Chem Engn, Dept Bioprod & Biosyst, POB 16300, FI-00076 Aalto, Finland..
    Claesson, Per M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Res Inst Sweden, Div Biosci & Mat Surface Proc & Formulat, Box 5607, SE-11486 Stockholm, Sweden.
    Iceland spar calcite: Humidity and time effects on surface properties and their reversibility2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 541, p. 42-55Article in journal (Refereed)
    Abstract [en]

    Understanding the complex and dynamic nature of calcite surfaces under ambient conditions is important for optimizing industrial applications. It is essential to identify processes, their reversibility, and the relevant properties of CaCO3 solid-liquid and solid-gas interfaces under different environmental conditions, such as at increased relative humidity (RH). This work elucidates changes in surface properties on freshly cleaved calcite (topography, wettability and surface forces) as a function of time (<= 28 h) at controlled humidity (<= 3-95 %RH) and temperature (25.5 degrees C), evaluated with atomic force microscopy (AFM) and contact angle techniques. In the presence of humidity, the wettability decreased, liquid water capillary forces dominated over van der Waals forces, and surface domains, such as hillocks, height about 7.0 angstrom, and trenches, depth about -3.5 angstrom, appeared and grew primarily in lateral dimensions. Hillocks demonstrated lower adhesion and higher deformation in AFM experiments. We propose that the growing surface domains were formed by ion dissolution and diffusion followed by formation of hydrated salt of CaCO3. Upon drying, the height of the hillocks decreased by about 50% suggesting their alteration into dehydrated or less hydrated CaCO3. However, the process was not entirely reversible and crystallization of new domains continued at a reduced rate.

  • 49.
    Wärnheim, Alexander
    et al.
    KTH. RISE Biosci & Mat, Stockholm, Sweden..
    Toprak, Muhammet
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ahniyaz, Anwar
    RISE Biosci & Mat, Stockholm, Sweden..
    Swerin, Agne
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. RISE Biosci & Mat, Stockholm, Sweden..
    Abitbol, Tiffany
    RISE Bioecon, Stockholm, Sweden..
    Nanocellulose-based hybrid materials for optical applications2019In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal (Other academic)
  • 50.
    Wåhlander, Martin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hansson-Mille, P. M.
    Swerin, Agne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Superhydrophobicity: Cavity growth and wetting transition2015In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 448, p. 482-491Article in journal (Refereed)
    Abstract [en]

    We show by using AFM colloidal probe microscopy (combinations of hydrophobic/superhydrophobic as probe/surface) that superhydrophobicity displays a set of specific events when compared with hydrophobicity. Both attraction (due to capillary and wetting forces) and repulsion (most likely due to repelling air/vapor layers or micro-/nanobubbles) occur upon approach and when surfaces are pulled apart both shorter range (50-100. nm or more) and longer range (several micrometers) attractive forces are displayed. The interaction is explained by forces generated through the formation of air and water vapor cavities, in the shorter-range (<50. nm) case maintaining a constant volume of the cavity, in agreement with calculation of capillary forces, and in the longer-range (<1. μm) case through access of air to the cavity, in agreement with thermodynamics of cavity growth. An added sodium dodecyl sulphate surfactant gave a partially reversible wetting transition and reduced the longer-range interaction to shorter-range, suggesting a transfer from the Cassie-Baxter to the Wenzel wetting regime. The findings would be of interest in development of practical applications, such as for anti-soiling, anti-icing, protection of electrical components and for extreme water-repellency in paper and textiles.

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