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  • 51. Back, EL
    et al.
    Laudi, B
    Elftonson, J
    YKI – Ytkemiska institutet.
    Effect of modifiers on wax properties and on dispersibility under hot alkaline conditions1995Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 10, s. 122-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is one in a series of papers presenting a process for the removal of modified waxes from old corrugated containers by washing after alkaline hot dispersion of the recycled pulp. It presents experiments for selection of the most useful dispersants to be incorporated as wax modifiers already before the wax application. Criteria for selection were their effect on wax properties such as water and moisture resistance and their efficiency for dispersion to minimum size under hot alkaline conditions. The dispersants must also permit simple coagulation of the wax dispersion for its removal from a closed white water system. The dispersion experiments were carried out on a laboratory scale in the absence of fibers at 90°C and pH 9 to 11. Evaluated was the turbidity both at that temperature and after cooling to 20°C. For the final selection, the particle size distribution at 20°C was also measured. A few per cent of a commercial stearic acid with a minor addition of a nonionic fatty alcohol ethoxylate formula R-O-(CH2)2-O-]nH, was found to be a most suitable and economic wax additive.

  • 52. Backlund, S
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Molander, O
    Wärnheim, T
    Aggregation of tetradecyltrimethylammonium bromide in water, 1,2-ethanediol and their mixtures1989Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 131, s. 393-401Artikel i tidskrift (Refereegranskat)
  • 53. Backlund, S
    et al.
    Boström, G
    Nordli, KG
    Wärnheim, T
    YKI – Ytkemiska institutet.
    Partical phase equilibria and partition of alcohol cosurfactants in ionic microemulsions1990Ingår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 82, s. 290-295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The partial phase behaviour of quintinary microemulsions containing water (0.5 m NaCl), sodium dodecylfate, octane and alcohol, where the alcohol is a butanol or pentanol isomer, has been determined. In addition, the partition of the cosurfactant between the phases has been investigated, as well as in detail for the 1-butanol system. The efficiency of the cosurfactant for forming microemulsions is found to exhibit no simple relationship to its solubility properties. In addition, while branched alcohol cosurfactants promote the formation of solution phases at high surfactant contents.

  • 54. Backlund, S
    et al.
    Lundsten, R
    Ruths, M
    Sjöberg, M
    YKI – Ytkemiska institutet.
    Wärnheim, T
    Partial phase behavior of ionic microemulsions stabilized by sodium dodecylsulfate and alcohol cosurfactants1992Ingår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 88, s. 36-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ionic microemulsions, stabilized by sodium dodecylsulfate and alcohol cosurfactants, have been characterized with respect to phase behavior, particularly the composition of the different phases in Winsor type I, II and III systems. The system containing brine, octane, sodium dodecylsulfate and 1-butanol shows a regular phase behavior, in conformity with the anticipated behavior, i.e., 2-3-2 phases. The phase transitions with increasing 1-butanol concentration are analogous to those occurring with increasing salinity, when compared with previous investigations. For the system containing brine, cyclohexane, sodium dodecylsulfate and benzyl alcohol, the behavior becomes more complex, even at low surfactant contents. The transitions are 2-3-2-3-2 phases over a wide composition range. The compositions of the phases at equilibrium are discussed in relation to structural considerations, as determined by conductivity and NMR self-diffusion measurements.

  • 55. Bain, CD
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Langevin, D
    Meszaros, R
    Nylander, T
    Stubenrauch, C
    Complexes of surfactants with oppositely charged polymers at surfaces and in bulk2010Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 155, nr 1-2, s. 32-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Addition of surfactants to aqueous solutions of polyelectrolytes carrying an opposite charge causes the spontaneous formation of complexes in the bulk phase in certain concentration ranges. Under some conditions, compact monodispersemultichain complexes are obtained in the bulk. The size of these complexes depends on the mixing procedure and it can be varied in a controlled way from nanometers up to micrometers. The complexes exhibit microstructures analoguous to those of the precipitates formed at higher concentrations. In other cases, however, the bulk complexes are large, soft and polydisperse. In most cases, the dispersions are only kinetically stable and exhibit pronounced non-equilibrium features. Association at air-water interfaces readily occurs, even at very small concentrations. When the surfactant concentration is small, the surface complexes are usually made of a surfactantmonolayer to which the polymer binds and adsorbs in a flat-like configuration. However, under some conditions, thicker layers can be found,with bulk complexes sticking to the surface. The association at solid-water interfaces ismore complex and depends on the specific interactions between surfactants, polymers and the surface. However, the behaviour can be understood if distinctions between hydrophilic surfaces and hydrophobic surfaces are made. Note that the behaviour at air-water interfaces is closer to that of hydrophobic than that of hydrophilic solid surfaces. The relation between bulk and surface complexation will be discussed in this review. The emphasiswill be given to the results obtained by the teams of the EC-funded Marie Curie RTN “SOCON”.

  • 56. Ballo, A
    et al.
    Agheli, H
    Lausmaa, Jukka
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Thomsen, P
    Petronis, S
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Nanostructured model implants for in vivo studies: influence of well-defined nanotopoghraphy on de novo bone formation on titanium implants2011Ingår i: International Journal of Nanomedicine, ISSN 1176-9114, E-ISSN 1178-2013, Vol. 6, nr 1, s. 3415-3428Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An implantable model system was developed to investigate the effects of nanoscale surface properties on the osseointegration of titanium implants in rat tibia. Topographical nanostructures with a well-defined shape (semispherical protrusions) and variable size (60 nm, 120 nm and 220 nm) were produced by colloidal lithography on the machined implants. Furthermore, the implants were sputter-coated with titanium to ensure a uniform surface chemical composition. The histological evaluation of bone around the implants at 7 days and 28 days after implantation was performed on the ground sections using optical and scanning electron microscopy. Differences between groups were found mainly in the new bone formation process in the endosteal and marrow bone compartments after 28 days of implantation. Implant surfaces with 60 nm features demonstrated significantly higher bone-implant contact (BIC, 76%) compared with the 120 nm (45%) and control (57%) surfaces. This effect was correlated to the higher density and curvature of the 60 nm protrusions. Within the developed model system, nanoscale protrusions could be applied and systematically varied in size in the presence of microscale background roughness on complex screw-shaped implants. Moreover, the model can be adapted for the systematic variation of surface nanofeature density and chemistry, which opens up new possibilities for in vivo studies of various nanoscale surface-bone interactions.

  • 57.
    Barla, P
    et al.
    YKI – Ytkemiska institutet.
    Larsson, K
    Ljusberg-Wahren, H
    Norin, T
    Roberts, K
    YKI – Ytkemiska institutet.
    Phase equilibria in a ternary system saponin-sunflower oil monoglycerides-water : interactions between aliphatic and alicyclic amphiphiles1979Ingår i: Journal of the Science of Food and Agriculture, ISSN 0022-5142, E-ISSN 1097-0010, Vol. 30, s. 864-868Artikel i tidskrift (Refereegranskat)
  • 58. Bartholeyns, J
    et al.
    Romet-Lemonne, JL
    Chokri, M
    Buyse, M
    Velu, T
    Bruyns, C
    Malmsten, M
    YKI – Ytkemiska institutet.
    Cellular vaccines1998Ingår i: Research in Immunology, ISSN 0923-2494, E-ISSN 1879-1425, Vol. 149, s. 647-649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This project is devoted to the development of novel cellular vaccines designed to treat cancer patients. These cellular vaccines present and enhance immunogens, which will elicit a potent immune response. The goal is to achieve safe and effective immune reaction against the patient's own tumour. (1) Autologous cellular vaccines are prepared by processing circulating brood mononuclear cells outside of the patient's body (ex vivo) to differentiate them into antigen-presenting cells (APCs). Monocyte-derived APCs (MD-APCs) are then grown in the presence of exogenous target antigens (tumour cell debris, or apoptotic bodies) to become fully mature APCs. (2) Functionality for antigen presentation to T cells of ex vivo MD-APCs is evaluated in vivo. (3) Cellular vaccines are tested in selected rodent animal models. Efficiency and immune response are monitored in pertinent experimental systems for cancer. Pharmacological data are generated for clinical investigation. Tolerance and biologic effects are documented in primates. (4) The first clinical trials on cancer patients are taking place in 1998 on melanoma and prostate cancer to validate the concept. Specialized eel processors with dedicated software and standardized controls are being developed and used for the preparation of cellular vaccines. (5) The evaluation of new non-viral vectors and the validation of new non-viral transfection methods of mononuclear cells with marker genes is in progress and will lead to the ex vivo transfection of genes coding for immunostimulating cytokines or for tumour antigens in MD-APCs. Efficiency will be validated in vitro and in animal models. The ex vivo and animal model studies validate the clinical relevance of this new cellular immunotechnology. Clinical validation of individual autologous cellular vaccines in specific indications for which no treatment is presently available will allow the development of cellular and gene immunotherapy for other types of cancers.

  • 59. Bastardo, L
    et al.
    Claesson, P
    YKI – Ytkemiska institutet.
    Brown, W
    Interactions between mucin and alkyl sodium sulfates in solution. A light scattering study2002Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, s. 3848-3853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of negatively charged mucin in aqueous solutions and its interaction with anionic sodium alkyl sulfates with different hydrocarbon chain lengths were studied by means of dynamic light scattering. It was observed that mucin forms aggregates in aqueous solutions with a hydrodynamic radius above 500 nm. These aggregates dissolve when sodium dodecyl sulfate or sodium decyl sulfate is present at sufficiently high concentration, above about 0.2 cmc (critical micellar concentration). On the other hand, sodium octyl sulfate is not very effective in dissolving the mucin aggregates. The hydrodynamic radius of the dissolved mucin, decorated with some associated surfactant, is found to be in the range of 40-90 nm. The observation that the dissolving power of the sodium alkyl sulfates decreases with decreasing surfactant chain length suggests that the association between the surfactant and mucin is hydrophobically driven. The kinetics of the dissolution process depends on the surfactant concentration, a higher surfactant concentration giving rise to a more rapid dissolution of the aggregates. It was also observed that when the ionic strength is increased, the surfactant concentration needed to dissolve the mucin aggregates decreases. This can be explained by reduction of repulsive electrostatic forces by the salt.

  • 60. Bastardo, LA
    et al.
    Garamus, VM
    Bergström, M
    Claesson, PM
    YKI – Ytkemiska institutet.
    The structures of complexes between polyethylene imine and sodium dodecyl sulfate in D2O: A scattering study2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, s. 167-174Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The association between a highly branched polyelectrolyte with ionizable groups, polyethylene imine (PEI), and an anionic surfactant, sodium dodecyl sulfate (SDS), has been investigated at two pH values, using smallangle neutron and light scattering. The scattering data allow us to obtain a detailed picture of the association structures formed. Small-angle neutron scattering (SANS) measurements in solutions containing highly charged PEI at low pH and low SDS concentrations indicate the presence of disklike aggregates. The aggregates change to a more complex three-dimensional structure with increasing surfactant concentration. One pronounced feature in the scattering curves is the presence of a Bragg-like peak at high q-values observed at a surfactant concentration of 4.2 mM and above. This scattering feature is attributed to the formation of a common wellordered PEI/SDS structure, in analogue to what has been reported for other polyelectrolyte-surfactant systems. Precipitation occurred at the charge neutralization point, and X-ray diffraction measurements on the precipitate confirmed the existence of an ordered structure within the PEI/SDS aggregates, which was identified as a lamellar internal organization. Polyethylene imine has a low charge density in alkaline solutions. At pH 10.1 and under conditions where the surfactant was contrast matched, the SANS scattering curves showed only small changes with increasing surfactant concentration. This suggests that the polymer acts as a template onto which the surfactant molecules aggregate. Data from both static light scattering and SANS recorded under conditions where SDS and to a lower degree PEI contribute to the scattering were found to be consistent with a structure of stacked elliptic bilayers. These structures increased in size and became more compact as the surfactant concentration was increased up to the charge neutralization point.

  • 61. Bastardo, LA
    et al.
    Iruthayaraj, J
    Lundin, M
    Dedinaite, A
    YKI – Ytkemiska institutet.
    Vareikis, A
    Makuska, R
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, s. 21-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO45 MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 Å. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PEO45 MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

  • 62. Bastardo, LA
    et al.
    Mészáros, R
    Varga, I
    Gilányi, T
    Claesson, PM
    YKI – Ytkemiska institutet.
    Deuterium isotope effects on the interaction between hyperbranched polyethylene imine and an anionic surfactant2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, s. 16196-16202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solvent isotope effects on the interaction between the hyperbranched cationic polyelectrolyte, polyethylene imine (PEI), and the anionic surfactant sodium dodecyl sulfate (SDS) were investigated using potentiometric titration and eletrophoretic mobility measurements. In the basic pH range a significantly higher fraction of the amine groups was found to be protonated when the PEI was dissolved in D2O compared to H2O at the same pH/pD. The difference in polymer charge in the two solvents gradually decreases with decreasing pH and it completely diminishes at around pH=4. Electrophoretic mobility measurements of PEI/SDS complexes at different pH values correlated very well with these observations. At pH/pD≈9 a much higher mobility of the PEI/SDS complexes was found at low surfactant concentrations in D2O than in H2O, and the charge neutralization point shifted to a considerably larger surfactant concentration in heavy water. These results can be explained by the significantly higher charge density of the PEI in D2O compared to H2O. On the other hand, at the natural pH/pD as well as at pH=4 and pD=4 conditions the PEI molecules have roughly equal charge density which results in very similar charged characteristics (mobilities) of the PEI/SDS complexes as well as the same charge neutralization SDS concentration. It can be concluded, that extreme care must be taken in the general analysis of those experiments where weak polyelectrolyte/surfactant aggregates are investigated in heavy water and then these observations are correlated with structures of the same system in water.

  • 63. Beneventi, D
    et al.
    Pugh, RJ
    YKI – Ytkemiska institutet.
    Carré, B
    Gandini, A
    Surface rheology and foaming properties of sodium oleate and C12(EO)6 aqueous solutions2003Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 268, s. 221-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dynamic surface tension (DST) and the surface viscoelastic modulus of sodium oleate aqueous solutions at different concentrations were measured using an image analysis tensiometer based on the oscillating bubble technique. The diffusion coefficient of oleate moieties was calculated from DST measurements and the surface viscoelastic modulus using the Langmuir–Szyszkowski and the diffusion-controlled adsorption models. The viscoelastic moduli obtained from model calculations were compared with the corresponding experimental values. The diffusion coefficient of C12(EO)6 in water and the parameters of the Langmuir–Szyszkowski adsorption isotherm were taken from the literature and used to calculate the surface viscoelastic modulus of its aqueous solutions at different concentrations. The foaming properties of both C12(EO)6 and sodium oleate solutions, viz., the foam conductance and the water volume fraction in the foam, were measured using a commercial Foamscan device. Foaming experiments with C12(EO)6 and sodium oleate solutions were carried out either under static conditions; i.e., the foam conductance and the water volume fraction were measured as a function of time after the generation of a fixed volume of foam, or under dynamic conditions; i.e., the foam conductance and the water volume fraction were measured during foam formation. The variations in the foam permeability as a function of surfactant concentration were related to the viscoelastic properties of the air/water interface and to the presence of micelles in the foam films. With foams in which the water volume fraction was higher than 0.05, the foam electrical conduction could be described using a simple parallel resistor model and their conductance measurements were related to the foam water volume fraction. The results related to water drainage under static conditions were used to interpret water drainage under dynamic conditions. Preliminary conjectures on the influence of foam permeability and water volume fraction on the yield of the flotation deinking process were drawn from these results.

  • 64. Berg, J
    et al.
    Sundberg, D
    Kronberg, B
    YKI – Ytkemiska institutet.
    Microencapsulation of emulsified oil droplets by in-situ polymerization1986Ingår i: Polym Mater Sci Eng PMSE, ISSN 1000-7555 , Vol. 54, s. 367-369Artikel i tidskrift (Refereegranskat)
  • 65.
    Berg, J
    et al.
    YKI – Ytkemiska institutet.
    Säve, G
    Håkansson, P
    Sundqvist, BUR
    Johnson, RE
    Söderström, E
    Lindquist, SE
    Crater formation in Langmuir-Blodgett films induced by electronic sputtering with fast heavy ions1987Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 51, nr 17, s. 1379-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Secondary ion formation by fast heavy ion impact (electronic sputtering) on Langmuir–Blodgett films of fatty acids has been studied. The results show unambiguously that molecular ions originate from molecules in layers other than the surface layer. Furthermore, the results indicate that craters may be formed in electronic sputtering of such films. The depth of the craters depends on the stopping power of the incident ion and lower limits of the order of 100–200 Å are obtained from the ion data.

  • 66. Berg, JM
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Forces between surfaces coated with a polymerizable surfactant before and after polymerization1994Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 163, s. 289-298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The forces between layers of a cationic polymerizable surfactant, cetyl p-vinylbenzyl dimethyl ammonium chloride (CVDAC), adsorbed onto muscovite mica have been measured with a surface force technique. The forces were measured both prior to and after partial W polymerization of the adsorbed layers, and the stability of adsorbed bilayers after dilution of the adsorption solution was studied for these two cases. Due to their large headgroup, CVDAC molecules do not pack efficiently into monolayers and bilayers. This can be observed by, for instance, the lower surface potential of adsorbed bilayers and the lower pull-off force from monolayer contact, compared to what is found for simpler surfactants like CTAB. It was also found that surface aggregates build up on top of the bilayer, due to the partly hydrophobic headgroup. When the bilayer structure, including the surface aggregates, is polymerized, it is stabilized both with respect to mechanical forces and with respect to dilution of the surrounding solution

  • 67. Berg, JM
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Neuman, RD
    Interactions between mica surfaces in sodium polyacrylate solutions containing calcium ions1993Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 161, s. 182-189Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The forces acting between negatively charged muscovite mica surfaces immersed in solutions containing sodium polyacrylate (NaPAA) have been studied. No evidence for PAA adsorption in the absence of calcium ions in the solution was found. However, at a CaCl2 concentration of about 3x10-3 M a layer of PAA adsorbed on each surface. At large separations, the forces between the PAA-coated surfaces were dominated by repulsive double-layer forces. At separations below 50-80 Å, depending on the solution conditions, an attractive force in excess of the van der Waals attraction was observed. The adhesion force between the layers was 7-8 mN/m at pH 6 and increased somewhat with increasing pH to about 9 mN/m at pH 10. We argue that both the long-range attraction and the adhesion force primarily are due to COO- - Ca2+ --OOC bridges between the opposing surfaces and possibly charge correlation effects. It was found that calcium ions bind to the PAA and to the mica surface, whereby the electrostatic repulsion between the polyelectrolyte and the surface is lowered. We suggest that this is the main re ason why Calcium ions promote the adsorption of PAA onto negatively charged minerals. However, it also seems likely that calcium ions increase the attractive interactions between the surface and the PAA segments.

  • 68. Berg, JM
    et al.
    Eriksson, LGT
    YKI – Ytkemiska institutet.
    Mixed monolayers and Langmuir-Blodgett films consisting of a fatty amine and a bipolar substance1994Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, s. 1213-1224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of two types of two-component spread monolayers at the air/water interface, docosanedioic acid/eicosylamine (DDA/EA) and 1,22-docosanediol/eicosylamine (DDO/EA), were investigated at different mixing ratios. The monolayers were studied by surface pressure-area isotherms, constant surface pressure-area relaxation isotherms and deposition onto muscovite mica with subsequent contact angle measurements. The two types of monolayers were found to behave very differently, but in both cases one of the polar groups of the bipolar substance was situated at the air side of the monolayer after compression. At moderate DDA ratios, the surface pressure-area isotherms of DDA/EA displayed a plateau, low mean molecular area for the condensed phase, and the relaxation isotherms at low surface pressures had an unusually long induction time. DDO/EA showed much less complexity in its behaviour. These differences are explained by the difference in headgroup interaction strength, which are strong for DDA/EA case (acid-amine) and weak for DDO/EA (hydroxy-amine). Due to the increased polarity/low contact angle during the deposition, the DDA/EA monolayers at DDA ratios above 50 % deposited as Z-type Langmuir-Blodgett multilayers onto mica.

  • 69. Berg, JM
    et al.
    Eriksson, LGT
    Claesson, PM
    YKI – Ytkemiska institutet.
    Nordli Børve, KG
    Three-component Langmuir-Blodgett films with a controllable degree of polarity1994Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 10, s. 1225-1234Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two different series of mixed Langmuir-Blodgett (LB) films with a controllable degree of polarity, deposited on mica, have been studied by wetting and surface force techniques. Both series contain of 50% eicosylamine (EA). Films of one series consist of EA, arachidic acid and docosanedioic acid, while those of the other consist of EA, 1-eicosanol and 1,22-docosanediol. Carboxylic acid groups give lower contact angles than hydroxy groups. Concerning the stability of the LB films in aqueous solutions, repeated exposure to a three-phase line and high salt solutions were found to cause breakdown. Surface force measurements on carboxylic acid-containing films show that films with a 0% (contact angle = 113°) and 25% (contact angle ≈ 90°) content of diacid interact with a long-range (hydrophobic) attraction across water. No similar long-range attraction is observed for the 50% case (contact angle ≈ 65°). Surface force measurements also detected instabilities and imperfections of the films.

  • 70.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Emulsions1995Ingår i: Physico-Chemical Aspects of Food Processing / [ed] Beckett, S.T., Glasgow, UK: Blackie Academic and Professional , 1995, s. 49-64Kapitel i bok, del av antologi (Refereegranskat)
  • 71.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Gums as stabilisers for emulsifier covered emulsion droplets1988Ingår i: Gums and stabilisers for the food industry / [ed] Phillips, G.O., Wedlock, D.J., & Williams, P.A., Oxford, UK: IRL Press , 1988, s. 363-369Kapitel i bok, del av antologi (Refereegranskat)
  • 72.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Surface forces in emulsions1990Ingår i: Food Emulsions / [ed] Larsson, K., & Friberg, S., Marcel Dekker, 1990, 2, s. 41-96Kapitel i bok, del av antologi (Refereegranskat)
  • 73.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Surface forces in emulsions1997Ingår i: Food Emulsions: Third edition, revised and expanded / [ed] Larsson, K. & Friberg, S., Marcel Dekker, 1997, 3, s. 57-109Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Emulsions are thermodynamically unstable systems. Therefore, the technical aim of creating "stable emulsions" has to be limited to a control of the instabillity processes (e.g., coalescence, flocculation, creaming, and Ostwald ripening). For this purpose the technologist, in principle, has two tools available: the use of mechanical devices to disperce the system, and the addition of stabilizing additives (natural or artificial) to keep it dispersed. This chapter discusses how the emulsifying additives give rise to stabilizing forces; how these forces affect the kinetics of the instability processes; how they determine the phase behavior of emulsifers; and their relation to the HLB value. The interparticle interactions are determined mainly is coated by lipids and/or proteins. In this chapter we try to point out how a knowledge of interparticle forces, phase behavior, and adsorption may provide an understanding and rationalization of many of the properties of food emulsions.

  • 74.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Fontell, K
    YKI – Ytkemiska institutet.
    Phase equilibria in the system soybean lecithin/water1983Ingår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 68, s. 48-52Artikel i tidskrift (Refereegranskat)
  • 75.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Fäldt, P
    Adsorption structures in food emulsions1992Ingår i: Emulsions: A fundamental and practical approach / [ed] Sjöblom, J., Kluwer Academic Publishers, 1992, s. 51-60Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Food emulsions in particular, but also most other technical emulsions, are complex mixtures. When surface active components adsorb from a solution of several different surface active molecules, the formed adsorbed layer can roughly be classified in three different structures, i) A monolayer containing one predominant molecule, ii) The formation of one adsorbed monolayer containing a mixture of molecules, iii)Adsorption in layers. A model of an ice cream emulsion is an example in which a layered surface structure is formed. Four different methods were applied to investigate the surface: measurements of the interfacial tension, flocculation rate measurements, electrophoretic mobility measurements and TIRF (Total Internal Reflection Fluorescence). The conclusion we made from this investigation was that the adsorption from solutions with several surface active components might lead to the formation of complex layered structures.

  • 76.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Fäldt, P
    Surface structure and surface active components in food emulsions1995Ingår i: Food Macromolecules and Colloids / [ed] Dickinson, E. & Lorient, D., Royal Society of Chemistry, 1995, s. 201-214Kapitel i bok, del av antologi (Refereegranskat)
  • 77.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Hofland, A
    Alkyd emulsions1996Ingår i: Polymeric Materials Encyclopedia / [ed] Salamone, J.C., CRC Press, 1996, s. 154-160Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Introduction: The use of waterborne alkyds as binders in coatings is not new, their history going some 30 years back in time. Mostly, this has been in the form of water soluble alkyds, with high acid numbers that provide the water solubility of the resins after neutralization with amines. Such alkyds are mostly used in industrial coatings. Emulsified water insoluble alkyds have so far found most use in the field of decorative and protective coatings, although their use is still limited. A major factor limiting the use of alkyd emulsions is their low rate of oxidative drying, together with some remaining problems concerning colloidal stability of the emulsions. Several factors are believed to contribute to the reduced drying properties of alkyd emulsions as for example interaction between the drier and other paint components and solubility properties of the drier. A water borne paint is a complex system that besides the alkyd droplets in water also contains pigments, dispersants (to stabilize the pigments), surfactants (stabilizing the alkyd droplets), thickeners and several other additives, see Figure 1. The impaired film properties may at least partly be caused by the surfactant which will remain in the paint film and act as a plasticizer. For the segment decorative and protective coatings in Western Europe the market volumes are as follows (solid binder): Solventbased, low solids: 400 ktonne/annum Waterbased, polymer dispersion: 375 ktonne/annllrn Solventbased, high solids: 20 ktonne/annum Alkyd emulsion based: 15 ktonne/annum In most cases the alkyd emulsion is used as co-binder, especially in (hiding) stains and primers for exterior use. In these segments alkyds in white spirit are however still the binder of choice. In the case of alkyd resins for the decorative field, the environmentally friendly possibilities are either as high solids systems or as waterborne emulsions. With the present state of technology, it is very unlikely that alkyd emulsions can match the performance of the present solvent based siliconized alkyds and other extreme outdoor durable systems. Because of their more conventional permeability behaviour and the higher applied layer thickness, high solids seem more suitable for this purpose. Going to the lower end of the market, high solids systems can be applied in almost every segment, the only limitation being their price. For the lowest segments (primers and stains) their application will be limited.It is in these segments that acrylic dispersions have acquired a good reputation both their performance and price have been accepted. In the middle section, ranging from normal outdoor durable alkyds to the better performance stains, alkyd emulsions can be positioned. Their versatility and excellent environmental score (no volatile organic components are necessary) make them exceptionally suitable for this. In many outdoor applications alkyd emulsions will be compared with acrylate dispersions. Typical advantages of acrylate dispersions are their low particle size, quick drying, and good outdoor durability. The last two of these advantages can also be regarded as a disadvantage, since the drying often is considered to be too quick when only small amounts (under 5 %) of coalescing agent are used. The nomenclature then changes from "quick drying" to "short open times". The advantage of good outdoor durability is a.o. based on a good hydrolysis resistance, meaning that although it may take long, once a coating based on acrylic dispersion has deteriorated, the remainders cannot be removed by the usual alkaline paint stripper or heat gun (the dispersions are thermoplastic). Instead flakes of coating will come loose and remain in the environment. The main disadvantage of acrylate dispersions however, the seriousness of which is once again depending upon the application area, is that there always has to be some compromise between film formation (low MFI ) and good blocking properties (high Tg). Since in alkyd emulsions not all chemistry is "finished" when the film is applied, these emulsions can be expected to outperform the thermoplastic dispersions when it comes to properties that are related with film formation from a low Tg material, such as penetration (one of the factors controlling adhesion) and gloss, combined with good dirt pick-up resistance. Whereas the contents of a particle in a polymer dispersion is a true polymer (MW = 100.000 to 1.000.000), in an alkyd emulsion particle we find an oligomer, with a molecular weight ranging from 2000 to 8000. To make a real polymer out of it, the help of cobalt and atmospheric oxygen is required , just as is the case with a conventional alkyd. The fact that molecular buildup still has to take place also means that "derailments" of the crosslinking process will also take place. This means that a film cast from an alkyd emulsion will still exhibit the usual alkyd yellowing and slightly pungent smell. These are caused by decadienal-like structures and hexaldehyde, respectively, resulting from decomposition of the initial hydroperoxide and subsequent beta scission. Always compare an alkyd emulsion with an alkyd and not with a polvmer dispersion in this respect. The aspects where alkyd emulsions differ mostly form solvent-borne alkyd systems are: a) that they are formulated together with water, inducing a risk of hydrolysis upon storage, b) the disperse state of the alkyd, necessitating a high degree of colloidal stability and c) the peculiarities shown in the drying properties of alkyd emulsions. These aspects will be dealt with in the following paragraphs.

  • 78.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Jönsson, A
    Sjöblom, J
    Stenius, P
    YKI – Ytkemiska institutet.
    Wärnheim, T
    Phase behaviour of binary and ternary non-aqueous aerosol OT systems1987Ingår i: Progress in Colloid and Polymer Science, ISSN 0340-255X, E-ISSN 1437-8027, Vol. 74, s. 108-112Artikel i tidskrift (Refereegranskat)
  • 79.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Stenius, P
    YKI – Ytkemiska institutet.
    Phase equilibria of dioleoulphosphatidylcholine with formamide methylformamide and dimethylformamide1987Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 91, s. 5944-5948Artikel i tidskrift (Refereegranskat)
  • 80.
    Bergenståhl, B
    et al.
    YKI – Ytkemiska institutet.
    Östberg, G
    Alkyd emulsions: Instability and drying properties1995Ingår i: Emulsions and Emulsion Stability / [ed] Sjöblom, J., Marcel Dekker, 1995, s. 327-341Kapitel i bok, del av antologi (Refereegranskat)
  • 81.
    Bergenståhl, BA
    et al.
    YKI – Ytkemiska institutet.
    Alander, J
    Lipids and colloidal stability1997Ingår i: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, E-ISSN 1879-0399, Vol. 2, s. 590-595Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polar lipids have an important role as emulsifiers and stability controlling agents in the food industry. The principal effects of the emulsifiers have been found to depend on the situation in which they are applied. They may act as stabilising additives, creating repulsive interactions between droplets. They may act as emulsifying agents, or they may destabilise emulsions by reducing protein adsorption at the oil/water interface. They may also destabilise emulsions by increasing wettability of fat crystals. Furthermore, they may form micellar or liposomal aggregates in the dispersion, influencing interactions and aggregation.

  • 82. Bergeron, V
    et al.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Structural forces reflecting polyelectrolyte organization from bulk solutions and within surface complexes2002Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 96, s. 1-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interactions between two macroscopic surfaces approaching one another underlies many of the phenomena observed in Colloid and Interface science. In Russia this gave rise to the branch of colloid science now referred to as Surface Forces. Important discoveries, such as the molecular organization of solvent molecules at an interface, have been unveiled by surface force measurements. More recently, forces and structures at macromolecular length scales have been uncovered. In particular, oscillatory force profiles have been detected from aqueous solutions containing polyelectrolytes. The force¯structure relationship can reflect organization in the bulk solution or the internal structure of the adsorbed layer. Using a range of surface force techniques, combined with X-ray and neutron scattering results, we review the main features of these fascinating systems and provide an overview of how they relate to other systems such as micellar solutions, polymer¯surfactant complexes and simple solvents.

  • 83. Bergeron, V
    et al.
    Waltermo, Å
    Claesson, PM
    YKI – Ytkemiska institutet.
    Disjoining pressure measurements for foam films stabilized by a nonionic sugar-based surfactant1996Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 12, s. 1336-1342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Disjoining pressure isotherms for foam films made from a nonionic surfactant, octyl b-glucoside, are measured at different surfactant concentrations, ionic strengths and solution pH values. Below the cmc an electrostatic double-layer repulsion is present and dominates the long-range interaction. The decay length of the forces agrees with the expected Debye length and the measured long-range interactions are consistent with solutions to the non-linear Poisson-Boltzmann equation using constant charge conditions. The deduced surface charge densities increase with pH and ionic strength but decrease with increasing surfactant concentration. At, or just above, the cmc, surfactant covers the interface and suppresses the charge sufficiently to induce a transition from a common black film to a Newton black film. Ultimately, the film stability is determined by both surface forces and elasticity. Combining both, via an overall film tension, leads to a general expression for the film elasticity.

  • 84. Bergeron, Vance
    et al.
    Claesson, Per M
    YKI – Ytkemiska institutet.
    Oscillating structural forces reflecting the organization of bulk solutions and surface complexes: Chapter 302003Ingår i: Adsorption and aggregation of surfactants in solution: Fundamentals and applications / [ed] Dinesh O . Shah and K . L . Mittal, CRC Press, 2003, s. 635-654Kapitel i bok, del av antologi (Refereegranskat)
  • 85.
    Berglin, M
    et al.
    YKI – Ytkemiska institutet.
    Pinori, E
    YKI – Ytkemiska institutet.
    Sellborn, A
    Andersson, M
    YKI – Ytkemiska institutet.
    Hulander, M
    Elwing, H
    Fibrinogen Adsorption and Conformational Change on Model Polymers: Novel Aspects of Mutual Molecular Rearrangement2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 10, s. 5602-5608Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By combining quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR), the organic mass, water content, and corresponding protein film structure of fibrinogen adsorbed to acrylic polymeric substrates with varying polymer chain flexibility was investigated. Albumin and immunoglobulin G were included as reference proteins. For fibrinogen, the QCM-D model resulted in decreased adsorbed mass with increased polymer chain flexibility. This stands in contrast to the SPR model, in which the adsorbed mass increased with increased polymer chain flexibility. As the QCM-D model includes the hydrodynamically coupled water, we propose that on the nonflexible polymer significant protein conformational change with water incorporation in the protein film takes place. Fibrinogen maintained a more native conformation on the flexible polymer, probably due to polymer chain rearrangement rather than protein conformational change. In comparison with immunoglobulin G and albumin, polymer chain flexibility had only minor impact on adsorbed mass and protein structure. Understanding the adsorption and corresponding conformational change of a protein together with the mutual rearrangement of the polymer chain upon adsorption not only has implications in biomaterial science but could also increase the efficacy of molecular imprinted polymers (MIPs).

  • 86.
    Bergström, K
    et al.
    Berol Nobel, Sweden.
    Holmberg, K
    YKI – Ytkemiska institutet. Berol Nobel, Sweden.
    Microemulsions as reaction media for immobilization proteins to hydrophilized surfaces1992Ingår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 63, s. 273-280Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of microemulsion as reaction medium for immobilization of proteins to polystyrene hydrophilized with poly(ethylene glycol) or polysaccharide has been investigated. The amount of albumin, immunoglobulin G (IgG) and collagen immobilized from microemulsion was increased 10-100 times, compared with immobilization from an aqueous buffer system. The stability of anti-IgG and interleukin-2 was studied in different microemulsion systems. Anti-IgG was found to be stable in microemulsions based on sodium bis(2-ethylhexyl)sulphosuccinate (AOT) and C12EO5, whereas the non-ionic surfactant di-C9EO9 almost instantly destroyed the antigen-binding properties. Interleukin-2 completely lost its biological activity in an AOT-based microemulsion. We have also found that the choice of microemulsion influences coupling efficiency of the protein. An AOT-based system is preferred for immobilization of mycoplasma antibody, while a microemulsion based on C12EO5 is preferred for borrelia antigen.

  • 87.
    Bergström, L
    YKI – Ytkemiska institutet.
    Characterization of the surface chemistry of silicon nitride powders1994Ingår i: Ceramic Transactions: Materials Processing and Design: Grain Boundary Controlled Properties of Fine Ceramics II, American Ceramic Society, 1994, s. 77-87Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Introduction: Silicon nitride is a ceramic material with a potential for high strength at room as well as elevated temperatures, good thermal shock resistance and relatively good oxidation resistance. However, optimal properties can only be realized when the microstructure and the grain boundary composition of the sintered body is controlled. Several studies have shown that the surface properties of the starting powder, together with the choice and addition of sintering aids, play a decisive role in determining the final properties [1-3]. However, the final properties of the sintered material depend on many different parameters. These parameters include the green-body characteristics, the physical and bulk chemical powder properties and the sintering conditions together with the powder surface chemical properties. Hence, it has been difficult to define the relationship between only the surface chemical properties and materials properties more precisely. Also, it is not clear how the relevant surface properties of silicon nitride should be characterized and quantified. This paper is a part of a review on the surface chemistry of silicon nitride [4]. The focus will be on an overview of the methods that are available to characterize relevant surface properties of ceramic powders, together with a summary on the present understanding of the surface chemistry of silicon nitride.

  • 88.
    Bergström, L
    YKI – Ytkemiska institutet.
    Hamaker constants of inorganic materials1997Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 70, s. 125-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Calculations of Hamaker constants using Lifshitz theory require the availability of accurate dielectric data, especially in the ultraviolet spectral region, and the use of a convenient and appropriate mathematical representation. In this review, a multiple oscillator model– the so called Ninham-Parsegian (N-P) representation– has been used and spectral parameters for 31 different inorganic materials (including diamond) have been generated from critically evaluated optical data or collected from the literature. For most materials, a two-oscillator model (one UV and one IR term) was used but more detailed representations were included when available. The spectral parameters presented here can be combined with previous data, mainly focused on hydrocarbon and organic systems, to yield an extensive spectral data base for both solids and liquids enabling Lifshitz calculations of Hamaker constants for many materials combinations. Non-retarded Hamaker constants for symmetric material combinations across vacuum (A1v1) and water (A1w1) have been calculated for the different materials; these calculations were performed using the full Lifshitz theory. Asymmetric combinations, A1v3 and A1w3, against four commonly used materials in atomic force microscopy studies: silica, amorphous silicon nitride, sapphire, and muscovite mica, have also been covered. The use of a new dielectric representation for water resulted in significantly lower values of A1w1 compared to previous calculations. Analytical approximations to the full Lifshitz theory were evaluated and found to give surprisingly accurate results (the Tabor-Winterton approximation) for A1v1 when the IR contribution is of minor importance. An attempt to make the TW approximation more general by establishing some scaling relationship between between n0 and wUV was met with little success; only the UV spectral parameters of the covalent oxides, sulphides and nitrides may be fitted to a simple power law relation. The Lifshitz calculations in this study was compared with an alternative method where a more detailed dielectric representation in the visible-ultraviolet spectral range was obtained through Kramers-Kronig (K-K) transformation of reflectivity data over a broad frequency range. Despite the difference in dielectric information, the two methods generally yield non-retarded Hamaker constants which do not differ significantly. This is not true for all materials, e.g. water, where a more detailed representation using either a N-P representations with several oscillators or the K-K representation must be used. It was shown that the omission of the static and low frequency contribution in the latter method may result in a significant underestimation of the value for A1w1 when the dispersive contribution becomes very small.

  • 89.
    Bergström, L
    YKI – Ytkemiska institutet.
    Lättflytande som mjölk eller trögflytande som tandkräm1997Ingår i: Kemisk Tidskrift/Kemivärlden, ISSN 1650-0725, Vol. 7, s. 57-58Artikel i tidskrift (Refereegranskat)
  • 90.
    Bergström, L
    YKI – Ytkemiska institutet.
    Rheological properties of concentrated, nonaqueous silicon nitride suspensions1996Ingår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 79, s. 3033-3040Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rheological properties of nonaqueous silicon nitride powder suspensions have been investigated using steady shear and viscoelastic measurements. The polymeric dispersant, Hypermer KD-3 adsorbed strongly on the powder surfaces and colloidally stable, fluid suspensions up to a volume fraction of Φ= 0.50 could be prepared. The concentrated suspensions all displayed a shear thinning behavior which could be modelled using the high shear form of the Cross equation. The viscoelastic response at high concentrations was dominated by particle interactions, probably due to interpenetration of the adsorbed polymer layers, and a thickness of the adsorbed Hypermer KD-3 layer, ∆≈10 nm, was estimated. The volume fraction dependence of the high shear viscosity of three different silicon nitride powders were compared and the differences, analysed by using a modified Krieger-Dougherty model, were related to effective volume effects and the physical characteristics of the powders. The significantly lower maximum volume fraction, Φm= 0.47, of the SN E-10 powder was referred to the narrow particle size distribution and the possibility of an unfavourable particle morphology.

  • 91.
    Bergström, L
    YKI – Ytkemiska institutet.
    Rheology of concentrated suspensions1994Ingår i: Surface and Colloid Chemistry in Advanced Ceramics Processing / [ed] Pugh, R.J. & Bergström, L., Marcel Dekker, 1994, s. 193-244Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Various aspects of alkyd emulsion technology have been investigated. Firstly, the influence of alkyd oil length, acid value and hydroxyl number, as well as the type of surfactant used as emulsifier, on shear stability of alkyds emulsions have been studied. It was found that the acid value was the most important alkyd parameter, the stability increasing with increasing oil length. It is also shown that anionic surfactants give emulsions with small droplet sizes down at lower concentrations than nonionics. Secondly, polymerizable nonionic surfactants have been tested as emulsifiers and compared with conventional surfactants of the same HLB. It was found that surfactants capable of participating in the autoxidative curing process give faster drying and improved film hardness compared with non-reactive surfactants. Thirdly, the distribution of driers between the alkyd phase and the water phase has been investigated. It was found that low pH and the use of hydrophilic anionic surfactants, such as SDS, favour partitioning of cobalt into the aqueous phase which is unfavourable with respect to drying properties.

  • 92.
    Bergström, L
    YKI – Ytkemiska institutet.
    Shear thinning and shear thickening of concentrated ceramic suspensions1998Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 133, s. 151-155Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The steady shear properties of two important ceramic systems; Si3N4 powder and the composite system SiC whiskers and A1203 particles, has been investigated. The concentrated, colloidally stable powder suspensions displayed a shear thinning behaviour with an approach to a plateau at high shear rates. The concentrated aqueous SiCw and composite suspensions showed a strong, sometimes discontinuous, shear thickening at some critical shear rate which was attributed to a possible order-disorder transition of the suspension structure. It was possible to fit the volume fraction dependence of the colloidally stable ceramic suspensions to a modified Krieger-Dougherty model which yields values of the maximum volume fraction; Φm. Large differences in Φm could be correlated to the differences in shape between the whiskers and powders. The viscosity of the composite suspensions were sucessfully predicted from the Farris theory using the rheological data for the separate components.

  • 93.
    Bergström, L
    YKI – Ytkemiska institutet.
    Surface chemical characterization of ceramic powders1994Ingår i: Surface and Colloid Chemistry in Advanced Ceramics Processing / [ed] Pugh, R.J. & Bergström, L., Marcel Dekker, 1994, s. 71-125Kapitel i bok, del av antologi (Refereegranskat)
  • 94.
    Bergström, L
    YKI – Ytkemiska institutet.
    Surface chemistry of silicon nitride powders: adsorption from non-aqueous solutions1992Ingår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 69, s. 53-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The adsorption behaviour in cyclohexane of different silicon nitride powders have been studied. Adsorption isotherms of organic probe molecules covering a wide spectra of Lewis acidity/basicity showed large variation in adsorption behaviour between the different probes. Mathematical analysis showed that the adsorption data could be described by a Langmuir-Freundlich type of isotherm. Using a previously presented model of the silicon nitride surface, it was possible to relate the variation of isoelectric point in water between the three powders to a difference in the relative site density of silanol and amino groups on the surface. It was found that the maximum concentration (M) of benzoic acid increased linearly while M of pyridine decreased with an increase in the relative amount of amino groups on the surface.

  • 95.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Probing polymeric stabilization in nonaqueous media by direct measurements2000Ingår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 83, s. 217-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The steric repulsion induced by adsorbed layers of the commercial dispersant Hypermer KD3 has been probed by direct measurements in decalin. The forces are long range (commencing at 30-40 nm) and repulsive, and the distance dependence can be modeled with a simple scaling theory expression valid for polymer brushes. We obtain layer thicknesses on the order of L~9-15 nm for the compressed layers depending on KD3 concentration while the undisturbed layers have a thickness L~23-24 nm, independent of polymer concentration. Comparision of the measured interaction lengths of compressed and undisturbed polymer layers with previous layer thickness estimates based on rheological studies shows that the polymer layers are compressed in dense suspensions.

  • 96.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Blomberg, E
    YKI – Ytkemiska institutet.
    Guldberg-Pedersen, H
    Interparticle forces and rheological properties of ceramic suspensions1999Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 159-160, s. 119-126.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dispersants have a profound influence on the suspension properties of ceramic slurries. We will illustrate the effect of polymers and polyelectrolytes on the colloidal stability and the rheological properties in both aqueous and non-aqueous media. We have related direct measurements of polymerically induced interparticle forces to the rheological properties of different ceramic systems. Simple estimates of the effective volume fractions of non-aqueous, polymerically stabilized silicon nitride suspensions gave a reasonable correspondence between calculated and measured polymer layer thicknesses. We show that PAA stabilize zirconia by an electrosteric mechanism; also, we found an excellent agreement between the presence of bridging attraction and poor colloidal stability at low surface coverage. In addition, the van der Waals forces have been quantified by theoretical calculations and direct measurements.

  • 97.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Bostedt, E
    Surface chemistry of silicon nitride powders: electrokinetic behaviour and ESCA studies1990Ingår i: Colloids and Surfaces, ISSN 0166-6622, E-ISSN 1873-4340, Vol. 49, s. 183-197Artikel i tidskrift (Refereegranskat)
  • 98.
    Bergström, L
    et al.
    YKI – Ytkemiska institutet.
    Carlström, E
    Carlsson, R
    Novel ceramic processing methods using responsive polymers1997Ingår i: Key Engineering Materials, ISSN 1013-9826, E-ISSN 1662-9795, Vol. 132-136, s. 12-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract not available.

  • 99. Bergström, L
    et al.
    Ernstsson, M
    YKI – Ytkemiska institutet.
    The effect of wet and dry milling on the surface properties of silicon nitride powders1991Ingår i: Ceramics Today: Tomorrow's Ceramics / [ed] Vincenzini, P., Elsevier, 1991, s. 1005-1014Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The effects of dry milling in air and wet miling in isopropanol, on the surface properties of silicon nitride powders have been investigated. The ground powders have been analyzed with resoect to oxygen and carbon content, electrokinetic behviour, wetting characteristics and adsorption of acidic and basic probe molecules. The results show that dry milling in air leeds to a higher degree of surface oxidation which is correlated to substantially lower isoelectric points for dry milled vs. wet milled powders. The wet milled powders were contaminated by an adsorbed layer of isopropanol which resulted in an initially hydrophobic behaviour and low levels of adsorption of most probe molecules. This coating can be removed by heat treatment at elevated tempratures.

  • 100. Bergström, L Magnus
    et al.
    Skoglund, Sara
    Danerlöv, Katrin
    YKI – Ytkemiska institutet.
    Garamus, Vasil M
    Pedersen, Jan Skov
    The growth of micelles, and the transition to bilayers, in mixtures of a single-chain and a double-chain cationic surfactant investigated with small-angle neutron scattering2011Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 22, s. 10935-10944Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-assembly in aqueous mixtures of a single-chain (DTAB) and a double-chain cationic surfactant (DDAB) has been investigated with small-angle neutron scattering (SANS). Small oblate spheroidal micelles formed by DTAB grow with respect to width and length to form mixed ellipsoidal tablet-shaped micelles as an increasing fraction of DDAB is admixed into the micelles. The growth behaviour of the micelles is rationalized from the general micelle model in terms of three bending elasticity constants spontaneous curvature (H-0), bending rigidity (k(c)) and saddle-splay constant ((k(c)) over bar kc). It is found that micelles grow with respect to width, mainly as a result of decreasing k(c)H(0), and in the length direction as a result of decreasing k(c). The micelles are still rather small, i.e. about 140 angstrom in length, as an abrupt transition to large bilayer aggregates is observed. The micelle-to-bilayer transition is induced by changes in aggregate composition and is observed to occur at a mole fraction of DDAB equal to about x = 0.48 in D2O, which is a significantly higher value than previously observed for the same system in H2O (x = 0.41). An abrupt micelle-to-bilayer transition is in agreement with predictions from the general micelle model, according to which an abrupt transition from micelles to bilayers is expected to occur at xi H-0 = 1/4, where x is the thickness of the self-assembled interface, and we may conclude that H-0(D2O) > H-0(H2O) for the system DDAB/DTAB in absence of added salt. Samples with bilayers are found to be composed of bilayer disks coexisting with vesicles. Disks are found to always predominate over vesicles with mass fractions about 70-90% disks and 10-30% vesicles. Micelles, disks and vesicles are observed to coexist in a few samples close to the micelle-to-bilayer transition.

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