| 1. |
- Arnold, Celine, et al.
(författare)
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Surfactant distribution in waterborne acrylic films. 2 Surface Investigation
- 2011
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 374:1-3, s. 58-68
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents results on sodium dodecyl sulfate (SDS) enrichment at the surface of pure acrylic or acrylic/laponite composite latex films. Surface concentrations were measured by Confocal Raman Spectroscopy leading to higher values than the nominal concentration of 6 wt%. X-ray Photoelectron Spectroscopy (XPS) analyses showed uppermost surface layers saturated with SDS in most cases. High resolution Atomic Force Microscopy (AFM) revealed a variety of morphologies for these surfactant top layers, highlighting the occurrence of SDS bilayers in different configurations. In an attempt to check for a correlation between the surface concentration of the surfactant in dry films and the concentration of free surfactant in water in the initial latex, this latter concentration was determined from the level of the plateau in adsorption isotherms. Adsorption studies by conductimetry showed an unexpected increase of the amount of adsorbed SDS with pH. The proposed interpretation is that, upon acrylic acid neutralization, the chains at the surface become more hydrophilic and spread out in water, revealing more sites for SDS to adsorb on. No correlation between free surfactant and surface enrichment could be established, indicating that the enrichment process is more complex than expected.
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| 2. |
- Andersson, C, et al.
(författare)
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Barrier properties and heat sealability/failure mechanisms of dispersion coated paperboard
- 2002
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Ingår i: Packaging technology & science. - 0894-3214 .- 1099-1522. ; 15, s. 209-224
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Tidskriftsartikel (refereegranskat)abstract
- Plate-like fillers are often added to improve barrier properties and to prevent blocking of dispersion coatings on paper and board. We have studied the effects of clay addition, neutralizing agent and drying conditions on water vapour permeability, water absorption, oxygen permeability and heat sealability of carboxylated styrene/butyl acrylate dispersion coatings on a pilot scale. The barrier dispersions were applied on a pre-coated side of a three-ply board, using a pre-metering roll coater. Coated strips were sealed under specified conditions of temperature, time and pressure and the sealability was assessed by measuring the peak load necessary to break the joints. The surface composition of the barrier-coated board was analysed and the mode of failure was characterized by ESCA. The occurrence of pinholes in the barrier coatings was assessed by both staining tests and ESEM/EDX analysis of the surface topography. The resulting barrier properties were satisfactory as far as resistance to water transport in both liquid and vapour form is concerned. The oxygen permeability was similar to that of similar amorphous polymers. Heat-sealing tests showed that the mode of failure was mainly cohesive in nature, as fibre tear occurred when sealed strips were separated. Neutralization with sodium hydroxide gave poor adhesion and had a negative effect on the seal strength. Barrier measurements and ESEM/EDX analysis both showed that the pinholes present extended only through the barrier coating
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| 3. |
- Bergström, L, et al.
(författare)
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The effect of wet and dry milling on the surface properties of silicon nitride powders
- 1991
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Ingår i: Ceramics Today. - : Elsevier. ; , s. 1005-1014
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Bokkapitel (refereegranskat)abstract
- 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.
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| 4. |
- Brodin, Ida, 1982-, et al.
(författare)
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Oxidative stabilisation of kraft lignin for carbon fibre production
- 2012
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 66:2, s. 141-147
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Tidskriftsartikel (refereegranskat)abstract
- With the aim of investigating kraft lignin as a raw material for carbon fibre production, different lignins have been stabilised in air at conditions varied according to a full factorial experimental design. The lignins under examination were purified kraft lignin powders originating from birch, spruce/pine and Eucalyptus globules, as well as lignin fibres originating from birch with 5% poly(ethylene oxide) (PEO) added as a plasticiser. The influence of temperature, time and heating rate on yield and glass-transition temperature (Tg) was investigated. The highest yield was achieved after stabilisation at 280C during 2 h with a heating rate of 0.2C min-1. The Tg of all lignin powders was increased when stabilisation occurred under harsher conditions. X-ray photoelectron spectroscopy analysis (XPS) of both the outer surface and the cleaved cross-section of individual lignin/PEO fibres showed a clear gradient in the degree of chemical modification, with the major change occurring on the surface resulting in the appearance of a skin-core structure after stabilisation. The behaviour of the lignin fibres during stabilisation is similar to that of pitch-based fibres, indicating good possibilities for lignin as raw material for carbon fibre production.
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| 5. |
- Bryne, Lars-Elof, et al.
(författare)
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Ageing of modified wood : Part 2: Determination of surface composition of acetylated, furfurylated, and thermally modified wood by XPS and ToF-SIMS
- 2010
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 64:3, s. 305-313
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of this work was to study the chemical composition of surfaces and ageing effects on acetylated pine (Pinus sylvestris), heat treated spruce (Picea abies), and furfurylated radiata pine (Pinus radiata) in comparison to unmodified wood. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were the instruments of choice. Observation with a low-vacuum scanning electron microscope (LV-SEM) complemented the study. The spectroscopic information was also linked to a parallel wettability study on matched wood samples by the Wilhelmy method. The results show that XPS and ToF-SIMS are two powerful tools that in combination give complementary information, both quantitative and qualitative, and are well suited for observation of the ageing process of different wood surfaces. The hydrophobization process as a result of migration of extractives during ageing was well quantified by the XPS measurements and the results correlated well with wetting results. Several specific hydrophobic substances could be identified by ToF-SIMS measurements.
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| 6. |
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| 7. |
- Dedinaite, Andra, et al.
(författare)
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Chitosan-SDS interactions at a solid-liquid interface : Effects of surfactant concentration and ionic strength
- 2003
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 107:32, s. 8181-8188
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ionic strength on adsorption of chitosan on mica as well as the impact of addition of an anionic surfactant, SDS, on the adsorbed chitosan layers is explored. It is demonstrated by chemical surface analysis (ESCA) and surface force measurements (SFA) that an elevated salt concentration leads to larger adsorbed amounts and thicker adsorption layers of this cationic polyelectrolyte. It is also shown that in contrast to the bulk, the binding of oppositely charged surfactant to the polyelectrolyte adsorbed on a negatively charged surface is facilitated by elevated ionic strength. Thus, the association process in bulk and at solid-liquid interfaces is rather different. The main point of difference is that at the solid-liquid interface one also has to consider interactions between the polyelectrolyte and the surface as well as between the surfactant and the surface.
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| 8. |
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| 9. |
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| 10. |
- Ernstsson, Marie, et al.
(författare)
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A multianalytical approach to characterize acidic adsorption sites on a quartz powder
- 2000
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Ingår i: Colloids and Surfaces A. - 0927-7757 .- 1873-4359. ; 168, s. 215-230
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Tidskriftsartikel (refereegranskat)abstract
- In this paper three methods are described to estimate the number of adsorption sites and detect adsorption sites of differing nature on mineral surfaces. The methods are solution depletion adsorption isotherms, adsorption microcalorimetry, and desorption by solvent extraction followed by surface analysis using Electron Spectroscopy for Chemical Analysis (ESCA). The number of adsorption sites is obtained from the adsorbed amount of a test molecule on a mineral surface from the ESCA data using equations based on a substrate/overlayer model, and from the adsorption isotherms the number of sites available to accommodate a monolayer of test molecules is used. Information about whether the adsorption sites are of different or similar nature is provided by the desorption method using extraction in solvents of different polarities. More quantitative information concerning interactions between test molecules and adsorption sites, and possible interaction strength distribution due to sites of differing nature, is obtained from the adsorption enthalpies measured by microcalorimetry. The systems studied included strong basic test molecules (either a fatty diamine, octadecyl amine or pyridine) adsorbed on quartz powder from a nonpolar medium, n-octane. For the desorption study, subsequent extraction was carried out in pure n-octane, followed by ethanol. Adsorption/desorption of basic test molecules on quartz is important in applications of asphalt systems where fatty amines are often added to strengthen adhesion between bitumen and stone aggregates. The quartz powder studied here has acidic adsorption sites of differing nature on the surface. The strong interaction sites are consistent with iron oxide and/or oxohydroxide (strongest interactions with the fatty diamine where both nitrogen atoms can interact) and geminal hydroxyl groups. The weaker interaction sites are consistent with hydroxyl (silanol) groups forming hydrogen bonds with the basic test molecules.
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