| 1. |
- Blute, Irena, et al.
(författare)
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Industrial manufactured silica nanoparticle sols. 2 : Surface tension, particle concentration, foam generation and stability
- 2009
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 337:1-3, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Several earlier papers have revealed that several key parameters, such as hydrophobicity (contact angle), size, shape and degree of agglomeration, have an important influence on the behavior of particles at the air/water interface. However, the origin of foaming with particles is still not clear. In this article, we have tentatively related surface tension measurements and particle concentrations to the generation and stability of foam produced from industrial manufactured silica nanoparticle sols. Surprisingly, only slight reductions in surface tension were observed and the differences between the hydrophophilic and partially modified hydrophobic sols were small. However, in the case of the partially modified hydrophobic sol, the surface tension/concentration gradient was found to be pH and concentration responsive. Also, the greatest reduction in Surface tension was found to occur at low pH (in the region of the pH(pzc)) and could be related to the highest foamability (foam generation) as determined in our earlier publication [1. Blute, R.J. Pugh, J. van de Pas, I. Callaghan, Silica nanoparticle sols. 1. Surface chemical characterization and evaluation of the foam generation (foamability), J. Colloid Interface Sci. 313 (2007) 645-655]. Also, after centrifugation of the moderately hydrophobic modified concentrated sols, foaming tests carried out on the supernatant indicated that the particle concentration had a dominant influence on foamability and foam stability. Since only transient foams, with relatively short lifetimes, could be produced with these modified silica nanoparticles then (a) further surface modification or the reduction of pH to increase the Surface activity or (b) the addition of a cosurfactant Would be needed to increase the foamability and achieve foams with extended lifetimes.
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| 2. |
- Blute, Irena, et al.
(författare)
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Silica nanoparticle sols 1 : Surface chemical characterization and evaluation of the foam generation (foamability)
- 2007
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 313:2, s. 645-655
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Tidskriftsartikel (refereegranskat)abstract
- Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5-40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pH(pzc) which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6-40 nm range) and (b) increased with particle concentration (within the range of 1-15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration.
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| 3. |
- Blute, Irena, et al.
(författare)
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Silica nanoparticle sols. Part 3 : Monitoring the state of agglomeration at the air/water interface using the Langmuir-Blodgett technique
- 2009
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 336:2, s. 584-591
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Tidskriftsartikel (refereegranskat)abstract
- Langmuir-Blodgett films were prepared at the air/water interface from dispersions of hydrophilic and partially, hydrophobically modified industrially manufactured silica nanoparticles. The hydrophilic particles featured expanded, fairly easily compressible, surface pressure (pi)-area (A) isotherms with well defined collapse pressures which appeared to be caused by the formation of loosely structured agglomerates which exhibited elastic behavior at low surface pressure and inelastic behavior at high surface pressure. Lateral electrostatic interparticle interactions seemingly played an important role in this hydrophilic system. This contrasted with the hydrophobically modified particles which were more difficult to disperse in the ethanol/chloroform spreading solvent and appeared to be in the semi-agglomerated state at low surface pressures and exhibited a more difficult to compress compacted film. Both types of particulate films were shown to be sensitive to the spreading environment and changes in pH were found to increase particle agglomeration which drastically reduced the particulate area for the hydrophilic sol but less so, in the case of the moderately hydrophobically modified sol. In general, the LB technique proved to be a useful method to monitor changes in the state of aggregation of narrosized silica particles at the air/water interface. These results also appear to give some support of our ideas, presented in earlier publications [1,2] in which it was suggested that the major role of the hydrophobically modified hydrophilic particles in foaming was to produce an aggregated particulate film surrounding the air/water interface which provides a physical barrier preventing coalescence of bubbles.
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| 4. |
- Corkery, Robert W., 1967-, et al.
(författare)
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Emulsion inversion in the PIT range: Quantitative phase variations in a two-phase emulsion
- 2010
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 55:10, s. 4471-4475
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Tidskriftsartikel (refereegranskat)abstract
- The phase-inversion temperature (PIT) phenomenon is for the first time given a quantitative treatment for systems having a sufficiently small surfactant content to be limited to two phases at the PIT. The results show that the early opinion of a phase transfer of the surfactant as the major event in the transversal of the temperature range is not entirely correct; the major phenomenon is instead an expulsion of water from the low-temperature aqueous micellar solution. In addition, the results unexpectedly give an indication of the existence of three phases at temperatures beneath the PIT, in spite of the the fact that system consists of only two phases at the actual PIT.
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| 5. |
- Friberg, Stig E, et al.
(författare)
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Hydrotropy : Chapter 2
- 2006. - 2nd
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Ingår i: Liquid Detergents. - : Taylor & Francis Group. - 9780824758356 ; , s. 19-38
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Bokkapitel (refereegranskat)
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| 6. |
- Friberg, Stig E, et al.
(författare)
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Phase inversion temperature (PIT) emulsification process
- 2011
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 56:12, s. 4282-4290
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative analysis is made of the phase changes during the phase inversion temperature (PIT) emulsification process of an aqueous hexadecane emulsion stabilized by a tetra-ethylene glycol dodecyl ether surfactant. The mechanical dispersion part of the process takes place at the PIT, at which temperature the emulsion contains three phases: (1) water, with only minute fractions of surfactant and hydrocarbon; (2) an inverse micellar solution, with modest fractions of solubilized water; and (3) a bicontinuous microemulsion, with large concurrent solubilization of both water and hydrocarbon. After the mechanical action at the PIT, the emulsion is immediately cooled to temperatures beneath the PIT range, reducing the number of phases in the emulsion to two, an oil/water (O/W) microemulsion with moderate surfactant and hydrocarbon content, and an inverse micellar hydrocarbon solution with a significantly greater surfactant fraction. The emulsion is characterized by its large fraction of extremely small oil drops, significantly smaller than expected from the mechanical process. These drops are commonly assumed to emanate from the hydrocarbon fraction of the original bicontinuous microemulsion, the small size of the oil drops being a rational consequence of the colloidal dispersion prior to the phase separation. The quantitative analysis of the phase fractions versus temperature revealed this assumption to be premature. The original water phase is not the final aqueous phase in the emulsion; this phase is instead formed from the microemulsion phase by absorbing the original water phase, gradually modifying its own structure to become water-continuous with the originally large hydrocarbon fraction reduced to modest levels. In the process, a part of the original microemulsion is separated, forming the small oil drops.
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| 7. |
- Mira, Isabel C., et al.
(författare)
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Foam forming revisited Part I. Foaming behaviour of fibre-surfactant systems
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - : SPCI. - 0283-2631 .- 2000-0669. ; 29:4, s. 679-688
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Tidskriftsartikel (refereegranskat)abstract
- The foaming properties of typical chemithermo-mechanical (CTMP) and kraft pulp paper making formulations in the presence of a series of surfactants were investigated using a lab-scale foaming set up. Foamability, foam stability, and bubble size distribution of the generated foam-fibre systems were measured. The foaming behaviour of the fibre/surfactant systems was found to be dependent on the surfactant concentration. Foams fulfilling the target requirements of air content (ca. 65% v/v air) and average bubble size (25 to 75 μm in radius) were obtained with all the seven surfactants tested. Three of the surfactants were found to allow for a rapid foaming in the system, namely sodium dodecyl sulphate (SDS), a commercial mixture of alkyl and ethoxylated alkyl sulphates, (MixSAES) and a commercial mixture of short chain alkyl glucosides (C8/C10Gluc). The rapid foaming is believed to be an intrinsic property of mixtures of surfactants with the right molecular structures and in the right proportion with respect to each other. On the other hand, the minimum surfactant concentrations required to reach the target foam volumes were lowest for surfactants with an anionic character. Further, the type of pulp fibre and the presence of GCC in the surfactant/pulp formulation were found to have very little effect on the foaming performance of the suspensions.
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| 8. |
- Persson, Karin, et al.
(författare)
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Creation of well-defined particle stabilized oil-in-water nanoemulsions
- 2014
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 459, s. 48-57
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Tidskriftsartikel (refereegranskat)abstract
- The preparation of oil-in-water (o/w) nanoemulsions stabilized with silica nanoparticle sols has been investigated. The emulsification was performed using a high shear homogenizer (Microfluidizer TM processor, Microfluidics, USA). The effect of different processing conditions on the droplet size distribution and stability was investigated in emulsions prepared using different types of oils, oil concentration and particle/oil ratios. It was the ability of the particles to attach to, and stabilize the newly created interface, rather than their ability to lower the interfacial tension, what proved important for the drop size of the resulting emulsions. Changes in drop size distribution with time, attributed to Ostwald ripening effects, were observed for the more soluble oils, while stable nanoemulsions with droplet size of ~100-200. nm could be produced using a virtually water-insoluble oil such as squalene.
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