Micellar growth of poly(oxyethylene) nonionic surfactants with increasing temperature: deduction from critical micellization concentration-temperature relationships

Langmuir ◽  
1990 ◽  
Vol 6 (7) ◽  
pp. 1225-1228 ◽  
Author(s):  
Nagamune Nishikido
Keyword(s):  
Nonionic Surfactants ◽  
Critical Micellization Concentration ◽  
Micellar Growth ◽  
Increasing Temperature

The Effect of Several Polymers on the Phase Behavior of Micellar Fluids

1982 ◽  
Vol 22 (06) ◽  
pp. 816-830 ◽  
Author(s):  
Gary A. Pope ◽  
Kerming Tsaur ◽  
Robert S. Schechter ◽  
Ben Wang
Keyword(s):  
Phase Behavior ◽  
Nonionic Surfactants ◽  
Polymer Concentration ◽  
Salinity Range ◽  
Lower Phase ◽  
Optimal Salinity ◽  
Rich Phase ◽  
Three Phase ◽  
Phase Systems ◽  
Increasing Temperature

Abstract We made static measurements of the phase volumes of mixtures of surfactant, polymer, alcohol, water, oil, sodium chloride, and in some cases polymer additives. We also made a limited number of viscosity, phase concentration, and interfacial tension (IFT) measurements. The purpose was to determine systematically the effect of various polymers on the phase behavior of various surfactant formulations. We made measurements with and without oil (n-octane and n-octane/benzene mixtures) across a range of salinity appropriate to the particular surfactant at temperatures between 24 and 75 degrees C. Introduction The oil-free (i.e., no added oil) solutions showed a characteristic phase separation into an aqueous surfactant-rich phase and an aqueous polymer-rich phase at some sufficiently high salinity (NaCl concentration), which we call the critical electrolyte concentration (CEC). The CEC was found to be a characteristic of a given surfactant/alcohol combination that shifts with the solubility of the surfactant qualitatively the same way as does the optimal salinity: but the CEC was found independent of the polymer type, polymer concentration (between the 100- and 1,000-ppm limits investigated), and surfactant concentration. The CEC increases with increasing temperature for the anionic surfactants and decreases with increasing temperature for the nonionic surfactants. When oil was added to the mixtures, an entirely different pattern of phase behavior was observed. As salinity increases, the particular formulations form the typical sequence of lower-phase microemulsion and excess oil, middle-phase microemulsion. excess oil, and excess brine: and upper-phase microemulsion and excess brine. The sequence with polymer was precisely the same over most of the salinity range but deviated over a limited range of salinity; the three-phase region simply shifted a small distance to the left on the salinity scale. Also, and probably more significantly, some of the aqueous phases in the critical region of the shift (which is also just above oil-free CEC salinity) were found to be gel-like in nature. These apparently occur under conditions such that the polymer concentration in the excess brine of the three-phase systems becomes very high because almost all the polymer is always in the brine phase, even when the brine phase is very small. Thus an overall 1,000 ppm of polymer easily can be concentrated to 10,000 ppm or more. One of the most remarkable aspects of the phase behavior of the surfactant/polymer systems is that the same patterns are observed for all combinations of anionic and nonionic surfactants and polymers. Also, little difference was observed in the IFT values with and without polymer. The three-phase systems still exhibited ultralow IFT values. Obviously, significant differences did occur in the brine viscosities when polymer was added. The polymer-free mixtures were themselves quite viscous, however, and the viscosity of the oil-free surfactant-rich phases (above the CEC) was significantly higher when the phases were in equilibrium with a polymer-rich aqueous phase, even though they apparently contained almost no polymer. We found that the polymer-rich phases had normal viscosities, as judged by the same polymer in the same brine at the expected concentration, assuming all the polymer was in the polymer-rich phase. The effect of polymer on the systems with oil was to increase the viscosity of the water-rich phase only, with little effect on the microemulsion phase unless it was the water-rich phase. SPEJ P. 816^

Thermodynamic Micellization of Cationic-Nonionic Surfactants in Aqueous Solution Using Conductivity and Surface Tension Measurements

2021 ◽  
Vol 19 (4) ◽  
pp. 20-26
Author(s):  
Inaam H. Ali ◽  
Sameer H. Kareem ◽  
Fouad A.A. AL-Saady
Keyword(s):  
Aqueous Solution ◽  
Surface Tension ◽  
Free Energy ◽  
Critical Micelle Concentration ◽  
Mixed Micelle ◽  
Nonionic Surfactants ◽  
Mixed Micelles ◽  
Tween 20 ◽  
Standard Thermodynamic Functions ◽  
Increasing Temperature

In the current work, we discuss the mixed micelles and thermodynamic micellization of aqueous binary mixture of polyoxyethylene - 20 sorbitan-monododecanoate (Tween 20) as nonionic surfactant and Benzyldimethylhexadecyl ammonium chloride (HDBAC) as cationic surfactant using conductivity and surface tension (γ) estimations in the temperatures range (288 -318K). Critical micelle concentration (CMC) and variables of micellization, like the standard thermodynamic functions: Gibbs free energy (Δ𝐺𝑚 ⁰ ), enthalpyΔ𝐻𝑚 ⁰ ) and entropy (Δ𝑆𝑚 ⁰ ) were calculated using the variation of conductivity and γ with molar concentration and the variation of ln XCMC with temperature. The experimental CMC values were applied to calculate the mole fractions of surfactant in the mixed micelle (𝑋1 𝑚 ), the β parameter and the coefficient of activity f1and f2, using the equations proposed by Clint and Rubingh, which indicate the β parameter, is always negative. In addition, the results of thermodynamic parameters show that ΔG⁰m are negative for both individual and mixture of HDBAC-Tween20 surfactants and the values negatively increased with increasing temperature while its negative values decreasing with decreasing initial mole fraction of HDBAC.

scholarly journals The Study of Salt Induced Viscoelastic Wormlike Micelles in Aqueous Systems of Mixed Anionic/Nonionic Surfactants

1970 ◽  
Vol 23 ◽  
pp. 65-73 ◽  
Author(s):  
Rekha Goswami Shrestha ◽  
Kenji Aramaki
Keyword(s):  
Nonionic Surfactants ◽  
Wormlike Micelles ◽  
Micellar Solutions ◽  
Aqueous Systems ◽  
Zero Shear Viscosity ◽  
One Dimensional ◽  
Rheological Measurements ◽  
Micellar Growth ◽  
Dilute Aqueous Solution ◽  
Single Stress

Formation of viscoelastic wormlike micelles in aqueous systems of mixed amino acid based anionic and nonionic surfactants in presence of salt is presented. N-dodecylglutamic acid (LAD) upon neutralization with L-Lysine in 1:2 mole ratio forms globular type of micelles above critical micelle concentration and the solution follows Newtonian fluid like behavior at 25ºC. The addition of tri(oxyethylene) nmonotetradecyl ether (C14EO3) to the semi-dilute aqueous solution of the LADLysine-2 induces one dimensional micellar growth and viscosity of solution increases. After a certain concentration of C14EO3 micelles get entangled and form a rigid network of wormlike micelles and viscosity increases by several orders of magnitude. The wormlike micellar solutions show a viscoelastic character and can be described the Maxwell mechanical model with a single stress relaxation. Rheological measurements have shown that zero shear viscosity (No) increases with the C14EO3 concentration gradually at first sharpl, and then finally decreases before phase separation.Keywords: nonionic surfactant, wormlike micelles, rheology, viscoelastic solutionsDOI: 10.3126/jncs.v23i0.2098J. Nepal Chem. Soc., Vol. 23, 2008/2009 Page: 65-73

Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

Low Reynolds number flow around and heat transfer from a heated circular cylinder

2010 ◽  
Vol 1 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
B. Bolló
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Reynolds Number Flow ◽  
Two Dimensional Flow ◽  
Number Flow ◽  
Low Reynolds ◽  
Increasing Temperature

Abstract The two-dimensional flow around a stationary heated circular cylinder at low Reynolds numbers of 50 < Re < 210 is investigated numerically using the FLUENT commercial software package. The dimensionless vortex shedding frequency (St) reduces with increasing temperature at a given Reynolds number. The effective temperature concept was used and St-Re data were successfully transformed to the St-Reeff curve. Comparisons include root-mean-square values of the lift coefficient and Nusselt number. The results agree well with available data in the literature.

Molecular, rheological and physicochemical characterisation of puka gum, an arabinogalactan-protein extracted from the Meryta sinclairii tree

2020 ◽  
Author(s):  
MSM Wee ◽  
Ian Sims ◽  
KKT Goh ◽  
L Matia-Merino
Keyword(s):  
Hydrodynamic Radius ◽  
Average Molecular Weight ◽  
Gum Arabic ◽  
Water Soluble ◽  
Arabinogalactan Protein ◽  
Type Ii ◽  
Weight Average Molecular Weight ◽  
Soluble Polysaccharide ◽  
Physicochemical Characterisation ◽  
Increasing Temperature

© 2019 Elsevier Ltd A water-soluble polysaccharide (type II arabinogalactan-protein) extracted from the gum exudate of the native New Zealand puka tree (Meryta sinclairii), was characterised for its molecular, rheological and physicochemical properties. In 0.1 M NaCl, the weight average molecular weight (Mw) of puka gum is 5.9 × 106 Da with an RMS radius of 56 nm and z-average hydrodynamic radius of 79 nm. The intrinsic viscosity of the polysaccharide is 57 ml/g with a coil overlap concentration 15% w/w. Together, the shape factor, p, of 0.70 (exponent of RMS radius vs. hydrodynamic radius), Smidsrød-Haug's stiffness parameter B of 0.031 and Mark-Houwink exponent α of 0.375 indicate that the polysaccharide adopts a spherical conformation in solution, similar to gum arabic. The pKa is 1.8. The polysaccharide exhibits a Newtonian to shear-thinning behaviour from 0.2 to 25% w/w. Viscosity of the polysaccharide (1 s−1) decreases with decreasing concentration, increasing temperature, ionic strength, and at acidic pH.

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