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Öğe Composition of mixed anionic/nonionic surfactant micelles(Amer Oil Chemists Soc A O C S Press, 2000) Akbas, H; Iscan, M; Sidim, TA proposed method of determining the composition of mixed micelles in equilibrium with monomer of known composition is described. The systems were sodium dodecyl sulfate-polyoxyethylene 23 lauryl ether (Brij 35) in water and in 0.1 M sodium chloride solution at 25 degrees C. This technique applies the Gibbs-Duhem equation to the mixed micelle, which is treated as a pseudophase. This proposed methodology, which needs only critical micelle concentration data as a function of monomer composition, is applied to an anionic/nonionic surfactant pair. The calculated monomer-micelle equilibrium is found to be very similar to the much-used regular solution for nonideal systems.Öğe Effect of hydrogenation on density and viscosity of sunflowerseed oil(Amer Oil Chemists Soc, 1995) Topallar, H; Bayrak, Y; Iscan, MThe densities and viscosities of unhydrogenated and hydrogenated sunflowerseed oils have been determined at temperatures ranging from 25 to 50 degrees C at 5 degrees C intervals. The densities of these oils vary linearly with temperature. The Values of the parameters for the density equation have been calculated. Smooth curves were obtained when the changes in viscosity with temperature were plotted in the form of In eta vs. 1/T. The energy of activation, the free energy of activation, and the entropy of activation have been calculated at 25 degrees C, and they decreased with the degree of unsaturation in the fatty acid chains of the sunflowerseed oil.Öğe Effect of polyoxyethylene chain length and electrolyte on the viscosity of mixed micelles(Scientific Technical Research Council Turkey, 2003) Akbas, H; Sidim, T; Iscan, MThe viscosity measurements of micelles composed of mixtures of anionic/nonionic surfactants were carried out as a function of the mole fraction of surfactants. The systems studied were sodium dodecyl sulfate (SDS)-polyoxyethylene lauryl ether (C(12)POE(n)n = 4, 10 and 23) in water and 0.1 M sodium chloride solution. In the single systems, the relative viscosity of nonionic surfactant is greater than that of SDS, and increases with the increasing level of ethylene oxide. In the mixed surfactant systems, the relative viscosities vary at the mixed molar fraction of SDS, between 0.2 and 0.3, and then the relative viscosities of mixed systems decrease with the increasing mole fraction of SDS. The experimental values show a positive deviation from ideal behavior because of mixed micelle formation and the electroviscous effect. This effect could be suppressed by the addition of an electrolyte (NaCl).Öğe A kinetic study on the autoxidation of sunflowerseed oil(Amer Oil Chemists Soc, 1997) Topallar, H; Bayrak, Y; Iscan, MUnhydrogenated and hydrogenated sunflowerseed oils were exposed to the autoxidation process by sunlight under atmospheric conditions. Experiments were carried out in equal-sized glass, PET (polyethylene terephthalate) polymer, and metal (covered by tin) containers. The reaction time was 30 d, and the reaction course was observed by determining weight changes and peroxide values (PV) of the oil samples at the same time within 2-d intervals. The logarithm of the PV was plotted against time, and straight lines were obtained from the 4th or 6th d. The autoxidation reaction constants were obtained for each oil in each container. When comparing the reaction constants, the unhydrogenated oils autoxidize easily, and the autoxidation reaction occurs faster in sunlight in glass than in the PET polymer container and much faster than in the darkness of the metal container.Öğe Kinetics of autoxidative polymerization of sunflowerseed oil(Scientific Technical Research Council Turkey, 1997) Topallar, H; Bayrak, Y; Iscan, MThe rates of polymerization of unhydrogenated and hydrogenated sunflowerseed oils were measured under atmospheric conditions in the various containers (glass, PET and metal). Polymerization rates showed a strong dependence on the degree of unsaturation and the light transmittance of the containers. The average molecular weights of polymerized oils were determined by viscosity measurements. The relationship between viscosity and average molecular weight was determined. It is seen that unhydrogenated sunflowerseed oil has a higher polymerization rate than hydrogenated oil samples in a glass container and they has higher viscosity values.Öğe Phase behavior of oil/water/nonionic surfactant systems(Taylor & Francis Inc, 2005) Bayrak, Y; Iscan, MThe phase behavior of oil/water/nonionic surfactant systems under the effect of temperature is usually only measured at an oil-to-water ratio of 1 : 1 (alpha = 0.5). It was found that with increasing oil-chain length and increasing hydrophilicity of the surfactant (Triton X-114 to Triton X-100), the three-phase region widens toward higher temperatures. The clear inclination of the fishes at constant oil-to-water ratios shows that the surfactant becomes more hydrophobic with increasing temperature. It was observed that the phase behavior of systems changes with the amount and kinds of added salts. The description of the experiments by the modified Landau-type model is satisfactory.Öğe Phase inversion temperatures of Triton X-100/1-butanol/hydrocarbon/water systems(Amer Oil Chemists Soc A O C S Press, 2004) Bayrak, Y; Iscan, MThe formation of a water-in-oil (w/o) microemulsion in Triton X-100/1-butanol/alkane/water systems was investigated at 25.0 +/- 0.1 degreesC. Phase inversion temperatures in hydrocarbon-water microemulsions stabilized with Triton X-100 were determined for different hydrocarbons. It was found that the more soluble the alkane (oil), functioning as a nonionic emulsifier, the lower was the phase inversion temperature, above which oil-in-water type microemulsions invert to w/o type. The effect of the presence of cosurfactant was studied. No phase inversion was observed in the absence of cosurfactant. The effect on phase inversion temperature of decreasing or increasing the temperature was evaluated. By definition, phase inversion was not affected by different temperatures.Öğe Studies on the phase behavior of the system non-ionic surfactant/alcohol/alkane/H2O(Elsevier, 2005) Bayrak, Y; Iscan, MMicroemulsions with 1-butanol, 1-pentanol and 1-hexanol as cosurfactants, Triton X-100, -114, -405 or mixtures of non-ionic surfactants as surfactants and, n-hexane, n-heptane, n-octane and n-decane as oils were investigated. The effects of polyoxyethylene chain length, chain length of the oil, surfactant to cosurfactant ratio, mixing of surfactants, type of cosurfactant and concentration of salt have been studied. Maximization of solubilization of oil and water was achieved for whole systems at low concentration of surfactants. Optimum surfactant/cosurfactant ratio was determined as 1/0.5. In addition, it was found that surfactant/cosurfactant ratio, type of oil and polyoxyethylene chain length of surfactant had changed the dispersion ratio. (c) 2005 Elsevier B.V. All rights reserved.Öğe Thermodynamics of dissociation and micellization of sodium, calcium, aluminum, and tin stearates in mixed organic solvents(Springer, 1997) Topallar, H; Bayrak, Y; Iscan, MSodium, calcium, aluminum, and tin stearates behave as weak electrolytes in dilute solutions (60% benzene + 40% methanol, vol/vol) below the critical micelle concentration, and conductance data can be explained on the basis of Ostwald's formula and the Debye-Huckel theory of weak electrolytes. Dissociation constants and thermodynamic parameters for dissociation and micellization of these soaps were also evaluated. Micellization was spontaneous and predominant over the dissociation process.Öğe Thermodynamics of dissociation of strontium, barium and nickel caproates in water(Scientific Technical Research Council Turkey, 1997) Topallar, H; Bayrak, Y; Iscan, MThe critical micellar concentration (CMC) and thermodynamic parameters (heat Delta H-d, free energy Delta G(d), and entropy Delta S-d, of dissociation) of aqueous solutions of strontium, barium and nickel caproates were determined by conductivity measurements. A Kraus and Bray-type expression was used to evaluate molecular conductance at infinite dilution and theromdynamic parameters. The results confirm that CMC remains unaffected by temperature in the range of 25-55 degrees C, and show that the dissociation of soaps is an exothermic reaction and nonspontaneous.
