Author: Publisher: ISBN: Category : Languages : en Pages : 112
Book Description
This work presents the importance of surface characteristics and its modification by surfactants during any process involving two phases. The change in the wetting characteristics of water by addition of surfactants has been investigated by experimental measurements of static, advancing and receding contact angles of aqueous surfactant solutions. These measurements have been carried out for a wide range of concentrations, from zero (pure water) to twice Critical Micellar Concentration (CMC) for anionic (SDS and SLES), cationic (CTAB, Ethoquad O/12, Ethoquad 18/25) and non-ionic (Triton X-100 and Triton X-305) surfactant solutions. Other means of characterizing the wettability change like spreading coefficient and adhesion tension have also been investigated. For ionic surfactants, the effect of charge on the polar head of the surfactant molecule has been investigated with the help of another important interfacial parameter called the zeta-potential or the electro-kinetic potential. The correlation between zeta-potential and wettability, both resulting from the adsorption of surfactant species onto the surface of the substrate is presented. The surfactant adsorption characteristics have been investigated under equilibrium conditions. Experimental equilibrium surface tension measurements have been carried out using Maximum Bubble Pressure Method. The differences in adsorption characteristics of ionic and non-ionic surfactants have been discussed. To facilitate comparison of different surfactants having different physical and chemical properties on common grounds, the experimental equilibrium surface tension data have been fitted with theoretically derived adsorption isotherms. The resulting curve fit parameters called the equilibrium adsorption parameters given by the Langmuir (and a) and Frumkin (, a and K) adsorption isotherms provide a quantitative means of comparing surfactant adsorption activity. Lastly, the time dependent nature of surfactant adsorption has been investigated. Experimental dynamic surface tension measurements were carried out and the dynamic adsorption parameters (D and d) have been calculated to examine the time dependent surface tension relaxation resulting from diffusion controlled surfactant adsorption. The short and long time approximations of the Ward and Tordai equation were fit to the experimental data. The surface tension relaxation time scales obtained were used to compare the activity of the surfactants.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
In this work the role played by dynamic surface tension in nucleate pool boiling of aqueous surfactant solution is experimentally investigated by simulating single bubble dynamics under both adiabatic and nucleate pool boiling conditions. High-resolution photographic records are obtained that characterize the ebullience (bubble shape, size, and post-departure translation), the mean bubble diameter at different time periods of its growth and departure, and bubble surface age (or the time interval between the newly formed interface to the attainment of departure diameter). Under adiabatic conditions, pre- and post-departure dynamics of air bubbles is visualized in water, N, N dimethyl-formamide (DMF), and ethyl alcohol (all pure liquids), and aqueous surfactant solutions of Sodium Dodecyl Sulfate (SDS), Cetyltrimethyl Ammonium Bromide (CTAB) and Octylphenoxy Plyethoxy Ethanol (Triton X-305). The respective evolution of bubble shapes, sizes, and departure frequencies is presented and the effect of the surface-active or interfacial forces is analyzed. In the case of aqueous surfactant solutions a time-dependent adsorption and desorption of the reagent molecules further exhibit the dynamic surface tension phenomena. The time-dependent molecular diffusion is found to be a function of the surfactant molecular weight, its ionic nature, number of ethylene oxide groups in its chemical structure, and its concentration in bulk solution. The dynamic surface tension is measured by the Maximum Bubble Pressure Method (MBPM), and its variations with concentrations and surface age are presented. The latter illustrates the time scales for molecular diffusion of different surfactants in water and the associated interfacial tension relaxation. In the nucleate pool boiling experiments, single bubbles are nucleated in an artificial micro cavity machined on a silicon wafer that is electrically heated. The bubble dynamics characterized by its departure diameter and bubble surface age is presented in a wide range of concentrations for the following surfactants: SDS and SLES (anionics), CTAB, Ethoquad O12/PG and Ethoquad18/25 (cationics), and Triton X-100 and Triton X-305 (non-ionics). The dynamic interfacial effects of the reagent molecules on the rapidly growing and departing liquid-vapor interface are once again found to be a function of the surfactant molecular weight, ionic nature, and number of ethylene oxide (EO) group attached to its polar head. Reagents with higher molecular weight are seen to produce bigger departure-diameter bubbles with longer bubble surface age as compared to their lighter counterparts. Also much smaller departure diameters are obtained with increasing concentration.
Author: D. Möbius Publisher: Elsevier ISBN: 0080542131 Category : Science Languages : en Pages : 679
Book Description
This publication provides comprehensive material on the chemical and physical attributes of surfactants and new models for the understanding of structure-property relationships. Surfactants Chemistry, Interfacial Properties, Applications provides efficient instruments for the prognostication of principal physicochemical properties and the technologic applicability from the structure of a surfactant through the discussion of interrelations between the chemical structure, physicochemical properties and the efficiency of technologic application. Also included are informative overviews on new experimental techniques and abundant reference material on manufacturers, nomenclature, product properties, and experimental examples. The publication is accompanied by a CD-ROM, which is needed for the application of the thermodynamic and kinetic models to experimental data.
Author: Milton J. Rosen Publisher: John Wiley & Sons ISBN: 0470541946 Category : Technology & Engineering Languages : en Pages : 624
Book Description
Now in its fourth edition, Surfactants and Interfacial Phenomena explains why and how surfactants operate in interfacial processes (such as foaming, wetting, emulsion formation and detergency), and shows the correlations between a surfactant's chemical structure and its action. Updated and revised to include more modern information, along with additional three chapters on Surfactants in Biology and Biotechnology, Nanotechnology and Surfactants, and Molecular Modeling with Surfactant Systems, this is the premier text on the properties and applications of surfactants. This book provides an easy-to-read, user-friendly resource for industrial chemists and a text for classroom use, and is an unparalleled tool for understanding and applying the latest information on surfactants. Problems are included at the end of each chapter to enhance the reader’s understanding, along with many tables of data that are not compiled elsewhere. Only the minimum mathematics is used in the explanation of topics to make it easy-to-understand and very user friendly.
Author: Michael Patrick Mulqueen Publisher: ISBN: Category : Languages : en Pages : 339
Book Description
(Cont.) (i) repulsive, steric interactions, which were modeled using a hard-disk treatment, and (ii) attractive, van der Waals interactions, which were modeled using a virial expansion, truncated to second order in surfactant surface concentration. Since both the hard-disk size and the second-order virial coefficients characterizing these interactions can be deduced from the known molecular structures of the surfactants, this surface equation of state contains no experimentally determined parameters. This nonionic surface equation of state was subsequently modified to incorporate electrostatic effects associated with charged surfactants. For mixtures that contain only a single ionic surfactant species, the electrostatic contribution to the surface equation of state was computed using a Gouy-Chapman based approach, which also included a Stern layer of counterion exclusion. This electrostatic description assumes that all of the electrostatic charge on the adsorbed surfactant molecules is located on a single two-dimensional charge layer. The Gouy-Chapman model was then extended to mixtures that contain multiple ionic surfactants, or surfactants that contain multiple charged groups (such as zwitterionic surfactants) by treating the case of multiple, two-dimensional charge layers at the interface. This extended theoretical framework is capable of treating any number of surfactant components containing any number of charged groups ...
Author: Victor M. Starov Publisher: CRC Press ISBN: 1420016172 Category : Science Languages : en Pages : 542
Book Description
Wetting and Spreading Dynamics explains wetting phenomena when a liquid partially or completely wets solid or immiscible liquid surfaces. Written for both newcomers and experienced researchers in the field, the book uses principles and terminology from colloid science, fluid mechanics, and thermodynamics to solve equilibrium and dynamic prob
Author: Clarence A. Miller Publisher: CRC Press ISBN: 1420044435 Category : Science Languages : en Pages : 524
Book Description
Since the publication of the first edition of Interfacial Phenomena, the interest in interfaces and surfactants has multiplied, along with their applications. Experimental and theoretical advances have provided scientists with greater insight into the structure, properties, and behavior of surfactant and colloid systems. Emphasizing equil
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Author: Peter Kroll
Author: D. Möbius
Author: Delaina Annette Amos
Author: Milton J. Rosen
Author: Jason Shin
Author: Michael Patrick Mulqueen
Author: Victor M. Starov
Author: Clarence A. Miller