Critical wetting concentration

Schulze [51] described an extensive study on C12-C14 ether carboxylic acid sodium salt (4.5 mol EO) in terms of surface tension, critical micelle concentration (CMC), wetting, detergency, foam, hardness stability, and lime soap dispersing properties. He found good detergent effect compared to the etho-xylated C16-C18 fatty alcohol (25 mol EO) independent of CaCl2 concentration, there was excellent soil suspending power, low surface tension, and fewer Ca deposits than with alkylbenzenesulfonate. 

The basic mechanism for surfactants to enhance solubility and dissolution is the ability of surface-active molecules to aggregate and form micelles [35], While the mathematical models used to describe surfactant-enhanced dissolution may differ, they all incorporate micellar transport. The basic assumption underlying micelle-facilitated transport is that no enhanced dissolution takes place below the critical micelle concentration of the surfactant solution. This assumption is debatable, since surfactant molecules below the critical micelle concentration may improve the wetting of solids by reducing the surface energy. 

Test Methods. Surface tension (y) measurements were taken by Wil-helmy method (25+0.1°C). Critical micelle concentrations (cmc) were obtained from Y logC curves. Contact angle. Type GI, Japan. Wetting test. Canvas disk method, CIS,HG-2-380-66. Foam test, Ross-Miles lather method. Emulslbillty was determined by mixing 20 ml of 2.5%... 

Polysorbate 80 is widely used as a nonionic surfactant in liquid pharmaceutical products such as inhalation, suspension, and nasal suspension products, due to its properties of solubilization, reduction of surface and interfacial tension, and wetting. Direct analysis of Polysorbate 80 is quite time consuming. Size-exclusion chromatography (SEC) has been reported [5] in which a mobile phase contained the surfactant at concentrations above the critical micelle concentration. Polysorbate 80 appeared as a very broad peak and coeluted with other peaks, which makes quantification in Nasonex impossible. 

The irradiation of micellar solutions effects the phase behavior and the critical micelle concentration (CMC). Because radiation sterilization of biopharmaceutical products is a common routine it is important to investigate the influence of radiation on surfactants that are widely used in the pharmaceutical industry for formulations as wetting agents, emulsifiers, or solubilizers. In particular, in drug formulations... 

R. Wagner, Y. Wu, L. Richter, S. Siegel, J. Weissmuller, J. Reiners, Appl. Organometal. Chem., 1998, 12(12), 843-853. Silicon-modified carbohydrate surfactants IX dynamic wetting of a perfluorinated solid surface by solutions of a siloxane surfactant above and below the critical micelle concentration. ... 

Attenuated total reflection infrared critical micelle concentration electron spectroscopy for chemical analysis hydrophilic-lipophilic balance poly(chlorotrifluoroethylene) poly(dimethylsiloxane) poly(tetrafluoroethylene) poly(trifluoropropylmethylsiloxane) glass transition temperature critical surface tension of wetting Owens-Wendt solid surface tension surface tension of aqueous solution surface tension of liquid... 

Fig. 14.a Composition-depth cf)(z) profiles near the surface (at z=0) of a binary mixture at bulk concentration bi at lower (T—>TW ) and upper (T—>TW+) limit of the first order wetting transition point b,c Cahn constructions with trajectories -2kV< ) plotted for profiles cf)(z) with decreasing (solid lines) and increasing (dashed lines) slopes. Surface boundary condition (Eq. 26) is met at points (marked by ) where surface energy derivative (-dfs/d< ))s (idotted line) intersects trajectories -2kV< > at concentrations reached at the surface. Cahn plot b corresponding to the first order transition depicted in a Cahn construction c typical for a critical wetting trajectories -2kV< > with larger extrema correspond to temperatures T[Pg.37]

Figure 10-5. Effect of concentration on critical wetting temperature for oleophobic films on platinum. (a) n-Octadecyl compounds in cetane. (b) n-Eiscosyl and n-octadecyl acids and alcohols in cetane. (c) n-Octadecyl acid and alcohol in cetane and in dicyclohexyl. Data by Bigelow, Glass and Zisman [181.

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