Detergent CMC

Carboxymethyl cellulose (CMC) plays an important role in food industry. Because of high viscosity, nontoxicity, and nonallergic nature, it is used as a viscosity modifier or thickener and to stabilize emulsions in various products including ice cream. It is also a constituent of many nonfood products, such as jellies, toothpaste, laxatives, diet pills, water-based paints, detergents, textile, and various paper products. In laundry detergents, CMC is used as a soil suspension polymer which creates a negatively charged barrier to soils in the wash solution. CMC is also used as a lubricant in nonvolatile eye drops. 

In acidic media, amine oxides and anionic surfactants form precipitates the CMC is much greater than in neutral or alkaline media. Change in CMC parallels change from ionic to nonionic form. Amine oxides are stable in formulated detergent products and do not act as oxidizing agents. Composition and function of representative commercial amine oxides are given in Table 26. 

Anionic Surfactants. PVP also interacts with anionic detergents, another class of large anions (108). This interaction has generated considerable interest because addition of PVP results in the formation of micelles at lower concentration than the critical micelle concentration (CMC) of the free surfactant the mechanism is described as a "necklace" of hemimicelles along the polymer chain, the hemimicelles being surrounded to some extent with PVP (109). The effective lowering of the CMC increases the surfactant s apparent activity at interfaces. PVP will increase foaming of anionic surfactants for this reason. 

Further addition of fatty acid eventually results in the formation of micelles. Micelles formed from an amphipathic lipid in water position the hydrophobic tails in the center of the lipid aggregation with the polar head groups facing outward. Amphipathic molecules that form micelles are characterized by a unique critical micelle concentration, or CMC. Below the CMC, individual lipid molecules predominate. Nearly all the lipid added above the CMC, however, spontaneously forms micelles. Micelles are the preferred form of aggregation in water for detergents and soaps. Some typical CMC values are listed in Figure 9.3. 

If one compares several commercial LAS samples for foam stability, detergency performance, critical micelle concentration (CMC), hardness sensitivity, or... 

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. 

In another study of the physical behavior of soap-LSDA blends, Weil and Linfield [35] showed that the mechanism of action of such mixtures is based on a close association between the two components. In deionized water this association is mixed micellar. Surface tension curves confirm the presence of mixed micelles in deionized water and show a combination of optimum surface active properties, such as low CMC, high surface concentration, and low surface concentration above the CMC. Solubilization of high Krafft point soap by an LSDA and of a difficulty soluble LSDA by soap are related results of this association. Analysis of dispersions of soap-LSDA mixtures in hard water shows that the dispersed particles are mixtures of soap and LSDA in the same proportion as they were originally added. These findings are inconsistent with the view that soap reacts separately with hard water ions and that the resulting lime soap is suspended by surface adsorption of LSDA. The suspended particles are responsible for surface-active properties and detergency and do not permit deposits on washed fabric unlike those found after washing with soap alone. 

The interaction of such compounds with the bilayer can result in alteration in vesicle properties such as permeability and stability of the bilayer structure. Amphiphatic compounds such as detergents (e.g., Triton and lysophosphoiipids) can intercalate in the bilayer below their critical micelle concentration (CMC) (Kitagawa et al.,... 

The water-splitting activity of detergent-solubilized and AP-trapped PS2 reaction centers was measured using a Clark electrode. As shown in Figure 4, differences between the two types of samples were minimal, with a slight decrease of activity when the pH of the P-DM solution was shifted to pH 8 and a moderate increase following addition of A8-35, dilution below the CMC of p-DM and treatment with BioBeads. 

A model analogous to the Hill model (for enzymatic reactions), which describes a more accurate dependence of the observed rate constants on surfactant concentration, was developed by Piszkiewicz. This model is applicable especially at low surfactant concentration and the data may be treated without reference to CMC. According to this model, a substrate (S) and n number of detergent molecules (D), aggregate to form critical micelle (D S), which may react to yield the product... 

In the process of realizing product quality factors by changing product formulation, the relevant performance indices have to be determined. The determination process in turn requires experience and technical expertise. For detergent products the performance indices need to be considered include (1) optimum hydrophilic-lipophilic balance, HLB0p (2) critical micelle concentration, CMC (3) soil solubilization capacity, S (4) Krafft point,... 

Since oleic acid is relatively polar, it may become emulsified by the surfactant monomer. The removal of oleic acid comes mainly from two contributions monomer emulsification and micellar solubilization. Although the Vgjj has been decreased with increasing EO number in dodecanol ethoxylates, in higher EO numbers than 5, this factor has been compensated by the Increase of monomer with increasing EO number (CMC decreases with EO number). The levelling of detergency of dodecanol ethoxylates from EO number 5 to EO number 8 has been interpreted by these reasons. The monomer emulsification of oleic acid has been clearly shown in this paper in SDS solution. The nonionic surfactants we used here have low EO numbers and show mainly the effect of solubilization. 

Addition of the dicarboxylic acid to a water/ detergent combination prevents (B) the gelling caused by a model dirt (octanol, CgOH) below the cmc (A). A The model dirt octanol (CgOH) forms a liquid crystalline phase with water and sodium octanoiate (CgOOH at pH 10) in area 3 and 4 Partial substitution of the sodium octanoate with the diacid soap (pH 10) leads to an increase of solubilization of the octanol (B). 1 aqueous... 

Membrane Osmometry. The apparatus has been described in detail elsewhere (,5). The concentration of detergent in the solution compartment was many times the CMC (10 to 100) whereas the concentration in the solvent compartment was somewhat above (i.e., 5 to 10 times) the CMC. Under these conditions, the following limiting equation applies (3-6) ... 

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