Surface active agents functionalized

Defoamers. Foam is a common problem in papermaking systems (27). It is caused by surface-active agents which are present in the pulp slurry or in the chemical additives. In addition, partially hydrophobic soHd materials can function as foam stabilizers. Foam can exist as surface foam or as a combination of surface foam and entrained air bubbles. Surface foam usually can be removed by water or steam showers and causes few problems. Entrained air bubbles, however, can slow drainage of the stock and hence reduce machine speed. Another serious effect is the formation of translucent circular spots in the finished sheet caused by permanently entrained air. 

Poly(vinyl alcohol) will function as a non-ionic surface active agent and is used in suspension polymerisation as a protective colloid. In many applications it serves as a binder and thickener is addition to an emulsifying agent. The polymer is also employed in adhesives, binders, paper sizing, paper coatings, textile sizing, ceramics, cosmetics and as a steel quenchant. 

MacConkey s medium. This was introduced in 1905 to isolate Enterobacteriaceae from water, urine, faeces, foods, etc. Essentially, it consists of a nutrient medium with bile salts, lactose and a suitable indicator. The bile salts function as a natural surface-active agent which, while not inhibiting the growth of the Enterobacteriaceae, inhibits the growth of Gram-positive bacteria which are likely to be present in the material to be examined. 

Crude oils contain various amounts of indigenous surface-active agents that stabilize water-in-oil emulsions. Therefore crude oils may stabilize such emulsions. It has been shown that the effectiveness of a dispersant is dependent on both the dispersant type and the specific crude oil [309]. However, there is no apparent correlation between the degree of emulsion-forming tendency of the crude oil, which is a function of the indigenous surfactant content, and the effectiveness of the dispersant. In general, indigenous surfactants in crude oil reduce the effectiveness of the dispersant, but to an unpredictable level. 

Modem oil spill-dispersant formulations are concentrated blends of surface-active agents (surfactants) in a solvent carrier system. Surfactants are effective for lowering the interfacial tension of the oil slick and promoting and stabilizing oil-in-water dispersions. The solvent system has two key functions (1) to reduce the viscosity of the surfactant blend to allow efficient dispersant application and (2) to promote mixing and diffusion of the surfactant blend into the oil film [601]. 

Finally, one must realize that, whatever sophisticated electrodes and potentiometers one uses, their proper functioning may be disturbed by the adsorption of adventitious substances such as proteins or surface-active agents and by precipitation or film formation on the electrode surface, unless this is prevented by supersonic vibration or another cleaning procedure. 

Cationic surfactants are surface-active agents that have one or more functional groups in their molecule that ionise in aqueous solution to produce positively charged organic ions. The most representative cationic surfactants are quaternary ammonium derivatives in which the N atom is bonded to four alkyl groups. For many years, ditallow dimethylammonium chloride (DTDMAC) has been the most widely used product of this family. Its recalcitrance to biodegradation, however, has... 

The term mixed micelle refers to those micelles composed of two or more surface active agents. The sizes of micelles in a solution obey a distribution function that is characteristic of their chemical composition and the ionic nature of the solution in which they reside. 

FIGURE 3.1 Change in surface tension of water as a function of added solutes (inorganic salts such as NaCl, surface-active agents such as butyric acid). 

SOAPS. Chemically, a soap is defined as any salt of a fatly acid containing 8 or more carbon atoms. Structurally a soap consists of a hydrophilic (water compatible) carboxylic add which is attached to a hydrophobic (water repellent) hydrocarbon. Soap molecules thus combine two types of behavior in one structure part of the molecule is attracted to water and the other part is attracted to oil. This feature underlies the function of these materials as surface active agents, or surfactants. Soaps are one class of surfactants. The other classes generally are called detergents. See also Colloid Systems and Detergents. 

For substances where the half-wave potential is a function of pH, care should be taken that the solutions are well buffered. Wherever possible, the half-wave potentials obtained in the absence of surface-active substances should be compared. If necessary, the smallest possible concentration of surface-active agent is added, and this is maintained unchanged for the whole reaction series. For curves showing maxima, the half-wave potentials can be neither measured nor compared. 

The physical properties of surface active agents differ from those of smaller or nonamphipathic molecules in one major aspect, namely, the abrupt changes in their properties above a critical concentration. This is illustrated in Fig. 1, in which a number of physical properties (surface tension, osmotic pressure, turbidity, solubilization, magnetic resonance, conductivity, and self-diffusion) are plotted as a function of concentration. All these properties (interfacial and bulk) show an abrupt change at a particular concentration, which is consistent with the fact that above this concentration, surface active ions or molecules in solution associate to form larger units. These association units are called micelles and the concentration at which this association phenomenon occurs is known as the critical micelle concentration (cmc). 

Examination of the relevant theory indicates that the adjuvant effect of surface-active agents on herbicide action is maximized when the quantity FI = yL cos 0, or the film pressure at the liquid/solid interface, has a maximum value. Measurement of surface tension of 1.0% aqueous solutions and of contact angle on a number of substrates (Teflon, paraffin) and plant-leaf surfaces (soybean, com) as a function of hydrophile-lipophile balance show at least one maximum, and these values are in good agreement with earlier experimental data on herbicidal activity. 

Although it is known that the surface tension increases with increasing HLB (all other things being equal), the dependence of contact angle on this quantity has not been studied previously. On the other hand, if one assumes that the linear relation between surface tension and contact angle found by Zisman and co-workers for both pure liquids and for solutions of surface-active agents (3) as a function of concentration holds for our herbicidal systems, it appears that the quantity, n, will exhibit at least one maximum when plotted as a function of HLB. 

Function Firming agent stabilizer and thickener surface-active agent surface-finishing agent. 

Function Binder dough conditioner emulsifier and emulsifier salt flavoring agent flavor enhancer nutrient fermentation aid surface-active agent texturizer. 

Producing compounded lecithins. Compounded lecithins are special purpose products made by the direct addition and/or blending of functional additives, emulsifiers, diluents, surface active agents, and so on. 

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