Types of Surfactants

Conventional surfactants are classified as anionic, cationic, non-ionic or amphoteric, according to the charge carried by the surface-active part of the molecule  

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Dispersion Resins. Polytetrafluoroethylene dispersions in aqueous medium contain 30—60 wt % polymer particles and some surfactant. The type of surfactant and the particle characteristics depend on the appHcation. These dispersions are appHed to various substrates by spraying, flow coating, dipping, coagulating, or electro depositing. 

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

In hair coloring a light ash blond shade may require as Httie as 0.5—1% of intermediates, whereas a tme black may require up to about 5%. In principle, the formulator blends precursors that yield red, blue, and yellow dyes. The base in which the components are dissolved or suspended is similar to that used in simple bleaches and may include alkanolamides, various types of surfactants, thickening agents, and solvents. Removal of undesirable dyes is achieved by treating the discolored hair with a powerful reductant of the sulfite family. 

Internal surfactants, i.e., surfactants that are incorporated into the backbone of the polymer, are commonly used in PUD s. These surfactants can be augmented by external surfactants, especially anionic and nonionic surfactants, which are commonly used in emulsion polymerization. Great attention should be paid to the amount and type of surfactant used to stabilize urethane dispersions. Internal or external surfactants for one-component PUD s are usually added at the minimum levels needed to get good stability of the dispersion. Additional amounts beyond this minimum can cause problems with the end use of the PUD adhesive. At best, additional surfactant can cause moisture sensitivity problems with the PUD adhesive, due to the hydrophilic nature of the surfactant. Problems can be caused by excess (or the wrong type of) surfactants in the interphase region of the adhesive, affecting the ability to bond. 

From the data in Table 5 it can be seen that the CMC depends on the type of surfactant and, within a series of similar or homologous compounds, on the chain length, i.e., molecular weight of the compound. For the three AOS compounds it is seen that the CMC of the lowest molecular weight product is about twice the value of the other two products. The CMC values of the commer-... 

Also the a-ester sulfonates are less important today. In the Federal Republic of Germany, for example, the total production of surfactants was about 700,000 t/a in 1993. For a more detailed analysis of different types of surfactants, use must be made of data collected before the unification of Germany. In 1988 the consumption of surfactants in detergents was about 227,500 t/a, the consumption of anionic surfactants was about 116,000 t/a and less than 1000 t/a of a-sulfo fatty acid esters [5] (the values refer to German Detergent Law). 

There are many parallels between phosphates and sulfates of aliphatic alcohols. Both types of surfactants contain ester bonds undergoing hydrolysis in acid solutions. In that case the starting materials are received once more. By dry heating of the salts above a temperature of 140°C destruction will occur forming the corresponding alkenes and an inorganic acid salt. In the same way as sulfonic and sulfinic acids are formed by C-S bonds, C-P bonds lead to phosphonic and phosphinic acids. 

Phosphorus-containing surfactants often possess particular properties by themselves or in combination with other types of surfactants. They are therefore proposed for fields of application which can only be covered by other surfactants with difficulty. Their wide variety enables them to become tailored for different requirements. Further possibilities can be developed in conjunction with other surfactants. Their solubility in saline solution extends their field of application beyond the limits for common surfactants. 

The reaction of step 2 is carried out by heating the reagents with various acid catalysts, such as orthophosphoric acid or its acid salts, bringing the pH down to 2.3-3.2 [4]. The Igepon A type of surfactant is quite susceptible to hydrolysis, particularly on the alkaline side, as is characteristic for most esters of carboxylic acids. It is therefore used most advantageously at a fairly neutral pH, such as combination soap-syndet toilet bars. 

Although only the types of surfactants presently used in main detergent formulation have been indicated, the system allows for processing of a wider range of product while still complying with the maintenance of the quality level of the feed. Moreover, products like hydrotropes or blends of surfactants and inorganic salts can be conveniently processed to yield preformulated surfactant bases ready for incorporation in formulated detergents. 

For example, for alkyl (8-16) glycoside (Plantacare 818 UP) non-ionic surfactant solution of molecular weight 390 g/mol, an increase in surfactant concentration up to 300 ppm (CMC concentration) leads to a significant decrease in surface tension. In the range 300 < C < 1,200 ppm the surface tension was almost independent of concentration. In all cases an increase in liquid temperature leads to a decrease in surface tension. This surface tension relaxation is a diffusion rate-dependent process, which typically depends on the type of surfactant, its diffusion/absorption kinetics, micellar dynamics, and bulk concentration levels. As the CMC is approached the absorption becomes independent of the bulk concentration, and the surfactant... 

Effect of the types of surfactants on the morphology of silicalite samples... 

The application of microemulsions in foods is limited by the types of surfactants used to facilitate microemulsion formation. Many surfactants are not permitted in foods or only at low levels. The solubilization of long-chain triglycerides (LCTs) such as edible oils is more difficult to achieve than the solubilization of short- or medium-chain triglycerides, a reason why few publications on microemulsions are available, especially because food-grade additives are not allowed to contain short-chain alcohols (C3-C5). 

Studies of flow-induced coalescence are possible with the methods described here. Effects of flow conditions and emulsion properties, such as shear rate, initial droplet size, viscosity and type of surfactant can be investigated in detail. Recently developed, fast (3-10 s) [82, 83] PFG NMR methods of measuring droplet size distributions have provided nearly real-time droplet distribution curves during evolving flows such as emulsification [83], Studies of other destabilization mechanisms in emulsions such as creaming and flocculation can also be performed. 

Hall, B.E. "Workover Fluids. Part I - Surfactants have differing chemical properties that should be understood to ensure proper application," World Oil(May 1986) 111-114 ibid "Part 2 - How the various types of surfactants are used to improve well productivity," World Oil(June 1986) 64-67 ibid "Part 3 - Use of alcohols and mutual solvents in oil and gas wells," World Oil(July 1986) 65-67 ibid "Part 4 - Use of Clays and fines stabilizers and treaters," World Oil(October 1986) 61-63 ibid "Part 5 - How certain chemicals react to stabilize clays and fines in the formation," World Oil(December 1986), 49,50. 

The choice should be optimized as a function of the type of surfactants to be desorbed and the temperature and characterictics of reservoirs. 

The therapy for IRDS includes mechanical ventilation with continuous positive airway pressure. This maintains adequate ventilation and prevents airway collapse between breaths with the formation of atelectasis. Therapy also includes administration of exogenous pulmonary surfactant. Two types of surfactants are used to prevent and treat IRDS in the U.S. These include surfactants prepared from animal sources as well as synthetic surfactants. Exogenous pulmonary surfactants are administered as a suspension (in saline) through the endotracheal tube used for mechanical ventilation. 

A surfactant was defined in Chapter 8 as an agent, soluble or dispersible in a liquid, which reduces the surface tension of the liquid [1]. It is helpful to visualise surfactant molecules as being composed of opposing solubility tendencies. Thus, those effective in aqueous media typically contain an oil-soluble hydrocarbon-based chain (the hydrophobe) and a smaller water-solubilising moiety which may or may not confer ionic character (the hydrophile). The limitations of space do not permit a comprehensive detailed treatment of the chemistry of surfactants. The emphasis is therefore on a broad-brush discussion of the principal types of surfactant encountered in textile preparation and coloration processes. Comprehensive accounts of the chemistry and properties of surfactants are available [2-13]. A useful and lucid account of the chemistry and technology of surfactant manufacturing processes is given by Davidsohn and Milwidsky [ 14] ... 

Any hydrophobe can yield each of the main (i.e. anionic, cationic, nonionic or amphoteric) types of surfactant in much the same way as the same chromogenic system can be used in anionic, basic or disperse dyes. This will be demonstrated in the following sections, dealing with each class of surfactant, using the cetyl-containing (C16H33) hydrophobe. 

Carboxylates (9.4, where R is the long-chain hydrophobe and X the cation) represent the oldest type of surfactants, since they could be obtained from naturally occurring fats and oils long before the advent of the petrochemical industry sodium heptadecanoate (9.5), for example, incorporates the cetyl group as hydrophobe. Sodium stearate, sodium palmitate and sodium oleate are the simplest carboxylates generally used as surfactants. Alkylaryl compounds (9.6) are also known. 

The physicochemical data underline the striking influence of the dicyclopentadienyl unit on the properties of these silicone surfactants. In comparison to conventional products [7], the critical micelle formation concentration was lowered for up to two orders of magnitude whereas the minimum surface tension reached rose only slightly. The data collected indicate that the type of surfactant has been changed from the initial "effective" to a more "efficient" one. 

As mentioned previously, deca-BDE was considered for a long time as a practically non-toxic compound, due to its low availability. However, the results of both experiments have clearly demonstrated that this pollutant is bioavailable in aqueous phase in the presence of Tween 80. Considering that wastewater discharged into the environment often contains different types of surfactants,... 

Gauffre, F. and Roux, D. (1999) Studying a new type of surfactant aggregate ( Spherulites ) as chemical microreactors. A first example Copper ion entrapping and particle synthesis. Langmuir, 15, 3738-3747. 

Table 1 shows examples of these four types of surfactants and their corresponding structures. 

In recent years different types of surfactants have been used, in concentrations above their cmc, forming normal micelles, to improve different aspects of chemiluminescent reactions. Though the choice of the best surfactant depends on the characteristics of the chemiluminescent reaction, the surfactants most used have been the cationic (fundamentally quaternary ammonium salts) and to a lesser degree the anionic, the nonionic, and the zwiterionic compounds. 

Fig. 4.6 Correlation of relative dynamic surface pressures with foam kinetics data dh/dt as a function of the type of surfactant, alkyl chain length and salt concentration [47],...

Toshima et al. obtained colloidal dispersions of platinum by hydrogen- and photo-reduction of chloroplatinic acid in an aqueous solution in the presence of various types of surfactants such as dodecyltrimethylammonium (DTAC) and sodium dodecylsulfate (SDS) [60]. The nanoparticles produced by hydrogen reduction are bigger and more widely distributed in size than those resulting from the photo-irradiation method. Hydrogenation of vinylacetate was chosen as a catalytic reaction to test the activity of these surfactant-stabilized colloids. The reaction was performed in water under atmospheric pressure of hydrogen at 30 °C. The photo-reduced colloidal platinum catalysts proved to be best in terms of activity, a fact explained by their higher surface area as a consequence of their smaller size. 

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