Common types of anionic surfactants

The following list includes most of the frequently encountered anionic surfactant types. Only the structure of the anion is shown. The most commonly used cations are Na , NH4 and triethanolammonium. 

Alkyl sulphates Alkylether sulphates Sulphated alkanolamides (also sulphated ethoxylated derivatives) Monoglyceride sulphates Sulphated alkylphenol ethoxylates (typically R = C9H19-, n = 3 or more) 

Alkylbenzene sulphonates Alkane sulphonates Alpha-olefin sulphonates (R = mainly -CH2- and -C2H4-) 

Olefin sulphonates are complex mixtures as a result of migration of the double bond during sulphonation and hydration across the double bond, resulting in the formation of hydroxyalkane sulphonates and sultones (internal esters) and the so-called disulphonic acids (actually sulphatosul-phonic acids). These are more fully discussed in chapter 5. 

Alkylnaphthalene sulphonates (typically R = C4H9-) Petroleum sulphonates, e.g. 

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AH detergent proteases are destabilized by linear alkylbenzenesulfonate (LAS), the most common type of anionic surfactant in detergents. The higher the LAS concentration and wash temperature, the greater the inactivation of the enzyme. The presence of nonionic surfactants, however, counteracts the negative effect of LAS. Almost aH detergents contain some nonionic surfactant therefore, the stabHity of proteases in a washing context is not problematic. 

In summary, this chapter reviews water-in-C02 microemulsion formation with three different types of anionic surfactants, hybrids such as H7F7 [7,11], polysurfactants such as PFPE [26-30], and the sulfosuccinates [13,16,17]. There are common patterns in the phase and structural behavior of all these systems and striking similarities with the properties of related AOT-stabilized water-in-oil microemulsions with short-chain low-density alkane solvents. In particular, the fluorosuccinates represent well-characterized surfactants, suitable for w/c systems. 

Nowadays, it is rare for infrared techniques to be used for qualitative or quantitative analysis of environmental materials. In either case, exhaustive separation of the surfactant from other materials must first be made. It is possible for inexperienced practitioners to go far wrong when identifying materials by IR, a technique best applied to pure compounds. Most environmental extracts, even after substantial cleanup, are mixtures which give complex spectra. It requires an experienced analyst to obtain useful information from the spectrum of a mixture containing unknown materials. As a general rule, a compound cannot be said to be present unless all of its characteristic absorbance bands are exhibited by the mixture. A once-common use of IR spectroscopy was confirmation of the identity of anionic surfactants isolated by the methylene blue spectrophotometric method. By proper choice of workup procedures and bands, this approach permitted exact determination of individual types of surfactants (78). 

Many different types of foaming agents are used, but nonionic surfactants are the most common, eg, ethoxylated fatty alcohols, fatty acid alkanolamides, fatty amine oxides, nonylphenol ethoxylates, and octylphenol ethoxylates, to name a few (see Alkylphenols). Anionic surfactants can be used, but with caution, due to potential complexing with cationic polymers commonly used in mousses. 

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. 

The common gangue material quartz (silica) is naturally hydrophilic and can be easily separated in this way from hydrophobic materials such as talc, molybdenite, metal sulphides and some types of coal. Minerals which are hydrophilic can usually be made hydrophobic by adding surfactant (referred to as an activator ) to the solution which selectively adsorbs on the required grains. For example, cationic surfactants (e.g. CTAB) will adsorb onto most negatively charged surfaces whereas anionic surfactants (e.g. SDS) will not. Optimum flotation conditions are usually obtained by experiment using a model test cell called a Hallimond tube . In addition to activator compounds, frothers which are also surfactants are added to stabilize the foam produced at the top of the flotation chamber. Mixtures of non-ionic and ionic surfactant molecules make the best frothers. As examples of the remarkable efficiency of the process, only 45 g of collector and 35 g of frother are required to float 1 ton of quartz and only 30 g of collector will separate 3 tons of sulphide ore. 

Surfactants in broad use may be classified into three general types (I) anionics, in which the hydrophilic portion of the molecule carries a negative charge (2) cationics. in which the charge of this portion is positive and (3) nonionics, which do not dissociate but commonly derive their hydrophilic portion from polyhydroxy or polyelhoxy structures. Ampholytic and it itlerionic surfactants are also known and arc starting to be of commercial importance. 

Emulsions are a class of disperse systems consisting of two immiscible liquids, one constituting the droplets (the disperse phase) and the second the dispersion medium. The most common class of emulsions is those whereby the droplets constitute the oil phase and the medium is an aqueous solution (referred to as O/W emulsions) or where the droplets constitute the disperse phase, with the oil being the continuous phase (W/O emulsions). To disperse a liquid into another immiscible liquid requires a third component, referred to as the emulsifier, which in most cases is a surfactant. Several types of emulsifiers may be used to prepare the system, ranging from anionic, cationic, zwitterionic, and nonioinic surfactants to more specialized emulsifiers of the polymeric type, referred to as polymeric... 

The experiments indicated that foam films rupture at pressures lower than nmax is not due to occasional reasons. Critical pressure pcr was observed with different types of films (common foam, CBF and NBF) stabilised with various kinds of surfactants [171,303]. Similar effect has been observed by Black and Herrington [261] who studied films stabilised with three anion-active surfactants. However, details on the critical pressure of film rupture will not be discussed here, since a satisfactory theoretical explanation of this effect has not been proposed so far. There are some hypothesis on the matter. Nevertheless, this parameter has been successfully employed in clarifying the role of foam films in foam stability (see Chapter 7). No doubt, this parameter provides information about the stability of the different types of foam films and is awaiting its qualitative interpretation. 

CIJ inks need to work on numerous substrates and there is a relationship between drop spread on a substrate and print quality. The amount of drop spread depends upon a number of issues in a CIJ ink, including surface tension, viscosity, solvent evaporation rate, interaction with substrate, amount and type of polymer in the ink etc. You may wish to improve the print quahty of a certain ink-substrate combination by optimally adjusting the drop spread. A common method to do this is by adding a surfactant to the ink formulation. Depending upon the chemistry of the surfactant, it will either increase or decrease drop spread, and hence is a good mechanism for tuning print quality. There are many hundreds of surfactants available, and you can use all chemical types, including anionic, cationic, non-anionic forms. Specific examples include polyoxyethylene fatty ethers and diethylhexyl sodium sulphosuccinate. 

The shape, size, and structure of these dispersed droplets depend upon a multitude of variables including the surfactant type, ionic strength, the presence of cosurfactant(s), and the amount of Avater. Commonly used surfactants are of the five general categories anionic, cationic, nonionic, amphoteric and zwitterionic. The nature of amphoteric surfactants, i.e., whether or not they behave as anionic or cationic species, is dependent on the pH or ionic strength of the aqueous phase. 

The secondary solvents used for this purpose are a surface-active agent or emulsifiers. Triton X-100 and Triton N-101 are nonionic surfactants commonly used in laboratory-prepared scintillation cocktails. Anionic surfactants give better sampleholding capacities than the nonionic surfactants for certain types of salt solutions. 

A wide range of products, including every class and type of surfactant, has been found to exhibit demulsification properties. The most commonly used products in lubricant formulations contain anionic surfactants such as alkyl-naphthalene sulphonates. Nonionic alkoxylated alkyl-phenol resins and block copolymers of ethylene oxide and propylene oxide are also used. 

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