Surfactant properties

In addition to surfactant properties, emulsifiers are sometimes used to enhance the fat-replacer properties of hydrocoUoid systems. Off-flavors and legal restrictions limit use in this appHcation to a level below 0.5% of the finished product (41). 

The higher aUphatic amine oxides are commercially important because of their surfactant properties and are used extensively in detergents. Amine oxides that have surface-acting properties can be further categorized as nonionic surfactants however, because under acidic conditions they become protonated and show cationic properties, they have also been called cationic surfactants. Typical commercial amine oxides include the types shown in Table 1. 

Carboxylate, sulfonate, sulfate, and phosphate ate the polar, solubilizing groups found in most anionic surfactants. In dilute solutions of soft water, these groups ate combined with a 12—15 carbon chain hydrophobe for best surfactant properties. In neutral or acidic media, or in the presence of heavy-metal salts, eg, Ca, the carboxylate group loses most of its solubilizing power. 

The principal constituents of rosin (qv) are abietic and related acids. Tall oil (qv) is a mixture of unsaturated fatty and aHcycHc acids of the abietic family. Refined tall oil may be high in rosin acids or unsaturated acids, depending on the refining process. Ethoxylates of rosin acids, eg, dehydro abietic acid, are similar to fatty acid ethoxylates in surfactant properties and manufacture, except for thek stabiHty to hydrolysis. No noticeable decomposition is observed when a rosin ester of this type is boiled for 15 min in 10% sulfuric acid or 25% sodium hydroxide (90). Steric hindrance of the carboxylate group associated with the aHcycHc moiety has been suggested as the cause of this unexpectedly great hydrolytic stabiHty. 

Dodecylguanidine salts also have surfactant properties, which probably contribute to their effectiveness. 

Heat-stable, nonvolatile surfactants faciUtate processing. Resins with surfactant properties, such as styrene maleic anhydride resins, have sometimes been employed (95). 

There have been many experimental investigations that studied the interfacial and surfactant properties of block copolymers. In addition to documenting the corn-... 

Detergency may be defined as the removal of dirt from solid surfaces by surface chemical means [29], and may be related to several surfactant properties, including wetting and rewelting ability, foam generation, and surface and interfacial tension. It has long been observed... 

Additionally, the surfactant properties of filmers reduce the potential for stagnant, heat-transfer-resisting films, which typically develop in a filmwise condensation process, by promoting the formation of condensate drops (dropwise condensation process) that reach critical mass and fall away to leave a bare metal surface (see Figure 11.2). This function, together with the well-known scouring effect on unwanted deposits keeps internal surfaces clean and thus improves heat-transfer efficiencies (often by 5-10%). 

On account of its cost effectiveness as well as its favorable ecological and excellent surfactant properties, LAS is the most important anionic surfactant. The LAB capacities of the most important producers are listed in Table 1 (data... 

The color is adversely effected mainly by impurities in the LAB. In such cases LAB is refined before sulfonation with sulfuric acid. If the neutral oil content (paraffin hydrocarbons, sulfones, and/or unsulfonated LAB) is too high, the surfactant properties of the LAB are negatively affected. In such cases, for example, the paraffins are removed prior to sulfonation by treatment with molecular sieves [152]. 

For a more detailed description or modeling of the surfactant properties of the alkanesulfonates it is necessary to use individual, well-defined compounds typical of the technical mixtures. Recently, new data were obtained from a series of individual homologous alkanesulfonates in which the positions of the functional group and the cations vary [38]. 

TABLE 14 Surfactant Properties of Dodecane 1-Sulfonates with Different Counterions in Water at 25 °C... 

TABLE 15 Surfactant Properties of Homologous Sodium Alkanesulfonates in Water at 25°C... 

Sodium dodecyl sulfate is commonly used as the standard surfactant in many chemical and physicochemical determinations. It is often taken as the surfactant of reference when comparing surfactants. This can be explained by the fact that sodium dodecyl sulfate is the surfactant that can be obtained with the highest degree of purity. It can easily be produced by chlorosulfation or sulfation of pure dodecanol and purified by crystallization to obtain crystals of purity near to 100%. In addition, sodium dodecyl sulfate has outstanding surfactant properties. 

It is difficult to find an industrial sector that does not use alcohol sulfates or alcohol ether sulfates. These surfactants are rendered so versatile in their chemical structure through varying their alkyl chain distribution, the number of moles of ethylene oxide, or the cation that it is possible to find the adequate sulfate achieving the highest mark in nearly every surfactant property. This and the relative low cost are the two main reasons for their vast industrial use. 

Alcohol and alcohol ether sulfates are commonly considered as extremely rapid in primary biodegradation. The ester linkage in the molecule of these substances, prone to chemical hydrolysis in acid media, was considered the main reason for the rapid degradation. The hydrolysis of linear primary alcohol sulfates by bacterial enzymes is very easy and has been demonstrated in vitro. Since the direct consequence of this hydrolysis is the loss of surfactant properties, the primary biodegradation, determined by the methylene blue active substance analysis (MBAS), appears to be very rapid. However, the biodegradation of alcohol sulfates cannot be explained by this theory alone as it was proven by Hammerton in 1955 that other alcohol sulfates were highly resistant [386,387]. 

Some special salts of ether carboxylic acids are also described. Chloro-hexidine salts are made by neutralization of chlorohexidine base by an ether carboxylic acid having antibacterial and surfactant properties [47]. Chitosan salts of ether carboxylic acids which are tolerant of anionics and can be used as hair conditioners are also mentioned [48]. 

Besides these normal technical products, many other different types of a-sulfo fatty acid esters have been described in the literature. For example, Weil et al. prepared a-sulfopalmitates and stearates with higher alcohols [19] and also monoesters of polyhydric alcohol [39] and of hexitols and sucrose [40] for their special properties. In addition to the sodium salt, Stirton et al. used other cations, such as Li, NH4, K, Mg, and Ca, to study the relationship between the structure and the surfactant properties [30]. 

In addition to their poor solubility in water, alkyl phosphate esters and dialkyl phosphate esters are further characterized by sensitivity to water hardness [37]. A review of the preparation, properties, and uses of surface-active anionic phosphate esters prepared by the reactions of alcohols or ethoxylates with tetra-phosphoric acid or P4O10 is given in Ref. 3. The surfactant properties of alkyl phosphates have been investigated [18,186-188]. The critical micelle concentration (CMC) of the monoalkyl ester salts is only moderate see Table 6 ... 

Monoamidotriphosphate compounds have been evaluated for their combined detergent-sequestrant action [65,66]. Good surfactant properties are also attributed to organoaminodialkylenephosphonic acids. Typical compounds of this kind are the tetra- and trialkali salts of decyl-, dodecyl-, and tetradecylaminodi (methylphosphonate). Values of surface tension and detergency are given in Refs. 118 and 216-219. Wash test results, foam behavior, wetting performance, and surface tensions of aqueous solutions of phosphate esters have been tabulated [12,17,18,33,37,50,52,56,90,220]. 

Correlation between composition and properties of phosphate ester surfactants was exemplified by octyl phosphate with an optimum of foam inhibition and surfactant properties [301]. In separation and concentration of rare earth metals by liquid surfactant membranes 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester was used as carrier [302]. 

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