Surfactant performance

The alpha-olefin sulfonates (AOS) have been found to possess good salt tolerance and chemical stabiUty at elevated temperatures. AOS surfactants exhibit good oil solubilization and low iaterfacial tension over a wide range of temperatures (219,231), whereas less salt tolerant alkylaromatic sulfonates exhibit excellent chemical stabiUty. The nature of the alkyl group, the aryl group, and the aromatic ring isomer distribution can be adjusted to improve surfactant performance under a given set of reservoir conditions (232,233). 

Cationic, anionic, and amphoteric surfactants derive thek water solubiUty from thek ionic charge, whereas the nonionic hydrophile derives its water solubihty from highly polar terminal hydroxyl groups. Cationic surfactants perform well in polar substrates like styrenics and polyurethane. Examples of cationic surfactants ate quaternary ammonium chlorides, quaternary ammonium methosulfates, and quaternary ammonium nitrates (see QuARTERNARY AMMONIUM compounds). Anionic surfactants work well in PVC and styrenics. Examples of anionic surfactants ate fatty phosphate esters and alkyl sulfonates. 

Nonionic surfactants perform well in nonpolar polymers such as polyethylene and polypropylene. Examples of nonionic surfactants ate ethoxylated fatty amines, fatty diethanolamides, and mono- and diglycetides (see Amines, fatty amines Alkanolamines). Amphoteric surfactants find Httle use in plastics (134). 

The prediction that LC-MS will become a powerful tool in the detection, identification and quantification of polar compounds such as surfactants in environmental analysis as well as in industrial blends and household formulations has proven to be true. This technique is increasingly applied in substance-specific determination of surfactants performed as routine methods. From this it becomes obvious that no other analytical approach at that time was able to provide as much information about surfactants in blends and environmental samples as that obtainable with MS and MS-MS coupled with liquid insertion interfaces. 

Composition vs. performance. There are a number of key trends that apply to alkyl sulphates, related to the influence of the hydrophobe on surfactant performance, and understanding these can help a formulator select the optimum surfactant for a product. 

Foam exhibits higher apparent viscosity and lower mobility within permeable media than do its separate constituents.(1-3) This lower mobility can be attained by the presence of less than 0.1% surfactant in the aqueous fluid being injected.(4) The foaming properties of surfactants and other properties relevant to surfactant performance in enhanced oil recovery (EOR) processes are dependent upon surfactant chemical structure. Alcohol ethoxylates and alcohol ethoxylate derivatives were chosen to study techniques of relating surfactant performance parameters to chemical structure. These classes of surfactants have been evaluated as mobility control agents in laboratory studies (see references 5 and 6 and references therein). One member of this class of surfactants has been used in three field trials.(7-9) These particular surfactants have well defined structures and chemical structure variables can be assigned numerical values. Commercial products can be manufactured in relatively high purity. 

However, there are potential objections to the use of a one atmosphere foaming experiment. These must be considered to determine the relevance of these experiments to surfactant performance in a formation. Bikerman has stated that in one atmosphere experiments the height and volume of the foam obtained depend on the details of the shaking procedure...and thus cannot be used to characterize the foaminess of a liquid in a (reasonably) absolute manner...the foam heights reproduced are specific for the test procedure selected and have no general validity. (10)... 

The limitation of the use of one atmosphere foaming experiments to rank order the predicted surfactant performance in permeable media rather than in quantitatively or semi-quantitatively predicting the actual performance of the surfactants under realistic use conditions has already been mentioned. Multiple correlation analysis has its greatest value to predicting the rank order of surfactant performance or the relative value of a physical property parameter. Correlation coefficients less than 0.99 generally do not allow the quantitative prediction of the value of a performance parameter for a surfactant yet to be evaluated or even synthesized. Despite these limitations, multiple correlation analysis can be valuable, increasing the understanding of the effect of chemical structure variables on surfactant physical property and performance parameters. 

Predictions of surfactant performance made based on multiple correlation analysis may not be valid if the surfactants involved have chemical structure parameters outside the range used to define the correlation equation. 

STEROX NJ surfactant is one of the most versatile nonionic surfactants known. It is used in almost every type of industrial surfactant application because it is a powerful detergent, emulsifier and processing aid. This surfactant performs best at temperatures below 51C (124F). 

STEROX NK surfactant is similar to STEROX NJ but is used where a higher temperature or higher foam is desired. This surfactant performs best at temperatures below 66C (151F). 

Surfactants are chemical compounds that possess great surface activity. They act so diversely because of the unbalanced molecular structure. A surfactant molecule may be visualized as a tadpole or a mini-racquet. The head is the hydrophilic (water-loving), strongly polar portion and the tail is the hydrophobic (oU-loving) nonpolar portion. The head can be an anion, a cation, or nonion. The tail is a linear or branched hydrocarbon chain. It is this characteristic configuration that makes surfactants perform such diverse function in industry. 

Since surface or interfacial tension reduction depends on the replacement of solvent molecules at the interface by surfactant molecules, the efficiency of a surfactant in reducing surface tension should reflect the concentration of the surfactant at the interface relative to that in the bulk liquid phase. A suitable measure for the efficiency with which a surfactant performs this function would therefore be the ratio of the concentration of surfactant at the surface to that in the bulk liquid phase at equilibrium, both concentrations being expressed in the same units, e.g., [Cj]/Ci, where both concentrations are in moles/liter. 

A clear correlation has been observed between limiting surface tension ycmc and surfactant performance in water-in-C02 microemulsions, as measured by the phase transition pressure Ptnms- These results have important implications for the rational design of C02-philic surfactants. Studies of aqueous solutions are relatively easy to carry out, and surface tension measurements can be used to screen target compounds expected to exhibit enhanced activity in CO2. Therefore, potential surfactant candidates can be identified before making time-consuming phase stability measurements in high-pressure CO2. 

For many of the applications noted in Table 3.2, the desired properties will vary significantly. For that reason, such characteristics as solubility, surface tension reducing capability, critical micelle concentration (cmc), detergency power, wetting control, and foaming capacity may make a given surfactant perform well in some applications and less well in others. The universal surfactant that meets all of the varied needs of surfactant applications has yet to emerge from the industrial or academic laboratory. 

Harwell, J.H., 1992. Factors affecting surfactant performance in groundwater remediation applications. In Subsurface Contaminants, D.A. Sahatini, and R.C. Knox (eds.), Washington, D.C. American Chemical Society, Chap. 10, pp. 124-132. 

Some surfactants perform multiple functions. Reactive surfactants (surfmers) (214,289) chemically react with monomer to become bound at the surface of the particles, and caimot desorb or migrate to the surface of a latex film (44,168). Surfactants may also contain reactive groups that function as initiators (i.e., inisurfs) or chain transfer agents (i.e., transurfs). Anti-foaming agents (defoamers), which are typically silicones or hydrocarbons, may be incorporated in the emulsion recipe to counteract the foaming effects of the surfactant. 

By virtue of their structure, surfactants perform several functions in aqueous solution. Often, however, there are processes in which one uses a surfactant for a desired property and does not want the other properties inherent in the surfactant. For example, one may want detergency without foam. Modihcation of the surfactant molecule offers minimal relief. Consequently, antifoam compounds... 

Builders Reduce water hardness to allow better surfactant performance may provide a good level of alkalinity for cleaning may assist with suspending and preventing soil redeposition Sodium tripolyphosphate Sodium citrate Sodium carbonate Zeolite Nitroltriacetic acid (NTA) Citric acid Tartrate succinate ... 

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