The Economic Importance of Surfactants

TABLE 1.1. Typical (But Not All) Characteristics for Surfactants that Must Be Evaluated for Various Applications 

Low cmc, good salt and pH stability, biodegradability, desirable foaming properties 

Proper wetting of oil-bearing formations, microemulsion formation and solubilization properties, ease of emulsion breaking after oil recovery 

Economic considerations can often be almost as important as surface activity in selecting a surfactant for a given appUcation. Unless the cost of the surfactant is insignificant compared to the rest of the system, the least expensive material producing the desired effect will usually be chosen. Economics, however, cannot be the only factor in the choice, since the final performance of the system may well be of crucial importance. To make a rational selection, without resorting to an expensive and time-consuming trial-and-error approach, the formulator should have some knowledge of (1) the surface and interfacial phenomena that must be controlled (2) the characteristic chemical and physical properties of the available surfactant choices (3) the relationships between the structural properties of the available surfactants and their effects on the pertinent interfadal phenomena (4) any restrictions to the use of available materials, as in, for example, foods, cosmetics, or pharmaceuticals and (5) economic constraints on the choice of surfactant. 

The applications of surfactants in science and industry are legion, ranging from primary processes such as the recovery and purification of raw materials in the mining and petroleum industries, to enhancing the quality of finished products such as paints, cosmetics, pharmaceuticals, and foods. Table 3.2 lists some of their major areas of application. As the technological and legal demands placed on products and process additives such as surfactants increase, it seems obvious that our need to understand the relationships between the chemical structures of those materials and their physical manifestations in particular circumstances becomes more important. 

TABLE 3.2. Some of the Major Modem AppHcations of Surfactants 

Lubrication Mold release agents Ore flotation Paper manufacture Petroleum recovery Printing and printing inks Surface preparations Textiles Waterproofing Waxes and polishes 

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. 

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