Synergism surface tension reduction

The conditions for synergism in surface tension reduction efficiency, mixed micelle formation, and Surface tension reduction effectiveness in aqueous solution have been derived mathematically together with the properties of the surfactant mixture at the point of maximum synergism. This treatment has been extended to liquid-liquid (aqueous solution/hydrocarbon) systems at low surfactant concentrations.) The effect of chemical structure and molecular environment on the value of B is demonstrated and discussed. 

Synergism in surface tension reduction efficiency. The efficiency of surface tension reduction by a surfactant is defined (9) as the solution phase concentration required to produce a given surface tension (reduction). Synergism in this respect is present in a binary mixture of surfactants when a given surface tension (reduction) can be attained at a total mixed surfactant concentration lower than that required of either surfactant by itself. This is illustrated in Figure 2. 

Figure 2. Synergism in surface tension reduction efficiency (Ci2 < C ° or 2°) or in mixed micelle formation...

Table I. Synergism in Surface Tension Reduction Efficiency ...

By mathematical treatment similar to that for synergism in surface tension reduction efficiency, we have found that the conditions for synergism in mixed micelle formation are ... 

Synergism in surface tension reduction effectiveness. This exists when the mixture of surfactants of its cmc reaches a lower surface tension than that obtained at the cmc of either component of the mixture by Itself. This is illustrated in Figure 5. 

Figure 5. Synergism in surface tension reduction effectiveness. (Ycmc 2 Y°cmc or Y°cmC2). (l) Pure surfactant 1 ...

From the relations upon which equations 11.1 and 11.2 are based and the definition for synergism or antagonism (negative synergism) of this type, it has been shown mathematically (Hua, 1982b, 1988) that the conditions for synergism or antagonism, in surface tension reduction efficiency to exist are ... 

It is apparent from condition 1 that synergism in surface tension reduction effectiveness can occur only when the attractive interaction between the two surfactants in the mixed monolayer at the aqueous solution-air interface is stronger than that in the mixed micelle in the solution phase. When the attraction between... 

Surfactants C and D of Problem 2 individually reduce the surface tension of an aqueous 0.1 M NaCl solution to 30 dyn/cm when their respective molar concentrations are 9.1 x 10 4 and 3.98 x 10-4. The mixture of them at a = 0.181 in Problem 2 has a surface tension value of 30 dyn/cm when the total molar surfactant concentration is 3.47 x 10-4. Will a mixture of surfactants C and D exhibit synergism or antagonism in surface tension reduction effectiveness ... 

Fig. 2 Synergism in surface tension reduction efficiency or in mixed micelle formation. Surfactant 1. Surfactant 2. 0 Mixture of surfactants 1 and 2 at mole fraction a in the solution phase. Synergism in surface tension reduction efficiency Cn < C , C . Synergism in mixed micelle formation < CT, Cf...

The first condition means that the two surfactants must have an attraction for each other the second that this attraction must be stronger than the difference between the natural logarithms of the two concentrations needed to produce this same surface tension (reduction) of the solvent. Therefore, to maximize this type of synergism, two materials with strong attraction for each other (large negative P° value) should be used. 

To obtain maximum synergism in surface tension reduction efficiency, the two surfactants should be used at a mole fraction, a (of surfactant 1 in the total surfactant in the solution phase), given by the expression... 

III.C. Synergism or Antagonism (Negative Synergism) in Surface or Interfacial Tension Reduction Effectiveness... 

At the point of maximum synergism or maximum antagonism in surface or interfacial tension reduction effectiveness, the composition of the mixed interfacial layer equals the composition of the mixed micelle, i.e., X E = the mole... 

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