Surface tension synergism

A mixture of Zonyl FSN, a nonionic fluorinated surfactant, and Tergitol NP-10, a nonionic hydrocarbon-type surfactant (nonylphenol with 10 oxyethylene units Union Carbide Corp.), exhibited surface tension synergism (Fig. 4.29). The dynamic surface tension of the 1 1 mixture is lower than the dynamic surface tension of the individual components. 

CMCs of LAS-AOS mixtures in water that contained no calcium or magnesium ions were determined by Suri et al. [3] by means of the surface tension method. The purpose of this work was to study the advantage of LAS-AOS synergism in prototype phosphate-free carbonate-built formulations for use in the Indian market. The authors have used a commercial C10-C14 LAS sample with an average molecular weight of 343 and a commercial C16-C18 AOS sample with an average molecular weight of 350. 

The results for the mixture of C qE and C 2A0 are given in figure 5 and suggest possible synergism in the surface tension behavior for this system, which exhibits nearly ideal mixed cmc behavior. Clear evidence of such synergism is seen for the nonideal mixture of and SDS in figure 6. Here, a substan-... 

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 ...

Head louse infestations periodically cause disruptions at schools aii over the world. The treatment with pyrethrins and PBO is relatively cheap, and effective. The most common formulations contain either 0.15% or 0,3% pyrethrins synergized with 3.0% PBO formulated into non foaming shampoos (water- based pm-sized emulsions) that are applied directly to the affected area and repeated after i week to kill any newly hatched lice. The pediculicidal and ovicidal efficacy of synergized pyrethrins arc enhanced in shampoo formulations as a result of the surface-tension-lowering action of the formulation and are preferable to direct applications of lotions. 

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 ... 

At the point of maximum synergism or maximum antagonism, i.e., at the minimum or maximum aqueous phase total molar concentration, respectively, of mixed surfactant to produce a given surface tension, the mole fraction a of surfactant 1 in the solution phase (on a surfactant-only basis) equals its mole fraction X at the interface and is given by the relation. 

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 ... 

PLA/poly(vinyl acetate) (PVAc) blends have been reported by Gajria et al. regarding their miscibility, physical properties, degradation and surface tension. The blends show a miscible phase, and the mechanical properties of the blends exhibit a synergism in the range of 5 to 30% PVAc content. However, the addition of PVAc to PLA leads to a dramatic decrease in the degradation rate for enzymatic degradation. On the contrary, the nonenzymatic and enzymatic hydrolysis of PLA is accelerated by the presence of the hydrophilic PVA, but these blends is... 

In addition to the critical micelle concentration, surface tension versus concentration measurements can give additional information on the (1) efficiency and effectiveness of a surfactant, (2) area a surfactant occupies, (3) synergism or extent of interaction between two surfactants. 

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... 

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