A typical plot of the surface tension of a 1% SLS (sodium lauryl sulfate) solution with varying amounts of silicone surfactant added is shown in Figure 4. Although no clear break point is observed for pure surfactants at critical micelle concentration, Figure 4 does resemble the surface tension diagram of surfactants. The ability to change the shape of the curve is critical to the economics of surface tension reduction. The curve is concave; the desired curve is convex, using minimal silicone (“silicone greening”) to produce lower surface tension. Since a clear critical micelle concentration cannot be determined. The lower the RF50, the stronger the ability of the silicone surfactant to compete with the fatty surfactant for surface, and the more effective the silicone surfactant is. This technology allows one to design molecules optimized for specific formulations. By simply defining the surface tension of a fatty surfactant as the initial surface tension of the formulation, not only surfactant systems but also complex formulations can be evaluated. By evaluating the properties of the foam rather than the surface tension, it is not only possible to test and optimize foam, but also foam and more. Table 1 lists the RF50 values for specific combinations. The so-called RF50 value is a measure of the effectiveness of reducing surface tension in a mixing system. The lower the RF50 value, the lower the concentration required to reduce the surface tension between the two surfactants in the mixed system by 50%. The ability to reduce surface tension depends on the type of oil chosen and how it interacts with the added alkylsiloxane. The low molecular weight silicone ethylmethicone is more effective at reducing surface tension than the cetylmethicone found in olive oil. Ethylsimethicone in olive oil has an RF50 of 2%, while cetylsimethicone in olive oil has an RF50 of 8%. Figures 5 and 6 show the RF50 values.
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