Low-surfactant Emulsification: Optimizing Formulas and Conserving Resources*

Aug 1, 2010 | Contact Author | By: T. Joseph Lin, PhD
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Title: Low-surfactant Emulsification: Optimizing Formulas and Conserving Resources*
emulsificationx process variablesx surfactantx solubilizationx phase inversionx
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Keywords: emulsification | process variables | surfactant | solubilization | phase inversion

Abstract: Understanding the process variables that occur during emulsion manufacturing can assist formulators in preventing production inconsistencies as well as selecting the most effective surfactant blend for a given purpose. This in turn reduces the amount of surfactant required without affecting emulsion quality or stability, thus saving resources and even improving product quality, as the present article describes.

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TJ Lin, Low-surfactant emulsification: Optimizing formulas and Conserving resources*, Cosm & Toil 125(8) 34-40 (Aug 2010)

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*Adapted from T. Joseph Lin, PhD, Manufacturing Cosmetic Emulsions: Pragmatic Troubleshooting and Energy Conservation, Allured Business Media: Carol Stream, IL USA ch 16 (2010)

The quality of an emulsion, including its stability, is dependent not only upon the delicate balance of ingredients in the formulation, but also on process variables (pVs) that occur during manufacturing. For example, although sufficient mixing assures good stability in most emulsions, longer or more intense mixing does not necessarily produce a higher quality or more stable emulsion; in fact, many emulsions become unstable and deteriorate after intense mixing with a homogenizer.

Such degradation can be attributed to a breakdown in the yield value of the emulsion or unintended phase inversion caused by high shear. Therefore, understanding pVs can be valuable to prevent potential manufacturing issues. It can also assist formulators in selecting the most effective surfactant blend for a given purpose, which in turn can reduce the amount of surfactant required without affecting the emulsion quality or stability. This saves resources and can even improve product quality, as the present article describes.


Lab Practical: Optimizing Formulas

  • Adding the surfactant to aqueous phase increases viscosity and stability.
  • To produce rapid cooling, the alpha phase can be added near the PIT.
  • An inverted primary emulsion forms when the surfactant is initially placed in teh oil phase; with mixing, it fragments, forming a double emulsion that may be more stable.
  • The maximum amount of water possibly solubilized by an oil phase containing surfactants can determine the point of maximum emulsification efficiency.

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Figure 1. Illustration of Mechanism A

Figure 1. Illustration of Mechanism A

Mechanism A involves the formation of an inverted primary emulsion—when an o/w emulsion is prepared by initially placing the surfactant in the oil phase.

Figure 2. W/O/W emulsion from Mechanism A

Figure 2. Microphotograph of a w/o/w emulsion from Mechanism A

Frequently, the double emulsion may be stable and the final emulsion can contain a substantial portion of double emulsion droplets, similar to those shown here.

Figure 3. Illustration of Mechanism B

Figure 3. Illustration of <em>Mechanism B</em>

Mechanism B occurs when all the surfactant is initially placed in the water phase.

Figure 4. O/W emulsion from Mechanism B

Figure 4. Illustration of an o/w emulsion from <em>Mechanism B</em>

Illustration of an emulsion prepared using Mechanism B without the phase inversion process

Figure 5. Solubilization

Figure 5. Solubilization

Solubilization—emulsion droplet size correlation for binary surfactant system; determination of an optimum surfactant blend of two nonionic surfactants

Figure 6. Shifting of optimum emulsification peak

Figure 6. Shifting of optimum emulsification peak

Shifting of optimum emulsification peak by addition of lauryl alcohol; this method accurately predicts the shift in optimum emulsification peak while the HLB method failed to predict this shift.

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