*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.