I’ve created the following guide for solubilizing oils into water to assist you in your formulations. Here, I cover the basics, and give you formulation tips and product suggestions.
Micellar dispersions are the most common type of clear, oil-in-water dispersions using surfactants and/or solvents. If the particle size of the dispersed phase is <100 nm, the dispersion normally appears clear. Typically these dispersions are used to solubilize fragrance oils into water based products and have a particle size of ~5nm.
- Generally, more polar oils are easier to solubilize into water and require less surfactant. For example, 10 grams of Polysorbate 20 can solubilize ~1-3 grams of fragrance oils and only .1-.3g of non-polar oils.
(EU: Polysorbate 20)
- When solubilizing most oils, start with a ratio of 10 parts solubilizer to 1 part oil and titrate down. For fragrances, start with 5 parts solubilizer to 1 part fragrance oil.
- Liquid solubilizers are preferred vs. solid types due to ease of processing.
(EU: Liquid solubilizers)
- Water soluble solvents, in which the oil dissolves, can help reduce the amount of solubilizer needed.
- Solvents can usually help reduce the amount of solubilizer needed. 1, 2 hexanediol is by far the best, followed by 1, 2 pentanediol, diethylene glycol mono ethyl ether, and dimethyl isosorbide.
(EU: 1, 2 hexanediol | 1, 2 pentanediol | dimethyl isosorbide)
- Use combinations of solubilizers for better efficiency. Many of the most efficient ones are surfactant blends.
- Monitor the particle size distribution changes (sub-micron particle size analyzer) over time using clarity loss or particle size changes as endpoints.
- Generally, a loss in clarity or particle size change over time can be caused by Ostwald Ripening. Adding a small amount of nonpolar oil or a polymeric surfactant can be helpful to minimize the problem.
- The key historic benchmark solubilizer is PEG 40 Hydrogenated Castor Oil (Cremophor RH 40 – BASF) (EU: PEG 40 Hydrogenated Castor Oil)
- Eumulgin HPS (PEG-40 Hydrogenated Castor Oil, PPG-1-PEG-9 Lauryl Glycol Ether – BASF, Coceth 7 – BASF) (EU: Eumulgin HPS)
- Cosmacol N119 (C12-C13 Pareth 9-Sasol) Recommended green options not containing ethylene oxide based surfactants
- Sophogreen (Water, Glucose, Rapeseed Fatty Acid-Soliance)
- Sepiclear G7 (Heptyl Glucoside-Seppic)
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