Technical Advice on Emulsifiers for O/W Spray

Here is the technical information regarding the use of PEG-40 Hydrogenated Castor Oil and Polysorbate 20 in your Oil-in-Water (O/W) spray formulation with a 15% oil phase (5% Castor Oil, 10% Essential Oil):

1. Suitability and Optimum Oil Phase Concentration

• Both PEG-40 Hydrogenated Castor Oil and Polysorbate 20 are non-ionic emulsifiers and solubilizers suitable for O/W systems.
• A 15% oil phase is a moderate oil load. Using these two emulsifiers together can be effective. PEG-40 Hydrogenated Castor Oil primarily acts as a solubilizer/emulsifier for the essential oil component, while Polysorbate 20 can function as a co-emulsifier.
• There isn't a single "optimum" oil phase concentration for this specific combination, as it depends heavily on the ratio of the two emulsifiers, their total concentration, and the specific oils used. However, this combination is generally suitable for oil phases ranging from approximately 10% to 20%. Achieving a stable, light spray at 15% oil may require careful optimization of the emulsifier ratio and total concentration.

2. Lower Viscosity Alternatives for Spray

• PEG-40 Hydrogenated Castor Oil can contribute some viscosity to the final product, which might not be ideal for a very light spray.
• To achieve lower viscosity, you could consider alternative liquid O/W emulsifiers or solubilizers.
• Examples of alternatives that might offer lower viscosity include PPG-6-Decyltetradeceth-30 or other solubilizers specifically designed for low-viscosity spray formulations, such as Flora Solve Clear (which is mentioned as an alternative solubilizer in the information for Polysorbate 20).
• Note that switching emulsifiers will require testing to ensure compatibility and stability in your specific formula.

3. Shear Tolerance (Homogenization)

• Non-ionic emulsifiers like PEG-40 Hydrogenated Castor Oil and Polysorbate 20 are generally very tolerant to high shear.
• They can safely be processed using a homogenizer. High shear helps to create smaller oil droplets, which typically results in a more stable and finer emulsion suitable for spraying.

4. Alcohol Tolerance (Ethanol)

• Both PEG-40 Hydrogenated Castor Oil and Polysorbate 20 are generally compatible with ethanol.
• They are commonly used in formulations containing alcohol, such as fragrance sprays or other hydro-alcoholic systems.
• Compatibility can depend on the concentration of ethanol and the overall composition of your formula. It is recommended to perform compatibility testing with your specific blend of ingredients.

5. Temperature Tolerance

• Both emulsifiers exhibit good thermal stability.
• They can withstand the temperatures typically used during the emulsification process (commonly around 60-70°C).
• Homogenizing at these elevated temperatures is safe and often beneficial for forming a stable emulsion. Avoid prolonged exposure to temperatures significantly above 80°C, although they can tolerate typical processing heat.

Optimizing the ratio of PEG-40 Hydrogenated Castor Oil and Polysorbate 20, along with their total concentration, will be key to achieving the desired stability and spray characteristics for your 15% oil phase formulation.