Phase Separation When Adding Sunscreen BEMT to Lotion
Asked by: kamphu_yg
On: March 16, 2022
Product Type:
Cosmetics
Question
Why did adding the sunscreen ingredient BEMT, dissolved in LipidSoft CC, to an existing natural oil-based lotion cause phase separation, and what are the reasons behind this instability?
Answer
Adding sunscreen ingredients like BEMT (Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine) to an existing lotion, especially a natural oil-based one which is likely an emulsion, can indeed cause separation if not done correctly.
Here's why the separation likely occurred:
- BEMT is Oil-Soluble: BEMT is a powder that needs to be dissolved in an oil phase to be incorporated into a formula. LipidSoft CC (Cetyl Ethylhexanoate) is an emollient ester that acts as a suitable solvent for BEMT, with a solubility limit of about 12% BEMT in LipidSoft.
- Emulsion Stability: Lotions are typically emulsions, meaning they are a stable mixture of oil and water phases held together by emulsifiers. When you add an additional oil phase (your BEMT/Lipid Soft CC solution) to an already formed emulsion, you are potentially disrupting the delicate balance between the oil phase, water phase, and emulsifier system.
- Overloading the Emulsifier: The emulsifiers in your original lotion formula were designed to stabilize a specific ratio of oil and water. Adding more oil without adjusting the emulsifier concentration or type can overload the emulsifier system, causing it to fail and the oil and water phases to separate.
- Incompatibility: While LipidSoft CC is a good solvent for BEMT, the combination might not be fully compatible with all the ingredients in your original natural oil-based lotion formula, further contributing to instability.
In summary: The separation was likely caused because your existing lotion formula (an emulsion) was not stable enough to incorporate the additional oil phase containing the dissolved BEMT.
To successfully incorporate BEMT into a lotion, it's generally best to:
- Dissolve the BEMT in the appropriate oil-soluble solvent (like LipidSoft CC) as part of the oil phase before you create the emulsion.
- Formulate the emulsion from scratch, ensuring your emulsifier system is robust enough to handle the total amount of the oil phase, including the BEMT solution.
- If adding to an existing formula is necessary, it might require adjusting the formula by adding more emulsifier or a co-emulsifier, and carefully incorporating the oil phase while maintaining the correct temperature and mixing conditions.
