Incorporating Film Formers in W/O Water-Resistant Sunscreen: Phase and Temperature
Asked by: mondodariofficial
On: November 10, 2025
Product Type:
Cosmetics
Question
I am developing a water-resistant sunscreen cream using a Water-in-Oil (W/O) system. I need guidance on the proper procedure for incorporating specific film formers.
- At what step in the mixing process (before emulsification, after emulsification, or during cooling) should the film formers be added?
- What is the appropriate temperature for adding these components?
The film formers I plan to use are:
VP/Hexadecene Copolymer(intended for the oil base)Isododecane (Germany)+UV35 (Polyurethane-35)(intended for the water base)
Should these components be mixed in after the emulsification step?
Answer
The general procedure for incorporating film formers in a hot-process Water-in-Oil (W/O) sunscreen is to add them to their respective phases (oil or water) before the emulsification step.
1. Temperature
- Heat both the Oil Phase (A) and the Water Phase (B) to the standard emulsification temperature, typically 70-80°C. This ensures all components, including the film formers, are fully dissolved or dispersed.
2. Addition Step (Before Emulsification)
| Film Former | Solubility | Recommended Phase | Addition Temperature |
|---|---|---|---|
| VP/Hexadecene Copolymer | Oil-soluble | Oil Phase (A) | 70-80°C (Heat until fully dissolved) |
| UV35 (Polyurethane-35) | Water-dispersible | Water Phase (B) | 70-80°C (Heat until fully dispersed) |
| Isododecane | Oil-soluble (Volatile Solvent) | Oil Phase (A) or Cooling Phase (C) | 70-80°C (if in A) or Below 40°C (if in C) |
- VP/Hexadecene Copolymer: Add this to the Oil Phase (A) along with other oils, emulsifiers, and oil-soluble UV filters. Heat this phase to 70-80°C until the copolymer is fully dissolved.
- UV35 (Polyurethane-35): Add this to the Water Phase (B) along with water and other water-soluble ingredients. Heat this phase to 70-80°C until it is fully dispersed/dissolved.
- Isododecane: While it is an oil-soluble component and can be added to the Oil Phase (A) and heated, it is a volatile solvent. To minimize evaporation and improve the final texture, it is a common practice to add volatile solvents like Isododecane in the Cooling Phase (Phase C), once the emulsion has formed and the temperature has dropped below 40°C.
3. Emulsification
- Once both phases are at the target temperature (70-80°C), slowly add the Water Phase (B) to the Oil Phase (A) while mixing with high shear.
4. Note on Isododecane + UV35
- Isododecane is an oil-soluble solvent and cannot be mixed with the water-dispersible UV35 in the water phase. Please ensure you are adding each component to its correct phase based on its solubility. If you are using a pre-mixed dispersion, follow the supplier's instructions.
Related Products Mentioned
UV35 (Polyurethane-35)
Cosmetics