Adding Water Resistance to Water-Based Titanium Dioxide Gel Sunscreen

To make your water-based gel sunscreen containing water-dispersible Titanium Dioxide waterproof and prevent white streaks from sweat, you need to incorporate a suitable film former into your formulation. Film formers create a protective layer on the skin that resists water and sweat.

Based on the available ingredients, several water-dispersible film formers could be suitable:

• UV35 (Polyurethane-35): This film former is specifically designed to be water-resistant and can help boost SPF values. It is compatible with both organic and inorganic sunscreens (like Titanium Dioxide) and helps increase durability in water. It is a white liquid and can be used at a rate of 1-10%.
• Allianz OPT (Acrylates/C12-22 Alkyl Methacrylate Copolymer): This polymer provides water and wear resistance and works well in low-viscosity systems like gels and sprays because it doesn't significantly increase viscosity. It is a white sticky liquid used at 1-5%.
• Flex Film (Water Base): This provides moderate water resistance with a soft film texture, suitable for application on the skin. It is a cloudy liquid and can be used at 5-15%.
• Comfort Film (Water Base): While also a water-based film former, its primary benefit is a comfortable, non-sticky feel on the skin, helping products stay on longer. It offers moderate durability but might be less focused on strong water resistance against significant sweating compared to UV35 or Allianz OPT. It is a cloudy liquid used at 5-50%.

For a sunscreen gel aiming for sweat resistance, UV35 or Allianz OPT appear to be the most promising options due to their specific properties related to water resistance and compatibility with gel textures and sunscreen actives. You can add these film formers to the water phase of your formulation.

Your existing water-dispersible Titanium Dioxide, similar to products like WaterMix™ White (Titanium Dioxide 60%, Water-Dispersible Liquid) or Titanium Dioxide Transparent (15nm, Water-Dispersion), should be compatible with these water-based film formers.

It is recommended to experiment with the concentration of the chosen film former, starting with the lower end of the suggested usage rate and adjusting as needed, to achieve the desired level of water resistance without negatively impacting the gel texture or stability with the Titanium Dioxide dispersion.