Film Former Recommendation for Waterproof Physical Sunscreen

For a physical sunscreen formula requiring excellent water resistance for swimming in the sea, choosing the right film former is crucial. Film formers help create a protective film on the skin, allowing the sunscreen to adhere better and resist washing off when exposed to water for extended periods. Based on the available information, several film formers are suitable for this application:

• Silicone Film Group (Trimethylsiloxysilicate based):

  • Silicone Film (Very Long-Wear, Hard, Isododecane Base) and Silicone Film (Very Long-Wear, Hard, Cyclopentasiloxane Base): These provide a hard, exceptionally long-lasting film, ideal for formulas requiring maximum durability. Recommended usage rate is 5-30%, mixed into the silicone or oil phase.
  • Silicone Film (Soft Film, Low Viscosity, Isododecane Base) and Silicone Film (Soft Film, Low Viscosity, Cyclopentasiloxane Base): This group offers a softer film texture while still providing good durability and waterproofing. Usage rate is 1-30%, mixed into the silicone or Isododecane/Isohexadecane phase.
  • Silicone Film (Smart-Wear, Hard, Cyclopentasiloxane Base): Provides a long-lasting film that is also comfortable on the skin. Suitable for formulas balancing durability and comfort. Usage rate is 5-30%, mixed into the silicone or oil phase.

• Ethylcarbamate Film (58% in Isododecane, Low Viscosity/Low Stickiness): This Silicone Polyurethane is described as the "most persistent" type of film, lasting over 8 hours. It forms a soft film that adheres very well to the skin. Suitable for formulas where silicone or Isododecane/Isohexadecane is the main component. Usage rate is 1-10%.

• Vinyl Film (Medium Wear, Soft) (VP/Hexadecene Copolymer): Forms a waterproof film and helps formulas last longer. It also aids in pigment dispersion, making it suitable for sunscreens to enhance water and sweat resistance. Usage rate is 1-10%, mixed into the oil phase.

• Water-dispersible Polymer Group:

  • Syntran 5778 and Syntran 5288: These are water-dispersible film formers offering long-lasting and waterproof properties. They are suitable for emulsion or water-based formulas. Usage rate is relatively high at 10-70%, mixed into the water phase.
  • Allianz OPT (Acrylates/C12-22 Alkyl Methacrylate Copolymer): This polymer film former provides water and wear resistance for long-lasting sun formulas. It works well in low viscosity emulsions, spray sunscreens, and gels. Usage rate is 1-5%, dispersible in water.

In Summary:

If your formula is oil or silicone-based and requires very long-lasting water resistance, consider the Silicone Film (Trimethylsiloxysilicate based) group, especially the "Very Long-Wear" types, or Ethylcarbamate Film, or Vinyl Film.

If your formula is an emulsion or water-based, the Water-dispersible Polymer group like Syntran 5778, Syntran 5288, or Allianz OPT would be suitable.

The best choice depends on your formula's base (oil/silicone or water/emulsion), the desired level of durability, and the preferred film texture. It is recommended to test in your specific formula to determine the most effective option.