Essential Ingredients and Steps for Formulating a Physical Sunscreen

Based on the provided ingredient list, a physical sunscreen formulation primarily relies on mineral UV filters like Zinc Oxide and Titanium Dioxide. To create a stable and effective physical sunscreen emulsion, you will need several key components:

Essential Ingredients:

• Water Phase:

  • Water
  • Humectants (e.g., Butylene Glycol, Propanediol, Methylpropanediol, Methyl Gluceth-20, Sodium Hyaluronate) - help hydrate the skin.
  • Water-soluble thickeners/stabilizers (e.g., Xanthan Gum)

• Oil Phase:

  • Emollients/Solvents (e.g., Isododecane, Neopentyl Glycol Diheptanoate, Dimethicone) - provide texture and help disperse UV filters.
  • Oil-soluble emulsifiers (e.g., Glyceryl Stearate and PEG-100 Stearate, Steareth-2, Steareth-21) - help mix the oil and water phases.
  • Physical UV Filters: Micronized Zinc Oxide and Micronized Titanium Dioxide - provide UV protection. These need to be properly dispersed in the oil phase.
  • Oil-soluble antioxidants (e.g., Vitamin E (Tocopheryl Acetate), Ascorbyl Tetraisopalmitate) - help protect the formula and skin.

• Other Key Ingredients:

  • Thickeners/Rheology Modifiers (e.g., Ammonium Acryloyldimethyltaurate/VP Copolymer, Carbomer) - stabilize the emulsion and provide desired texture.
  • Preservatives (e.g., Phenoxyethanol, Caprylhydroxamic Acid) - prevent microbial growth.
  • Neutralizer (e.g., Triethanolamine) - often used to activate thickeners like Carbomer.
  • Functional Additives (e.g., Alumina) - can improve texture and UV filter dispersion.
  • Botanical Extracts (e.g., Saxifrage Sarmentosa Extract) - can provide additional skin benefits.

General Mixing Steps (for an Oil-in-Water emulsion with physical filters):

1. Prepare the Water Phase: Combine water and water-soluble ingredients. Heat this phase to the recommended temperature (usually around 70-75°C).
2. Prepare the Oil Phase: Combine oil-soluble ingredients. In a separate container, disperse the Micronized Zinc Oxide and Micronized Titanium Dioxide into a portion of the oil phase using a high-shear mixer until fully dispersed. Combine this dispersion with the rest of the oil phase and heat to the same temperature as the water phase.
3. Emulsification: Slowly add the heated oil phase (containing the dispersed UV filters) to the heated water phase while mixing continuously with high shear to form a stable emulsion.
4. Cooling: Cool the emulsion while continuing to mix at a moderate speed.
5. Add Heat-Sensitive Ingredients: Once the emulsion has cooled below 40°C, add heat-sensitive ingredients such as preservatives, remaining thickeners (often added as a dispersion or solution), water-soluble antioxidants, humectants, and botanical extracts.
6. Neutralization (if using Carbomer): If using a thickener like Carbomer, add the neutralizer (e.g., Triethanolamine) dropwise while mixing until the desired viscosity is achieved.
7. Final Adjustments: Check and adjust the pH and viscosity of the final product as needed.

Creating a stable physical sunscreen requires careful selection of ingredients, precise measurements, and proper mixing techniques, especially for dispersing the mineral UV filters evenly to ensure effective and consistent UV protection.