Traditional mineral sunscreens are well-known to provide broad-spectrum protection against both UVA and UVB rays by physically blocking and reflecting sunlight. Despite their many benefits, there is still some reluctance among consumers due to their dense textures, oily after-feel, and the tendency to provide a white cast on the skin. These sensory limitations can affect product desirability and user satisfaction across diverse global markets.

To meet these evolving demands, acrylate-based rheology modifiers such as Pemulen™ EZ-4U, Carbopol® Aqua SF-1 OS or Novemer™ CS polymers play a crucial role in transforming oil-in-water (o/w) mineral-based sunscreens into appealing, fresh, and functional formulations. By enhancing texture, spreadability, and skin feel, these ingredients help deliver lightweight, non-greasy finishes and watery sensations that resonate with today’s consumer needs.

Formulating oil-in-water sunscreens with mineral UV filters such as Zinc Oxide (ZnO) and Titanium Dioxide (TiO₂) presents several challenges. These particles are typically dispersed in the oil phase, which is the smaller portion of the emulsion, making uniform dispersion critical to ensure consistent UV protection and to prevent agglomeration or sedimentation. ZnO, being highly hydrophilic, tends to migrate into the aqueous phase, potentially destabilizing the emulsion. This becomes particularly problematic when acrylic acid-based polymers are used, as they may interact with Zn²⁺ ions, leading to increased viscosity and pH, as well as undesirable textures like grainy, rubbery, or “cottage cheese”-like appearances. TiO₂ compatibility also depends on its coating, especially when aluminum-coated grades are involved. These can interfere with the polymer matrix, causing emulsion instability or gelation, resulting in “cheesecake” textures.

To address these formulation challenges, specific strategies can be applied.

In the oil phase:

Increase affinity of ZnO or TiO2 for the oil phase with a coated version
To effectively separate the agglomeration of these particles and significantly decrease the viscosity of dispersions, Matrifuse™ S-1 dispersant is the preferred choice. In combination with emollients such as Schercemol™ 318, NGDO or CATC esters, it allows higher particles loading, enhancing homogeneity, and boosting product sensory.

In O/W interphase:

Reinforce the oil-in-water interphase to avoid ion migration by incorporating non-ionic emulsifiers to stabilize the emulsion such as Glucate™ SS or Glucamate™ SSE-20 emulsifiers.

In the water phase:

Combine your selected acrylate-based polymer with Kelco Care™ diutan gum or PemuPur START™ polymer to protect the acrylate groups from the interaction with metallic ions.
Incorporate suitable chelating agents and ensure pH is kept within the 6.0-8.0 range.

The use of these strategies supported by Lubrizol ingredients can make a huge difference in the obtention of stable, lightweight and sensory appealing mineral-based sunscreens.

Creating Appealing and Stable Mineral SPF Sunscreens