Titanium dioxide is sometimes described as a “natural sunscreen” because it is derived from a naturally occurring mineral. However, to make it suitable for use as a sunscreen, several chemical processes must be completed, including the application of organic and/or inorganic coatings.
As a sunscreen agent, attenuation-grade titanium dioxide with much smaller primary particle sizes than pigmentary-grade TiO2 must be used to minimize skin whitening. These very small primary particles tend to aggregate more than tenfold, and powders supplied frequently contain aggregates over one micron.
Therefore, proper grinding is necessary. With optimal grinding conditions, smaller primary particle (10-15nm) size Titanium dioxide always provides better transparency and UVB protection. In comparison, TiO2 of a larger primary particle (35nm) size will give better UVA protection. Therefore, the selection of Titanium dioxide will be based on the SPF and PFA values intended for the finished formula, as well as the use level.
The surface activity of attenuation grade Titanium dioxide, either its photo-catalytic activity or chemical activity towards other ingredients like vitamin C and Avobenzone in the formula, must be considered. Larger-size TiO2 has a smaller surface area and also can be readily coated, making the particle very stable. Surface-treating micronized Titanium dioxide has been shown to make it less reactive and a new heavy-coated, 15nm TiO2.Ingredients
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