SUN CARE It should be strongly emphasised that
particle size result is variable based on the technique that is used for the analysis. The technique used in this analysis was to disperse the zinc oxide sample in water with a dispersing agent. The concentration of the dispersion is a function of the Bettersize 9300-S’s ability to detect the sample being analysed. Microscopic techniques, such as SEM
and TEM, can also be used to quantify the particle size. Although, again, a different set of numbers was obtained, the trend from smallest to largest particle size remains constant independent of the analytical technique used to determine it.
Conclusion Because the focus of this article is not on determination of particle size but sunscreen UV filters, it will be left that, independent of particle size analytical technique, the data concludes directionally there is a trend correlating the particle size of the zinc oxide powder with the final viscosity of the sunscreen. The primary use of this finding is that a formulator may be able to eliminate a thickening agent, an inactive ingredient, by using zinc oxide, a broad-spectrum UV filter. An experienced formulator will know how
to manipulate a sunscreen formulation to get the desired aesthetics. As the demand for more natural and environmentally safe products grows every year, the advantages of zinc oxide as a UV filter in sunscreens sets it apart. It is classified by the FDA as GRASE. As long as it is
TABLE 4: NATURALLY DERIVED SPF 15 ZINC OXIDE-BASED SUNSCREEN FORMULATION
Sequence 1
1
1 1
2 3 3 3 4
Ingredient Plant based emollient
70% Naturally derived emollient
Emulsifier, 98% naturally derived
Natural dispersing agent Zinc oxide
Solvent (deionized water) Preservative
Emulsion stabilizer pH adjuster
%
20 15
15 1
10
37.5 1
0.5 as needed
not nanoparticle zinc oxide, it is also recognised as being reef-safe and therefore environmentally the right choice for a UV filter. As shown in this article, a formulator has the
ability to modify the finished viscosity of the sunscreen without changing the SPF value by selecting zinc oxides with varying particle sizes and potentially eliminating the need for viscosity modifiers.
109
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4. Boerner L.K What’s in sunscreen, and how does it protect your skin from the sun’s rays? Chemical & Engineering News. 2021 Jul 21, 99(27)
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https://www.cosmeticsdesign-
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www.personalcaremagazine.com
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