Nanostructured Surface Treatment Enables the Combination of Nano-particulate ZnO and TiO2 with Acrylate-based Polymers in Cosmetic Formulations
V. Andre and R.W. Brotzman Jr
Nanophase Technologies, US
zinc oxide, titania, UV-protection, cosmetic, acrylate
Modern skin care formulations must meet high standards of efficacy, skin compatibility and aesthetic appeal. The performance of a cosmetic product is related to the entire formulation and an optimal galenic formulation that incorporates a UV-platform is a necessary prerequisite to succeed in the market.
ZnO and TiO2 are active ingredients in OTC suncare product. However problems are encountered when particulate zinc oxide and titania, particularly nano-particulate zinc and titania oxide, are formulated with charged organic moieties, such as acrylate-based polymers, α- and β-hydroxy acids, etc. Contemporary skin care formulations are emulsions – charged organic moieties reside in the aqueous phase and the active inorganic ingredients reside in the oil phase. In formulation the acrylate-based polymers, once neutralized, chain extend to thicken the formulation by increasing the viscosity of the aqueous phase. Other charged organic moieties, such as α- and β-hydroxy acids, may have other functions such as enhancing epithelial cell regeneration.
However zinc ions from the particulate zinc oxide migrate from the oil phase to the aqueous phase and adversely interact with the charged organic moieties to either cause collapse of the acrylate-based polymers, or induce the formation of organic salts with concomitant dissolution of the particulate inorganic. This instability is accentuated by titania.
A new nanostructured surface treatment was designed to passivate ZnO and TiO2 enabling the combination to be used in formulations containing charged organic moieties. The surface treatment is comprised of a star-graft siloxane copolymer containing looped structures. This surface treatment enables the formulation of elegant skincare products.
The nano-structured surface treatment will be described, formulation guidance given, and formulation efficacy will be compared with state-of-the-art products.
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Nanotech 2006 Conference Program Abstract