No. 4 Vol. 42, No. 2, pp. 102–109, 2008 A novel water-based sunscreen gel using a polymer – zinc oxide composite |
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Authors: | Eiji Takahashi,Tetsuya Oikawa,Hirokazu Iyanagi,Kunihiko Mohri, Katsuhiko Nakamae&dagger |
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Affiliation: | R&D Department, POLA Chemical Industries, Inc., 27-1, Takashimadai, Kanagawa-ku, Yokohama 221-0833, Japan and Japan Synchrotron Radiation Research Institute, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan |
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Abstract: | Conventional sunscreen products generally must strike a compromise between efficacy and product feel; the hydrophobic ingredients that provide the sun protection generally impart an unpleasant, greasy feel and the greater the SPF rating, the worse the greasy feel. We tested an idea that a water-based sunscreen gel formulation containing inorganic UV absorbers would provide an effective way to address these problems. Our goal was to find a way to disperse inorganic sunscreen materials in water and to incorporate them into a water-based gel which would provide a more pleasant product feel. After extensive research we discovered a polymer-zinc oxide composite (P-ZnO) with high UV protective effect and high dispersibility in water. In dried powdered form, P-ZnO can be easily dispersed in water. P-ZnO makes it possible to formulate a gel-type sunscreen, which is not possible using commercially available inorganic powders. The composite size of P-ZnO is about 500 nm and its structure consists of a dense aggregate of nano-ZnO having a size distribution in the 5–10 nm range and amorphous layers of poly acrylic acid coating zinc oxide to control the particle growth, block surface activity and prevent aggregation. The water-based P-ZnO sunscreen gel offers UV protection comparable to conventional products in a delivery vehicle that is much more pleasant to use. |
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Keywords: | composite efficacy inorganic nano polymer product feel sunscreen UV absorbers water-based gel zinc oxide |
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