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 polymerzinc 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 500nm and its structure consists of a dense aggregate of nano-ZnO having a size distribution in the 5-10nm 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.
