JOURNAL OF COSMETIC SCIENCE 220 this theory, two separate fi lms were prepared on PMMA plates. On the fi rst plate, a 2% solution of the polymer was applied fi rst, followed by the control formula. On the second plate, the control formula was applied fi rst, followed by the polymeric solution. The plates were left to dry for 15 minutes and their absorbance was measured in vitro. The data are presented in Figure 5. As seen in the graph, when the polymer was applied fi rst, the boosting effect was lower than when it was applied last, indicating that the polymeric fi lm being formed is typically forming over the sunscreen. It is also interesting to see that the highest boost was achieved by the test formula. The addition of the polymer over a layer of sunscreen may not allow the polymer to orient itself properly in the fi lm to give the highest boosting, as compared to when the polymer is incorporated in the actual for- mulation. The data obtained suggests that the polymer forms a protective fi lm over the sunscreen fi lm with a different refractive index. As a result, the increased pathlength of the incident UV light over the fi lm causes an increase in SPF. Figure 4. Self-adapting technology. RF1 and RF2 refer to two different refractive indices. The values 63 and 72 are contact angles obtained for the fi lms before and after immersion. Figure 5. Effect of order of addition of the polymer on SPF boosting.

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