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Evaporation of Sunscreen Films: How the UV Protection Properties Change

Binks, Bernard P.; Brown, Jonathan; Fletcher, Paul D.I.; Johnson, Andrew J.; Marinopoulos, Ioannis; Crowther, Jonathan M.; Thompson, Michael A.

Authors

Jonathan Brown

Paul D.I. Fletcher

Andrew J. Johnson

Ioannis Marinopoulos

Jonathan M. Crowther

Michael A. Thompson



Abstract

© 2016 American Chemical Society. We have investigated the evaporation of thin sunscreen films and how the light absorption and the derived sun protection factor (SPF) change. For films consisting of solutions of common UV filters in propylene glycol (PG) as solvent, we show how evaporation generally causes three effects. First, the film area can decrease by dewetting leading to a transient increase in the average film thickness. Second, the film thins by evaporative loss of the solvent. Third, precipitation of the UV filter occurs when solvent loss causes the solubility limit to be reached. These evaporation-induced changes cause the UV absorbance of the film to decrease with resultant loss of SPF over the time scale of the evaporation. We derive an approximate model which accounts semiquantitatively for the variation of SPF with evaporation. Experimental results for solutions of different UV filters on quartz, different skin mimicking substrates, films with added nanoparticles, films with an added polymer and films with fast-evaporating decane as solvent (instead of slow evaporating PG) are discussed and compared with model calculations. Addition of either nanoparticles or polymer suppress film dewetting. Overall, it is hoped that the understanding gained about the mechanisms whereby film evaporation affects the SPF will provide useful guidance for the formulation of more effective sunscreens.

Journal Article Type Article
Publication Date May 11, 2016
Journal ACS applied materials & interfaces
Print ISSN 1944-8244
Electronic ISSN 1944-8252
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 8
Issue 21
Pages 13270-13281
Institution Citation Binks, B. P., Brown, J., Fletcher, P. D., Johnson, A. J., Marinopoulos, I., Crowther, J. M., & Thompson, M. A. (2016). Evaporation of Sunscreen Films: How the UV Protection Properties Change. ACS applied materials & interfaces, 8(21), 13270-13281. https://doi.org/10.1021/acsami.6b02696
DOI https://doi.org/10.1021/acsami.6b02696
Keywords Sunscreen, Evaporation, Spectrophotometry, Precipitation, Wetting, Sun protection factor
Publisher URL http://pubs.acs.org/doi/abs/10.1021/acsami.6b02696
Additional Information This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS applied materials & interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acsami.6b02696

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