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.

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.

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

• Journal Article Type: Article
• Acceptance Date: May 11, 2016
• Online Publication Date: May 18, 2016
• Publication Date: May 11, 2016
• Deposit Date: May 16, 2016
• Publicly Available Date: May 16, 2016
• Journal: ACS applied materials & interfaces
• Print ISSN: 1944-8244
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 8
• Issue: 21
• Pages: 13270-13281
• DOI: https://doi.org/10.1021/acsami.6b02696
• Keywords: Sunscreen, Evaporation, Spectrophotometry, Precipitation, Wetting, Sun protection factor
• Public URL: https://hull-repository.worktribe.com/output/438177
• 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
• Contract Date: May 16, 2016