Results from a formulation case study are presented to show how information from rheological studies can be utilized to help characterize a complex emulsion system. Viscoelastic rheological behaviors in conjunction with In Vitro SPF testing are studied to optimize a multi-component sunscreen emulsion formulation. Data from amplitude sweeps, flow curves, and dynamic frequency tests from an Anton Par Physica 301 Rheometer are discussed with corresponding SPF results generated from a Labsphere UV Transmittance Analyzer. Microscope pictures are presented to verify findings and provide a visual understanding of the results.

More specifically, the data generated was used to characterize the effects of a polymeric substance that varied in molecular weight and degree of ethoxylation. Examination of concentration dependence and comparison to appropriate controls in the experimental design enabled selection of the appropriate polymeric substance to be incorporated into a sunscreen emulsion composition that provided the highest SPF value. The ethoxylated polymeric materials had no inherent UV absorbing capability and had no affect on particle size at the low concentration levels in this investigation. Yet, not only did these ethoxylated polymeric substances increase the efficiency of the sunscreen filter system, one of the polymeric substances behaved in a synergistic manner causing a significant increase in the In-Vitro SPF.