ABSTRACT
Outline 386
Introduction 386
Fundamental Requirements 387
Rheology 388
Emulsion Rheology 389
De-Emulsification Behavior 391
Formulating with Organic Sunscreens 391
Oil-Soluble Organic UV Filters 392
Effect of Emulsion Type 392
Effect of Added Emollients 393
Water-Soluble Organic UV Filters 394
Effect of Emulsion Type 394
Effect of Emulsifiers 394
Formulating with Inorganic Sunscreens 394
Basic Principles 394
Formulating with Water-Dispersed TiO2 401
Formulating with Oil-Dispersed TiO2 403
Formulating with Zinc Oxide 404
Combining Sunscreens 404
Combining Organic Sunscreens 405
Combining Inorganic Sunscreens 406
Combining Organic and Inorganic Sunscreens 406
SPF Modulation by External Factors: Water Resistance 406
Fundamental Requirements for Water Resistance 407
Strategies for Water Resistance 408
W/O Emulsions 408 Silicones 408
Specialized Emulsifiers 408
Liquid Crystal Gel Networks 409
Film-Forming Polymers 409
The “Dual-Strategy” Approach 409
Summary 409
References 410
OUTLINE
Formulators of modern sunscreen products are required to meet ever-increasing
demands in terms of product efficacy, both for SPF claims and for broad-spectrum
(UV-A) protection. While it is well known (and intuitively understood) that SPF is
dependent on the type and concentration of UV filters incorporated in a formu-
lation, what is sometimes overlooked is the vital role played by the formulation
itself. This chapter discusses the influence of various aspects of the formulation
on product efficacy, and aims to provide the formulator with the some guiding
principles to optimize the effectiveness of UV filters in finished products.
