Encouraging a double application of sunscreen will help users apply products at a thickness sufficient to achieve expected SPF efficacy. We recommend that guidance on double application of sunscreen should be posted in public locations where sunscreen is likely to be in use.
Surfactant molecules self-assemble to form various microstructures such as spherical micelle, wormlike micelle and hexagonal liquid crystals. Viscoelastic wormlike micelles have drawn considerable interest in basic research and practical applications. Long-chain cationic surfactants like hexadecyltrimethyl ammonium bromide (CTAB)(1-6) and hexadecylpyridinium chlo-ride (7-11) are well known for the formation of wormlike micelles upon addition of counter ions like salicylate or bromide ions. Above some critical concentration, called overlapping concentration, wormlike micelles entangle with each other to form a transient network and exhibit viscoelastic properties (12), analogous to that observed in flexible polymer solution.Recently, viscoelastic solution of wormlike micelles has been reported to form on adding lipophilic nonionic 599 JOS
Surfactants are extensively used in various applications such as detergents and household cleanser, cosmetics as well as in industrial processes. Therefore, there is a growing concern over the impact of the surfactants on the environment as well as human body. Similarly, biocompatibility is another important factor in the selection of surfactants in various applications, especially in the formulation of cosmetics and personal healthcare products. Polyoxyethylene sterol surfactants consist of either cholesterol or phytosterol as lipophilic part and polyoxyethylene chain as the hydrophilic part. Due to the presence of sterols of natural origin, the surfactants are biocompatible, mild to skin and possess low toxicity (1). In fact, these surfactants are used as emulsifiers, and are available commercially. The bulky and nonflexible sterol groups are also expected to affect the selfaggregation and phase behavior of these surfactants in 7 JOS
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