How to Control Powder Alignment to Maximize Functionality and Performance of Color Cosmetics and Sunscreen

Abstract

IntroductionTitanium dioxide and iron oxides are used as functional powders in color cosmetics and sunscreen formulas, along with other compounds such as surfactants, emollients, and preservatives 1 . The development of functional powders that can form a uniform layer on the skin is critical to their functionality in cosmetics and sunscreens to attain two major benefits, i.e. esthetics and protection 2 . Our skin tends to be exposed to harmful environments, including various types of light, such as UV and blue light, and environmental stimuli such as allergens and pollutants. However, the preparation of color cosmetics and sunscreen formulas that can form a uniform applied layer on the skin is challenging 2 because they contain volatile solvents such as water, cyclopentasiloxane, and branched hydrocarbons. The evaporation of volatile liquids from their thin layers usually take place in a far-from-equilibrium condition in which Marangoni convection causes a spatial distribution of the content the content 3 9 , which critically influences

Factors to control the alignment of surface‐treated titanium dioxide powders to maximize performance of sunscreens

“…The predispersion (140 ml) thus prepared was mixed with 500 g of Zirconia beads having a diameter of 1 mm in the grinding pot of the bead mill (EASY NANO RMB, AIMEX CO., LTD), and grinding was continued for 45 min at 1405 rpm. The dispersion was then diluted with an identical volume of the liquid to make the final weight ratio of the powder to the liquid at 1.0:7.0 to adjust the viscosity approximately at 5.0 × 10 −2 Pa s. The stability of the dispersions has been verified in our previous study by SEM observation [13]. The rheological texture of each dispersion was thus almost identical to each other.…”

“…In our previous study, the surface pseudo‐HLB of the treated powders was found to be an important index for forming their uniform layer [13]. Seven types of surface‐treated powders, TS , DG , PM , TS / DG , DG / PM , TS / PM and TS / DG / PM samples, having pseudo‐HLB in the range of 3.5–8.5 were prepared in this study (Table 4).…”

“…Seven types of surface‐treated powders, TS , DG , PM , TS / DG , DG / PM , TS / PM and TS / DG / PM samples, having pseudo‐HLB in the range of 3.5–8.5 were prepared in this study (Table 4). The values of pseudo‐HLB were calculated according to our previous study [13]. To find the other factors that enhance the ability to form a powder layer possessing high UV shielding ability, the ratio of D5 and ID for the preparation of mixed solution was changed at first to observe the effects of surface tension of the liquids.…”

“…Our recent study showed that the surface pseudo‐HLB of the treated powders is an important index for forming their uniform layer. It was found that the alignment of powders tends to become uniform by preparing powders possessing the optimum pseudo‐HLB [13]. In this study, we focussed on how other factors affect the uniformity of powder alignment.…”