Chapter 13. Polymer Colloids for Cosmetics and Personal Care

Standardizing the White Cast Potential of Sunscreens with Metal Oxide Ultraviolet Filters

“…28 Pre-prepared ZnO and TiO 2 dispersions act as suspensions of metal oxide particles to inhibit the formation of larger aggregates and agglomerations that are typically produced in free-flowing powders. 29,30 The vehicles for dispersing ZnO and TiO 2 nanoparticles are integral to preventing high aggregation and agglomeration of the particles, while maintaining a broad-spectrum SPF. Utilizing pre-dispersed ZnO and TiO 2 in a sunscreen formulation enables more controlled particle distributions of ZnO and TiO 2 to be implemented into a formula, in comparison to freeflowing powders.…”

“…29 Utilizing polymeric dispersions, particle-particle attractions arising from metal oxide surfaces can be further mitigated in sunscreens through electrostatic stabilization, steric stabilization, or electrostatic stabilization approaches. 29,30 Polymeric dispersions of metal oxides give rise to colloidally stable conditions that overcome unwanted interparticle interactions that result in white cast. For example, polymer-induced stabilization can create an adsorption-induced adlayer on the metal oxide crystalline particles' surfaces, which results in controlled particle repulsion throughout the dispersion.…”

“…For example, polymer-induced stabilization can create an adsorption-induced adlayer on the metal oxide crystalline particles’ surfaces, which results in controlled particle repulsion throughout the dispersion. Steric stabilization utilizes an adlayer on the metal oxides’ surfaces, which offers stronger interparticle adsorption in comparison to polymer-induced stabilization. − Future developments in sunscreen formulation should include efforts to deagglomerate metal oxide particles sufficiently to retain the performance of UV absorption exhibited by non-dispersed particles, while remaining cosmetically elegant in formulations. Recent work compares polyoxyethylene (POE)-modified silicones of various branch-types as dispersants to examine the relationship between viscosity, UV absorption, and the sizes of ZnO and TiO 2 agglomerates …”

“…30−32 Pre-dispersions of ZnO and TiO 2 utilize hydrophobic solvents, such as poly(hydroxystearic acid) and polyricinoleate, as these are natural polymeric latexes that lead to film formation, and more effectively disperse pigments. 29 Utilizing polymeric dispersions, particle-particle attractions arising from metal oxide surfaces can be further mitigated in sunscreens through electrostatic stabilization, steric stabilization, or electrostatic stabilization approaches. 29,30 Polymeric dispersions of metal oxides give rise to colloidally stable conditions that overcome unwanted interparticle interactions that result in white cast.…”

“…The incompatibility between increased UV absorption from aggregated particles and the resulting white cast is often addressed by dispersing the particles into polar “carriers” in sunscreen formulations . Pre-prepared ZnO and TiO 2 dispersions act as suspensions of metal oxide particles to inhibit the formation of larger aggregates and agglomerations that are typically produced in free-flowing powders. , The vehicles for dispersing ZnO and TiO 2 nanoparticles are integral to preventing high aggregation and agglomeration of the particles, while maintaining a broad-spectrum SPF. Utilizing pre-dispersed ZnO and TiO 2 in a sunscreen formulation enables more controlled particle distributions of ZnO and TiO 2 to be implemented into a formula, in comparison to free-flowing powders. − Pre-dispersions of ZnO and TiO 2 utilize hydrophobic solvents, such as poly­(hydroxystearic acid) and polyricinoleate, as these are natural polymeric latexes that lead to film formation, and more effectively disperse pigments .…”