Application of Rheological Analysis for Dispersion System of Fine Particles

Abstract

The relationships between suspension rheology and its effect of UV-protection for various suspensions were analyzed, such as particle type, particle size, particle surface properties, and type of dispersants. The objective of this study is to achieve the effective UV-protective method by use of the accurate control of suspension rheology. The rheological properties are studied for suspension of ultra-fine TiO2 dispersed in silicone oil containing polyoxyethylene(POE) -modified silicones as dispersants. The effects of dispersion stability are evaluated through rheological methods and the flocculation mechanisms are discussed as a function of the molecular structures and HLB (Hydrophilic-lipophilic balance) of POE-modified silicones. The UV-protecting ability of suspensions of ultra-fine TiO2 particles is also discussed in relation to degree of flocculation. Furthermore, the study of rheological behavior is used complex suspensions of TiO2 and ZnO. The role of dispersants in heterogeneous flocculation behavior will be discussed in relation to their molecular structures to determine the optimum formulation of sunscreen cosmetics with high UV-protecting ability in both UVA and UVB regions. In the various cosmetics fields, the technology which formulates oil-in-water type emulsion containing fine particles in inner oil phase is the most general of them all. That can give the high UV-protection performance, smooth texture like non-powder, and natural color on the skin. The development and the application for this technology are additionally expected in cosmetic industries. © 2013, The Society of Rheology, Japan. All rights reserved.