Fumed silica has significant light scattering ability due to its small particle size and network structure. Therefore, fumed silica has good optical properties in varnishes and is the first choice for high-grade paint matting agents.
The main characteristic parameters affecting the fumed silica matting agent are pore volume (porosity), average particle size and particle size distribution, surface treatment and the like. For a given fumed silica matting agent, its extinction efficiency increases with increasing pore volume. The average particle size of the fumed silica and its particle size distribution play an important role in the reduction of the gloss of the coating. For a given coating and film thickness, the matting effect is best when the matting agent particle size corresponds to the dry film thickness of the coating. The narrower the frequency band of the particle size distribution, the higher the extinction efficiency.