There are two major types of fumed silica: non-treated and treated, the former being hydrophilic and the latter hydrophobic.
★ The so-called non-treatment type fumed silica refers to: silica fine powder generated by the gas phase method, which is directly accumulated, purified, collected, compressed, and packed without being treated with other chemical agents, and hydroxyl groups remain on the surface of the silica particles. It is hydrophilic.
★ The so-called treated fumed silica refers to: non-treated fumed silica is treated with chemical reagents, and the surface hydroxyl group is replaced by the corresponding group (usually a hydrophobic group), so it is hydrophobic. This type of product is further divided into two sub-categories of fully processed and incompletely processed.
Hydrophobic silica cannot be wetted by water and cannot be dispersed in water. Although hydrophobic silicas are denser than water, they can float on water