During the high temperature hydrolysis and condensation of fumed silica, some silicon hydroxy groups (Si-OH) remain on the surface, and the presence of surface silanol groups makes the surface of the fumed silica more polar and has higher surface activity. Figure 4 is a schematic view of the surface structure of fumed silica

Figure 4 Schematic diagram of the surface structure of fumed silica

It can be seen from the figure that there are "siloxy" and "silicon hydroxy" on the surface of fumed silica, wherein the silanol has high activity, can form hydrogen bonds, or react with other groups, which also ensures A stable network can be formed between the silica particles while having good interaction with other media, so that the silica exhibits good reinforcement, toughening, thickening thixotropic and anti-settling properties.

In addition, the presence of silanol also provides the possibility of surface modification of fumed silica. The surface modifiers of different structures are selected to react with the silanol groups, and some functional groups are grafted to the surface of the fumed silica, thereby The function of fumed silica is more diverse.