Substances used as surface treatment agents are, in principle, substances that can interact with the hydroxyl groups on the surface of silica, and include the following.

1) Alcohols 2) Chlorosilanes 3) Alkoxysilanes 4) Hexamethyldisilazane 5) Silazane.

(2) The reinforcement mechanism of silica and the reinforcement mechanism of surface chemical silica to silicone rubber are considered to have the following two types.

a. The rubber is adsorbed by the filler particles. The filler particles adsorb the polymer, so that the rubber molecular segments are directly fixed in the vicinity of the filler particles or oriented along the surface of the filler or retained by the filler aggregates.

b. Rubber and Filler Particles Combination Filler particles combine with polymer segments to produce effective crosslinking and polymer entanglement of the filler particles.

Based on the above two functions, silica can play a reinforcing effect on silicone rubber.

Due to the different production methods of silica, its acidity and alkalinity are different. The fumed silica is acidic, and the precipitated silica is alkaline. The pH of the purest HCL-free fumed silica is 6, which is due to the dissociation of the hydroxyl groups on the surface of the silica to produce H+ in water. When the pH value is lower than 4.6, it is caused by the retained HCL caused by high temperature hydrolysis.