1. Mixing and dispersing of rubber compound
     Since silica has a large specific surface area, it tends to be secondary aggregated, and it is easy to absorb water in the air, so that a strong hydrogen bond association is easily generated between the hydroxyl groups, thereby further improving the cohesive force between the particles, so the silica The mixing and dispersion are much more difficult than carbon black, and when a large amount of compounding is carried out, it is easy to form a gel, which hardens the rubber and generates heat during mixing. In order to achieve good dispersion, it is required to maintain the highest possible shear force during the initial mixing so that the aggregate particles of the silica are destroyed as much as possible without excessive mechanical degradation of the rubber molecular chain. . To this end, silica should be added in small portions to reduce heat generation. Properly increasing the mixing temperature is beneficial to remove some of the white carbon black surface to adsorb moisture, reduce the cohesive force between the particles, and contribute to the dispersion of white carbon in the rubber.

2. Structural Control in Silica Black Reinforced Silicone Rubber Mixture
Silica, especially fumed silica, is the best reinforcing agent for silicone rubber, but has a problem of hardening the rubber compound, commonly referred to as the "structural effect." Its structuring increases with the lengthening time of the rubber compounding, and even becomes so serious that it cannot be refining or scrapped. There are two explanations for this. One is that the silicone rubber end group condenses with the surface hydroxyl group of the silica; on the other hand, the silicone rubber silicon oxygen chain link forms a hydrogen bond with the hydroxyl group on the surface of the silica.
There are two ways to prevent structuring. One is to add some substances that can react with the hydroxyl groups on the surface of silica, such as hydroxy silicone oil, diphenyl silicon diol, silazane, etc. during mixing. When diphenylsilyl glycol is used, it should be treated at 160~200 °C for 0.5~1h after mixing. This prevents the structure of the silica filled silicone rubber. Another way is to modify the surface of the silica in advance, first remove some of the surface hydroxyl groups, and fundamentally eliminate the structuring.