White carbon black, especially gas-phase white carbon black, is the best reinforcing agent for silicone rubber, but there is a problem of hardening the mixed rubber, commonly known as the "structural effect". Its structure increases with the prolonged storage time of the rubber material, even to the extent that it cannot be recycled or scrapped. There are two explanations for this, one is that the end groups of silicone rubber are condensed with hydroxyl groups on the surface of silica; On the other hand, it is believed that the silicon oxygen chains of silicone rubber form hydrogen bonds with the surface hydroxyl groups of silica. There are two ways to prevent structuring. One is to add certain substances that can react with the hydroxyl groups on the surface of white carbon black during mixing, such as hydroxysilicone oil, diphenylsilanediol, silazane, etc. When using diphenylsilanediol, it should be treated at 160-200 ℃ for 0.5-1h after mixing. This can prevent the structured filling of silicone rubber with white carbon black. Another approach is to pre modify the surface of white carbon black by removing some surface hydroxyl groups, fundamentally eliminating the structure.



Mooney viscosity of rubber material
The ability of silica to generate gel is comparable to that of carbon black. Therefore, when mixing silica, the Mooney viscosity of the rubber compound is increased, which worsens the processing performance. Therefore, the selection and amount of softener in the rubber compound formula containing silica are very important. In IIR, paraffin hydrocarbons, cycloalkanes, and aromatic hydrocarbons are often added, and the amount used varies depending on the amount of white carbon black used and the Mooney viscosity, generally reaching 15-30%. In NR, plant-based softeners such as rosin oil and tall oil have the best softening effect, while synthetic softeners have little effect, while mineral oil has the lowest softening effect.

Vulcanization rate of rubber material
The surface of white carbon black particles has a large number of micropores, which have a strong adsorption effect on vulcanization accelerators, thus significantly delaying vulcanization. To avoid this phenomenon, on the one hand, the dosage of the accelerator can be appropriately increased; On the other hand, surfactants can be used to preferentially adsorb on the surface of white carbon black, thereby reducing its adsorption of accelerators.

Active agents are generally low molecular weight compounds of amines, alcohols, and alcohol amines containing nitrogen or oxygen. For NR, amines are more suitable, such as diethanolamine, triethanolamine, butylamine, hexamethylenetetramine, etc. For SBR, alcohols are more suitable, such as hexanol, diethylene glycol, glycerol, polyethylene glycol, etc. The amount of activator should be determined based on the amount of white carbon black, pH value, and rubber variety, with a general amount of 1-3 times that of white carbon black