1. Mixing and dispersing of rubber compound
     Since white carbon black 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 white carbon black 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 white carbon black; on the other hand, the silicone rubber silicon oxygen chain link forms a hydrogen bond with the surface hydroxyl group of the white carbon black.
       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.
3. Mooney viscosity of rubber compound
      The ability of silica to form a gel is comparable to that of carbon black. Therefore, when the white carbon black is mixed, the Mooney viscosity of the rubber is increased, so that the processing property is deteriorated, so in the formulation containing silica. The choice and amount of softener is important. Paraffin hydrocarbons, naphthenes and aromatic hydrocarbons are often added to the IIR. The amount varies depending on the amount of silica and the Mooney viscosity, and is generally 15-30%. In NR, the softening effect of plant softeners such as rosin oil and tall oil is the best, the effect of synthetic softener is not great, and the softening effect of mineral oil is the lowest.
4. Vulcanization rate of rubber compound
        The surface of the white carbon black particles has a large number of micropores, and has a strong adsorption effect on the vulcanization accelerator, so that the vulcanization is obviously delayed. In order to avoid this phenomenon, on the one hand, the amount of the promoter can be appropriately increased; on the other hand, the active agent can be used to preferentially adsorb the active agent on the surface of the silica, thus reducing its adsorption to the promoter.
       The active agent is generally a nitrogen- or oxygen-containing amine, an alcohol, or an alcohol amine low molecular compound. Amines are more suitable for NR, such as diethanolamine, triethanolamine, butanediamine, hexamethylenetetramine, and the like. For SBR, alcohols are more suitable, such as hexanetriol, diethylene glycol, glycerol, polyethylene glycol, and the like. The amount of active agent should be determined according to the amount of white carbon black, the pH value and the rubber type. The general dosage is 1 to 3% of white carbon black.