Due to this special physical and chemical structure, common silica particles tend to have a large number of water molecules adsorbed on the surface, secondary aggregation between molecules, and excessive specific surface area when forming aggregates, which affect the effect of its industrial application. Specifically, the results are shown as follows:
(1) The surface is hydrophilic
Because the surface of silica aggregates contains a large number of polar hydroxyl groups, it will have a strong adsorption effect on the external water molecules, so that the surface of silica aggregates adsorbs a large number of water molecules. A large number of water molecules adsorbed on the surface of silica particles in the rubber processing process will cause bubbles and cavities in the rubber vulcanization, which will affect the properties of the rubber. At the same time, the surface of rubber products is generally not polar, and the surface of white carbon black contains a large number of polar hydroxyl groups, resulting in poor compatibility between the two, which affects the reinforcing effect of white carbon black.
(2) Poor dispersion
The structure of white carbon black is chain-dendritic aggregates. The common white carbon black produced by precipitation method is prone to secondary aggregation and its structure is not easy to be destroyed when aggregates are formed. Compared with the silica particles prepared by gas phase method, the silica particles produced by precipitation method are often crosslinked into a whole during aggregation, which leads to the poor dispersion of silica particles. When used as industrial reinforcing agent, poor dispersion is not conducive to the combination of silica and reinforcing matrix, and will reduce its reinforcing effect.
(3) Excessive specific surface area
The particle size of silica silica is small and the specific surface area is large. Although the larger specific surface area usually plays a promoting role in the reinforcement process of rubber, too large specific surface area will enhance the cohesion between silica particles and make it difficult to disperse in the rubber matrix. In the process of rubber products, it is easy to adsorb a large number of accelerator, delay the curing time, produce too much heat, scorch matrix and other problems.
Therefore, most of the white carbon black needs to be modified before industrial application to improve its industrial application performance.