Due to this special physical and chemical structure, ordinary silica particles are prone to problems such as a large number of adsorbed water molecules on the surface, secondary aggregation between molecules, and excessive specific surface area when forming aggregates, which affects the effect of their industrial applications. Specifically:

(1) The surface is hydrophilic
Because the surface of silica aggregate contains a large number of polar hydroxyl groups, it will have a strong adsorption effect on external water molecules, so that a large number of water molecules are adsorbed on the surface. During the processing of rubber products, a large amount of water molecules adsorbed on the surface of silica particles will cause bubbles and voids in the mixed colloid during vulcanization, thereby affecting the performance of the colloid. At the same time, the surface of rubber products is generally not polar, while the surface of silica contains a large number of polar hydroxyl groups, resulting in poor compatibility between the two, thereby affecting the reinforcing effect of silica.

(2) Poor dispersion
The structure of silica is a chain-like aggregate, and the ordinary silica produced by the precipitation method is prone to secondary aggregation and the structure is not easily destroyed when the aggregate is formed. Compared with the silica particles prepared by the gas phase method, the ordinary silica particles produced by the precipitation method are often cross-linked into a whole during aggregation, resulting in poor dispersibility of the silica particles. When used as an industrial reinforcing agent, the poor dispersibility is not conducive to the combination of silica and the reinforcing matrix, which will reduce its reinforcing effect.

(3) The specific surface area is too large
The silica particles have a smaller particle size and a larger specific surface area. Although a larger specific surface area usually promotes the process of rubber reinforcement, an excessively large specific surface area will enhance the cohesion between the silica particles, resulting in their presence in the rubber matrix. It is not easy to disperse, and it is easy to absorb a large amount of accelerators, delay vulcanization time, generate excessive heat, and burn the matrix during the processing of rubber products.

Therefore, most of silica needs to be modified before industrial application to improve its industrial application performance.