Silica, a common chemical material, is believed to be familiar to everyone. It mainly refers to silica powder obtained by chemical means. Although the name is very similar to carbon black, it is not the same thing at all. It is named because of its reinforcing properties in rubber close to that of carbon black and its white appearance.

Silica powder
Silica itself has excellent properties such as light weight, good chemical stability, and good electrical insulation. However, because silica is ultra-fine and active silica particles, there are a large number of hydroxyl groups on the surface, which are hydrophilic and oleophobic. It is easy to absorb water and agglomerate, so it is often necessary to modify its surface hydrophobicity to improve its compatibility and binding force with the organic phase, improve its processing performance, and expand its application fields.

For example, silica is an important additive for superfine ammonium phosphate dry powder fire extinguishing agents. Because the ultrafine ammonium phosphate dry powder fire extinguishing agent has the characteristics of small particle size, large specific surface area, high surface activity, fast fire extinguishing speed, less dosage, and the fire extinguishing efficiency can be several times that of ordinary ammonium phosphate dry powder fire extinguishing agent, it has been increasingly valued by the industry. And development. However, since ammonium phosphate is very easy to absorb moisture and agglomerate in ultrafine conditions, it has higher requirements for dry powder formulation and surface hydrophobic treatment, especially the hydrophobic isolation additive white carbon black in the formula, which not only has small particle size but also hydrophobicity. Performance is also good.

In addition, hydrophobic silica also has a wide range of applications in the feed industry, fertilizer industry, chemical industry, microelectronics industry, aerospace industry, defense industry, large-scale integrated circuits, fiber optic cables and other fields, such as polar liquid thickening (such as epoxy resins); reinforcement of silicone elastomers (such as molded products); improving the dielectric properties of composites (such as cable composites); improving the scratch resistance of coatings and plastics, etc. It can be seen from the microscopic image of the rubber cross-section in the figure below that after adding the coupling agent, the distribution of silica in the rubber material is significantly more uniform, and the combination with the rubber material is more compact.

In order to obtain hydrophobic silica, it can be prepared by chemical reaction of hydrophilic silica with reactive silanes such as chlorosilane or hexamethyldisilazane. At present, in order to solve some special technical problems in the industry, various types of hydrophobic silica have been developed - the production of hydrophobic fumed silica by treating modified hydrophilic grade fumed silica with silane or siloxane Silica, in the final product, the chemical treatment agent is chemically bonded to the original hydrophilic oxide. In addition to the above-mentioned advantages of hydrophilic products, hydrophobic fumed silica products are characterized by: low hygroscopicity, very good dispersibility, and rheological adjustment even for polar systems. Some products, which are structurally modified on the basis of hydrophobic treatment, can provide further help for customers to develop new products and improve the performance of products - for example, in liquid systems, hydrophobic fumed silica can achieve high additions, The viscosity of the system has little effect.