Precipitated silica has excellent properties such as porosity, high dispersibility, light weight, good chemical stability, high temperature resistance, non combustion, and good electrical insulation, making it an important reinforcing filler. The most important application of silica is as a reinforcing agent for rubber, with a dosage of approximately 80% -90% of the total production. It can be widely used in many fields of the rubber industry.

1. Application of precipitated silica in rubber products


1.1 Tires
White carbon black was initially only used in decorative strips for white sidewall car tires, but its use gradually expanded. At present, white carbon black has been used in various tire components, including truck tires, sedan tires, agricultural tires, and so on. According to the material of the cord fabric, it is divided into all steel, semi steel, and fiber cord fabric tires, and the parts used include the tread, belt layer, sidewall, and steel wire adhesive. In traditional bias tires, silica can improve the tear resistance of the tread and the adhesion performance between rubber and cord. With the increasing requirements for radial tires, environmental protection, energy conservation, and comfort, the application of white carbon black in tires is becoming increasingly important. At present, the basic requirements for tires are:

(1) Having high grip on wet roads (anti slippery) or good traction to ensure the safety of vehicles and personnel. (2) Low rolling resistance to save fuel and reduce exhaust emissions. (3) Good wear resistance and long service life. In order to achieve the above performance, the application of white carbon black, especially highly dispersed white carbon black, in tread rubber is essential, especially the emergence of green tires, which has sparked the development heat of large precipitation method white carbon black manufacturers in the world for highly dispersed precipitation method white carbon black.

1.2 Silicone rubber

Silicone rubber has high heat resistance, excellent cold resistance, ozone resistance, atmospheric aging resistance, and excellent electrical insulation. In addition, silicone rubber has low water absorption and can be stored in damp places for a long time. It can be widely used in aerospace, military, electrical, medical and other departments. However, silicone rubber molecules have a spiral structure, high flexibility, weak intermolecular forces, and are difficult to crystallize. The tensile strength of raw rubber after vulcanization does not exceed 0.34MPa, which greatly limits its application. Adding reinforcing fillers is the main means of adjusting the physical and mechanical properties of silicone rubber, and only by adding reinforcing materials such as silicone rubber can it have practical value. In order to reduce the production cost of silicone rubber products, the market has started to partially replace gas-phase silica with ultrafine precipitation method silica, and significant breakthroughs have been made in application research. As a result, the demand for ultrafine precipitation method silica specifically for silicone rubber has rapidly increased. In response to this situation, major manufacturers of ultrafine precipitated silica in the world have invested in the development and establishment of ultrafine precipitated silica production lines for silicone rubber in recent years.

1.3 Rubber roller, tape, hose and other products and plastics


White carbon black is widely used in the preparation of light colored and high-performance products in printing rubber rollers, rice milling rubber rollers, textile rubber rollers, and papermaking rubber rollers. Steel woven rubber pipes, high-strength conveyor belts, colored rubber pipes, adhesive tapes, colored sealing products, and colored high-performance cable sheaths are all inseparable from white carbon black. After being ultra refined, white carbon black can be used as a blowing agent for plastic films and an additive for EVA plastic foaming materials. Compared with commonly used inert fillers such as calcium carbonate, white carbon black can significantly improve the wear resistance, tear strength, and hardness of materials, reduce compression permanent deformation and thermal shrinkage. After formula optimization design, performance can be improved and cost can be reduced.


1.4 Daily necessities

The excellent reinforcement performance of white carbon black and its unique advantages such as pure white and transparency have made it widely used in rubber products in household appliances, cultural and sports goods, and other fields of daily life. Especially in recent years, the reflectivity of nanoscale white carbon black developed in the ultraviolet wavelength range reaches about 90%, which is very beneficial for extending the color retention period of colored rubber products and improving color stability. Its nitrogen adsorption specific surface area can reach 269-320m2/g. Adding it to the rubber material can make the rubber material have good tensile strength, ozone aging resistance, and dye color retention performance.

2. Application and Development Trends of White Carbon Black


2.1 Application of White Carbon Black

White carbon black has been produced since 1948 and used as a filler in the rubber industry. By the 1980s, about 67% of precipitated white carbon black worldwide was used in the rubber industry, with 45% used in footwear, 16% used in tires, and 6% used in other rubber products. Since 1991, when French Michelin announced its vigorous research on "green tires," major tire companies in Europe, the United States, and Japan have successively accelerated their development pace. "Green tires" have become the mainstream of tire industry development in the 21st century, and white carbon black can be used in a high proportion or completely replace carbon black as a reinforcing agent to produce "green tires".


2.2 Development Trends of White Carbon Black

(1) Granulation of white carbon black for rubber: White carbon black is widely used as a reinforcing filler, but powdered white carbon black usually has a large specific surface area and low density, which causes severe flying during use, inconvenient transportation, and inaccurate measurement, affecting the quality of rubber products and the health of operators. Granulation (large or micro bead particles) of white carbon black has a significant effect on product quality control and the improvement of the operating environment. With the increase of the amount of silica used in rubber, the granulation of silica for rubber has become a theme of environmental protection in the rubber industry. Granulated silica has been industrialized and applied in foreign countries, while further development is needed in China.

(2) Refinement of white carbon black: Refinement refers to the precise control of the surface area, particle size, and surface characteristics of the finished product by controlling the proportion, flow rate, reaction pressure, temperature, and time of materials in the production process of white carbon black according to the requirements of different uses, and through post-treatment processes such as filtration, washing, and drying, to meet the application requirements of different users.

(3) High dispersion white carbon black: High dispersion white carbon black is a type of white carbon black product with high dispersibility and reinforcement, and no dust. It is necessary for improving the application performance of white carbon black in the future, increasing its usage in materials, especially in the production of "green tires". The current demand for "green tires" is increasing, and the demand from the tire industry has become the main growth point of white carbon black demand. Therefore, researching and producing more dispersed white carbon black products is an important task for Chinese white carbon black production enterprises.


(4) Surface treatment of white carbon black: Due to the presence of polysiloxane inside the white carbon black and active silanol groups on the outer surface, it is hydrophilic and difficult to wet and disperse in the organic phase. Moreover, due to the presence of hydroxyl groups on the surface, the surface energy is large, and the aggregates tend to aggregate, thus affecting the application performance of the product.

3. Conclusion

With the increasing awareness of environmental protection among people, high-end rubber products will receive more attention, and the application of white carbon black, especially highly dispersed white carbon black, as a high-end reinforcing filler, will inevitably have significant development. In Europe, the application of white carbon black in tires is approaching saturation, while this field in China has not yet been fully developed. Therefore, Chinese white carbon black production enterprises should quickly develop and produce new varieties of highly dispersed white carbon black; Strive to improve the quality and stability of white carbon black products; Strengthen the development of application technology for white carbon black, especially in tire tread compounds; Efforts will be made to implement the plan to expand the production capacity of precipitated silica.