Compared with carbon black, silica has finer particles and a larger surface area, so the vulcanizate has higher tensile strength, tear strength and wear resistance. However, due to the strong surface polarity and hydrophilicity of silica, the compatibility with hydrocarbon rubber molecules is not as good as that of carbon black. If it is filled in a large amount in rubber, it not only reduces the reinforcing effect, but also the setting of the rubber compound. Stress, compression set, wear and processing properties are not as good as carbon black filled rubber.

In the late 1970s, it was found that the white carbon black modified by the silane coupling agent can not only reduce the Mooney viscosity of the rubber compound, improve the processing property, but also reduce the heat generation and rolling resistance and improve the wear resistance. The introduction of silane coupling agents has made the application of silica in rubber leaps and bounds.

In the early 1990s, Michelin created the concept of low rolling resistance by replacing the carbon black in the tread rubber with highly dispersible silica, making fuel saving a reality, and “green tires” were produced as white carbon black. The application has opened up new horizons.

1 Classification of white carbon black
1.1 Precipitation method white carbon black
Precipitation method white carbon black is also called hydrated silica, and the rubber industry mainly uses precipitation method white carbon black. Precipitated silica is used in NR and S R for the manufacture of tires, rubber shoes, hoses, tapes, heat-resistant gaskets, medical supplies and a variety of other colored or white rubber products.

1.2 fumed silica
Gas phase white carbon black is also called anhydrous silica. Vapor-based silica is relatively expensive and is therefore mainly used in silicone rubber. It can be used in the manufacture of V-belts, rubber rollers, hoses, cables, oil seals and foamed products.

2 Application of white carbon black in rubber products
2.1 Tires
White carbon black was originally used only in white tire side car tire decorative strips, and its use has gradually expanded and is now used in various tire parts. Such as tread rubber, BIIR gas tight layer compound, tire carcass and belt layer, tire sidewall rubber, chafer cloth for truck tires, etc.

2.2 hose and tape
In the production of hoses and tapes, a large amount of silica is added to improve the wear resistance. The silanol on the surface of the silica plays a role in improving the degree of wetting of the rubber and the fabric, which is beneficial to the diffusion and penetration of the rubber.

2.3 rubber shoes
As the main reinforcing filler, silica is widely used in the production of rubber shoes, especially in transparent and translucent sole rubber. In the outsole formula, white carbon black can replace carbon black 100%. Therefore, the footwear industry has been the largest user of silica in the rubber industry.

2.4 wire and cable
Silicone rubber has excellent properties such as aging resistance, high and low temperature resistance and electrical insulation properties, and is widely used in the production of wire and cable products. Due to its high price and excellent reinforcing properties for silicone rubber, fumed silica is generally used only for silicone rubber and certain special products.

2.5 daily necessities
The good reinforcing properties of silica and its unique advantages such as whiteness and transparency make it widely used in rubber products such as household appliances and stationery. Its nitrogen adsorption specific surface area can reach 269 ~ 320 m2 • g-1, added to the rubber compound, which can make the rubber compound have good tensile strength, ozone aging resistance and dye color retention performance.


3 Application and development of white carbon black
3.1 Application and development of foreign white carbon black
3.1.1 Application

Silica has been produced since 1948 and used as a filler in the rubber industry. By the 1980s, about 67% of the world's precipitated silica was used in the rubber industry, of which 45% for footwear and 16% for tires. 6% for other rubber products.
3.1.2 Problems

Although the application of white carbon black has developed rapidly in recent years, its development is also facing some problems. (1) The rubber added with silica is difficult to disperse evenly. (2) Electrostatic accumulation is likely to occur in the compound in which white carbon black is added. (3) The price of white carbon black is high.


3.1.3 Solutions
Major manufacturers are working on the development of processing aids that can improve the processing properties of silica. For example, long-term exploration and precision screening of fatty acid soap additives can reduce the storage hardening of silica and improve the extrusion properties of the rubber. . Adding an antistatic material to the compound or adding a dispersant to improve the conductivity of the compound can effectively reduce static electricity accumulation. In addition, major producers of white carbon black are working hard to develop new varieties of white carbon black that are more reinforcing and dispersible.

3.2 Application and development of white carbon black in China
China's white carbon black production process has been relatively backward, with a single product specification. In recent years, the situation has improved and the process technology has made breakthroughs. Despite this, there are still many problems in the production of white carbon black in China. For example, the products are still dominated by ordinary precipitation method, white carbon black, too many manufacturers, the scale is too small, there is still a big gap between the varieties and the quality of foreign products; The production of white carbon black is extremely low; the highly dispersible white carbon black variety suitable for "green tires" needs to be developed.

Therefore, China should actively develop, produce and use a series of high-dispersion white carbon black varieties, strive to improve the stability and purity of white carbon black product quality; strengthen the development of white carbon black application technology; and strive to implement the expansion of gas phase white carbon The planning of black production capacity, the development of new varieties of white carbon black according to market demand.

4 Conclusion
As people's environmental awareness increases, “green tires” and high-grade rubber products will become more and more popular. As a high-grade reinforcing filler, the application of white carbon black, especially high-dispersion silica, will surely follow. There is a long-term development. Therefore, China's white carbon black production enterprises should pay close attention to the development and production of new series of highly dispersible white carbon black products, and strive to improve the quality and stability of white carbon black products in order to occupy a broad market in this application field as soon as possible.