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

1. Application of precipitated silica in rubber products
1.1 Tires
Silica was initially only used in white sidewall car tire decorative strips, and its use was gradually expanded. At present, silica has been used in various tire components, including truck tires, passenger car tires, agricultural tires, etc. According to the ply material, it is divided into all-steel, semi-steel and fiber ply tires. The parts used include tread, belt layer, sidewall and steel wire adhesive. In traditional bias tires, silica can improve the tear resistance of the tread and the adhesion between rubber and cord. With the increasingly high requirements of tire meridianization, environmental protection, energy saving and comfort, the application of silica in tires is becoming more and more important. At present, the basic requirements for tires are:

(1) It has higher grip on wet road (wet skid resistance) or better traction to ensure the safety of vehicles and personnel.
(2) Small rolling resistance to save fuel and reduce exhaust emissions.
(3) Good wear resistance and long service life. In order to obtain the above properties, the application of silica, especially high-dispersion silica, in tread rubber is essential, especially the advent of green tires has triggered the international large-scale precipitation silica manufacturers to highly disperse silica. The heat of development of precipitated silica.

1.2 Silicone rubber
Silicone rubber has high heat resistance and excellent cold resistance, ozone resistance, atmospheric aging resistance and excellent electrical insulation. In addition, silicone rubber has low water absorption, can be stored in humid places for a long time, and can be widely used in aviation. Aerospace, military, electrical, medical and other departments. However, silicone rubber molecules have a helical structure, high flexibility, weak intermolecular force, and it is 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 method to adjust the physical and mechanical properties of silicone rubber, and only adding reinforcing material silicone rubber has practical value. In order to reduce the production cost of silicone rubber products, the market began to partially replace fumed silica with ultra-fine precipitation silica, and great breakthroughs have been made in application research, so the demand for ultra-fine precipitation silica for silicone rubber is rapid. Increase. In response to this situation, in recent years, the world's major producers of ultrafine precipitation silica have invested in the development and establishment of ultrafine precipitation silica production lines for silicone rubber.

1.3 Cots, tapes, hoses and other products and plastics
Silica is widely used in the preparation of light-colored products and high-performance products in printing rubber rollers, rice milling rubber rollers, textile rubber rollers, and paper-making rubber rollers. Steel braided hoses, high-strength conveyor belts, colored hoses, tapes, colored sealing products, colored high-performance cable jackets and other products are all inseparable from silica. After being ultra-fine, silica can be used as a blown film release agent for plastic films and an additive for EVA plastic foam materials. Compared with the commonly used inert fillers such as calcium carbonate, silica can significantly improve the wear resistance, tear strength and hardness of the material, and reduce the compression set and thermal shrinkage. cost.

1.4 Daily necessities
Silica's good reinforcing properties and unique advantages such as pure white and transparency make it widely used in rubber products in household appliances, stationery and other life fields. In particular, the reflectivity of nano-scale silica developed in recent years in the ultraviolet wavelength range is about 90%, which is very beneficial to prolong the color retention period of colored rubber products and improve the stability of color and luster, and its nitrogen adsorption specific surface area can reach 269～320m2/g, when added to the rubber compound, it can make the rubber compound have good tensile and elongation properties, anti-ozone aging properties and color retention properties of dyes.

2. Application and development trend of silica 2.1 Application of silica
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% was used in footwear and 16% in tires. , 6% for other rubber products. Since 1991, when the French Michelin Company announced to vigorously carry out research on "green tires", major tire companies in Europe, the United States and Japan have accelerated the pace of research and development. "Green tire" has become the mainstream of tire industry development in the 21st century. Silica can be used in a high proportion or completely replace carbon black as a reinforcing agent to produce "green tire".

2.2 The development trend of silica
(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 a low density, which is seriously flying during use, inconvenient to transport, and inaccurate in measurement. , affecting the quality of rubber products and the health of operators, while granulated (large particles or microbead particles) silica has a significant improvement effect on product quality control and operating environment. With the increase in the amount of silica, the granulation of silica for rubber has become the theme of environmental protection in the rubber industry. The granulated silica has been industrialized and applied abroad, and China needs to be further developed.

(2) Refinement of white carbon black: Refinement refers to 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, after filtering, washing and drying. In order to achieve precise control of the surface area, particle size and surface characteristics of the finished product, it can meet the application requirements of different users.

(3) Highly dispersed silica: Highly dispersed silica is a kind of silica product with high dispersibility and reinforcement, and no dust. It is to improve the application performance of silica in the future and increase Medium dosage, especially the product necessary for the production of "green tires". At present, the demand for "green tires" is increasing, and the demand from the tire industry has become the main growth point of the demand for white carbon black. Therefore, the research and development and production of white carbon black products with better dispersion are China's white carbon black production enterprises. an important task.

(4) Silica surface treatment: Due to the polysiloxane inside the silica and the active silanol groups existing on the outer surface, it is hydrophilic, and it is difficult to wet and disperse in the organic phase. Moreover, due to the presence of hydroxyl groups on its surface , the surface energy is large, the aggregates tend to agglomerate, so the application performance of the product is affected.

3. Conclusion
With the enhancement of people's awareness of environmental protection, high-end rubber products will receive more attention, and the application of silica as a high-end reinforcing filler, especially high-dispersity silica, will surely develop by leaps and bounds. In Europe, the application of silica in tires is close to saturation, while this field in China has not been fully developed. Therefore, China's silica production enterprises should pay close attention to the development and production of new varieties of high-dispersion silica; strive to improve the quality and stability of silica products; strengthen the development of silica application technology, especially in tire tread compounds applications in; efforts to implement plans to expand the production capacity of precipitated silica.