The Secrets of Silicon Dioxide

Silicon dioxide, including silicon dioxide for the rubber industry, feed additives, and other applications, is mainly used in the following areas.

(1) Silicon dioxide for the rubber industry: Silicon dioxide can significantly improve the physical properties of rubber materials and reduce the rolling resistance of tires without sacrificing their wet skid resistance. Adding silicon dioxide to tire tread rubber can improve the tread's cut and tear resistance. Compared with ordinary carbon black-filled rubber, the rolling resistance of silicon dioxide-filled rubber can be reduced by 30%. High-dispersion silicon dioxide is a type of silicon dioxide used in green tires, which can effectively reduce rolling resistance, save fuel consumption, improve wet skid resistance, enhance vehicle safety, reduce tire noise, and reduce noise pollution. Furthermore, it is closer to carbon black in terms of reinforcement and wear resistance, allowing it to replace carbon black to a greater extent, with a replacement ratio of 50-70% or even higher.

(2) Silicon dioxide feed additive: Precipitated silicon dioxide is mainly used as an adsorbent and to increase the flowability of feed in feed additives, particularly in the vitamin manufacturing industry. Adding precipitated silicon dioxide to vitamin products can adsorb vitamin nutrients and prevent caking, providing a sustained-release effect for the nutrients in the vitamins.

(3) Other applications of silicon dioxide: Used in medicine, oral care, mining, agricultural chemicals, papermaking, and other fields.

1. Classification by manufacturing method

Silicon dioxide, classified by manufacturing method, can be divided into precipitated silicon dioxide and fumed silicon dioxide. A comparison is as follows:

Precipitated silicon dioxide, also known as precipitated hydrated silicon dioxide, is commonly prepared using a neutralization precipitation reaction of silicate (mainly sodium silicate) and inorganic acid (usually sulfuric acid or hydrochloric acid). After precipitation, the hydrated silicon dioxide is filtered using a rotary drum filter press or plate and frame/box filter press to remove excess water and reaction byproducts, resulting in a silicon dioxide filter cake. This is then pulped and dried (usually by spray drying) to obtain the finished product. Further milling or granulation can produce products with a range of specifications. By controlling the material ratio, flow rate, temperature, and time of the reaction process, products with different specific surface areas, particle sizes, morphologies, structures, and porosities can be obtained. Precipitation methods can be further divided into acid precipitation methods, two-step methods using acidic silica sol, ammonolysis precipitation methods, and carbon dioxide methods.

Precipitated silicon dioxide has a significant price advantage and accounts for over 90% of the domestic market share. It is widely used in rubber, tires, footwear, rubber and plastic products, silicone rubber, coatings, cosmetics, toothpaste, and feed industries.

Fumed silicon dioxide, also known as pyrogenic silica, is produced using a thermal decomposition method, a dry method, or a combustion method. The preparation principle involves a high-temperature (above 100℃) hydrolysis reaction of silicon halide compounds in hydrogen and oxygen combustion water, followed by rapid cooling, and subsequent processing steps such as aggregation and deacidification to obtain the product.

The application areas of fumed silicon dioxide differ from those of precipitated silicon dioxide. Fumed silicon dioxide does not contain crystalline water, has a small particle size, a large specific surface area, and exhibits extremely strong stability, dispersibility, reinforcing properties, thickening properties, and thixotropy. Therefore, it is widely used in many industrial fields, including silicone rubber, toner, coatings, electronics, electricity, automobiles, construction, agriculture, medicine, and cosmetics. Because its molecular structure is similar to silicone rubber, it can be used as a light-colored reinforcing material for silicone rubber to enhance the tensile strength, improve the elastic modulus, and increase the elongation of silicone rubber products.