Do you know about the types and characteristics of silica?
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Author : TRUNNANO
Update time : 2023-03-28 15:11:18
Types and properties of silica
Do you know about the types and characteristics of silica? I believe that many people have a relatively small understanding of silica, today we will learn together some basic knowledge of silica, silica products are mainly divided into two categories: fumed silica and precipitation method silica, what are their characteristics? Specifically, we go down together to understand it.
What is Fumed silica?
The size, specific surface area, surface properties, and structure of fumed silica particles are related to the ratio of the raw gas, the combustion rate, and the residence time of the SiO2 nucleus in the combustion chamber.
The finer the fumed silica particles, the larger its specific surface area, and the better the reinforcement effect, but the worse the operating performance. On the contrary, its coarser particles, the specific surface area is also small, and the reinforcement effect is poor, but the operability is better.
Fumed silica is one of the most commonly used reinforcing agents for silicone rubber, and the rubber reinforced by it has high mechanical strength and good electrical properties of the vulcanized rubber. Fumed silica can also be used with other reinforcing agents or weak reinforcing agents to make different rubber materials with different requirements.
However, the price is the disadvantage of fumed silica, because of the high price of raw materials and the large amount of energy required for production, it has a greater disadvantage compared to precipitated silica in terms of price and environmental protection, but nowadays, with the improvement of the precipitated silica process, it is gradually able to partially or even completely replace fumed silica.
Fumed silica application areas
Fumed silica applications are different from those of precipitated silica. Fumed silica is a fine, special amorphous silica product produced by high-temperature hydrolysis of halothane over a hydroxide flame. Fumed silica does not contain crystalline water, has a small particle size and a large specific surface area, and has excellent stability, dispersibility, reinforcement, thickening and thixotropy, and the product purity can be as high as 99.8%. It is used as a reinforcing agent in the field of silicone rubber products and mainly used as a reinforcing agent and thickening agent in the field of coating and printing ink.
Precipitated silica is the most important type
Silicon dioxide is an inorganic substance with the chemical formula SiO2 and can be classified according to the manufacturing method into fumed silica and liquid silica. Further distinctions can be made between precipitated silica and gel silica based on the pH value of the reaction system and whether or not the reaction process is gelatinized.
What is Precipitated silica?
Precipitated silica products are divided into traditional precipitated silica, which is produced from sulfuric acid, hydrochloric acid, CO2 and water glass, and special precipitated silica, which is produced by special methods such as supergravity technology, sol-gel method, chemical crystal method, secondary crystallization method or inverse micellar microemulsion method.
The performance of precipitated silica is influenced by the precipitation conditions such as acidity and temperature.
Compared with the silicone rubber reinforced with fumed silica, the mechanical strength of the rubber reinforced with traditional precipitated silica is slightly lower, and the dielectric properties, especially after moisture, are poorer, but the heat aging resistance is better, and the cost of the compound is much lower. When the mechanical strength of the product is not high, precipitated silica is available or used with fumed silica.
Precipitated silica applications
Precipitated silica, known as precipitated hydrated silica or precipitated silica, is made by reacting a solution of water glass with an acid (usually sulfuric acid), precipitating, filtering, washing and drying. Because of its chemical inertness and stability to chemical agents and its ability to significantly improve the mechanical properties of rubber products (such as tensile strength, abrasion resistance, aging resistance, tear resistance, etc.), it is widely used as a chemical filler in the rubber industry, animal feed carrier, food, medicine, oral care, paper, coatings, agrochemicals, silicone rubber and many other fields.
In the pharmaceutical field, highly dispersible silica is used as a carrier for vitamin E. In the rubber field, it is mostly used as a replacement for carbon black and is called silica, while outside the rubber industry, it is mostly called silica.
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