Do you know the types and properties of silicon dioxide?

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2022-02-19

Types and Properties of Silicon Dioxide

The reinforcing fillers used in silicone rubber are primarily synthetic silica, also known as precipitated silica. Precipitated silica is classified into gas-phase silica and precipitated silica.

a. Fumed silica

The size, specific surface area, surface properties, and structure of silica particles are influenced by factors such as the ratio of precursor gases, the combustion rate, and the residence time of the SiO2 nuclei in the combustion chamber.

The finer the particles of gas-phase fumed silica, the larger its specific surface area, and the better its reinforcing effect; however, its processability deteriorates. Conversely, coarser particles with a smaller specific surface area yield poorer reinforcement but improved processability.

Fumed silica is one of the most commonly used reinforcing agents for silicone rubber; compounds reinforced with it exhibit high mechanical strength and excellent electrical properties. Fumed silica can also be blended with other reinforcing fillers or weakly reinforcing agents to produce elastomers tailored to specific application requirements.

b. Precipitated silica

The properties of precipitated silica are influenced by precipitation conditions such as acidity and temperature.

Compared with silicone rubber compounds reinforced with fumed silica, those reinforced with precipitated silica exhibit slightly lower mechanical strength and poorer dielectric properties—particularly after exposure to moisture—while offering superior resistance to thermal aging. Moreover, the cost of the compounded rubber is considerably lower. When the mechanical strength requirements for the final product are not stringent, precipitated silica may be used alone or in combination with fumed silica.

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Precipitated silica is a high-tech inorganic fine chemical product.

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What method is used for the high-temperature surface treatment of precipitated silica?

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Precipitated silica is a high-tech inorganic fine chemical product.

White carbon black, also known as silica, is scientifically termed precipitated hydrated silica. It is a high‑tech inorganic fine chemical product whose main constituent is SiO₂. Its physical properties resemble those of carbon black, appearing as a highly dispersed white amorphous powder or flocculent powder; it is also processed into granular forms for commercial use. Lightweight, with an original particle size below 0.3 μm and a relative density ranging from 2.319 to 2.653, it has a melting point of 1750°C. It is insoluble in water and most acids, but absorbs moisture from the air, forming hygroscopic fine particles. It is soluble in caustic soda and hydrofluoric acid, while remaining inert to other chemicals; it does not decompose at high temperatures nor does it burn. It is chemically inert toward substrates, active ingredients, and additives, and exhibits excellent compatibility with many active components commonly used in vitamins, hormones, fluorides, antibiotics, enzyme preparations, and cosmetics. It possesses high electrical insulation properties. Owing to its porosity and large specific surface area, it demonstrates strong dispersibility in raw rubber and imparts superior reinforcing performance in rubber compounds. Surface‑modified hydrophobic silica readily disperses in oils, rubbers, and plastics as a reinforcing filler, significantly enhancing mechanical strength and tear resistance. Due to variations in manufacturing processes, the physical and chemical characteristics, as well as the microstructure, of silica may differ, leading to distinct application areas and performance outcomes.

2022-02-19

Do you know the types and properties of silicon dioxide?

The reinforcing fillers used in silicone rubber are primarily synthetic silica, also known as precipitated silica. Precipitated silica is classified into fumed silica and precipitated silica.

2022-02-19

What method is used for the high-temperature surface treatment of precipitated silica?

Surface high‑temperature treatment involves subjecting precipitated silica to elevated temperatures to remove adsorbed molecules—such as water and other low‑molecular‑weight species—from its surface. While this approach can modestly improve certain vulcanization properties, the effect is not particularly pronounced. Surface chemical treatment, on the other hand, entails reacting the active silanol groups on the silica surface with specific chemical reagents, thereby enhancing the compatibility and reactive activity of the silica with polymeric matrices. A wide variety of reagents can be employed for such chemical modification, and numerous methods exist; a substantial body of literature and patents addresses these approaches. The following provides a brief overview of some key aspects.

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