Silica (silicic acid)

Silica is characterised by chemical and physical properties that make it indispensable in many applications:

• High adsorption capacity: ideal for binding moisture or chemicals.

• Reinforcing effect: improves the mechanical properties of plastics and rubber.

• Temperature resistance: suitable for applications at high temperatures.

• Excellent dispersion: even distribution in various matrices.

• Chemical stability: does not react with many chemicals, except strong bases and hydrofluoric acid.

Silica is produced industrially by chemical processes that create highly pure and controlled products:

Precipitated silica

• Reaction: sodium silicate is treated with an acid (e.g. sulphuric acid).

• Precipitation: the silica precipitates out of the solution.

• Washing and drying: removal of impurities and water.

Fumed (pyrogenic) silica

• Flame hydrolysis: silicon tetrachloride is oxidised in a flame.

• Formation of silicon dioxide: extremely fine amorphous silicon dioxide is formed.

• Cooling and packaging: the product is collected and packaged.

Silica is used in numerous industries and products:

Rubber and plastics industry

• Filler: improves mechanical properties such as strength and abrasion resistance.

• Reinforcement: reinforcement of elastomers such as silicone or rubber.

Food and pharmaceutical industries

• Flow aid: prevents powders from clumping.

• Carrier: used in tablets and food supplements.

Paint and coatings industry

• Matting: reduces the gloss of paints and coatings.

• Rheology control: regulates the flow properties of coatings.

Technical applications

• Insulating material: high-temperature insulation for electrical appliances and construction.

• Catalysts: used as a carrier material in chemical processes.

Using silica offers numerous advantages:

• Versatility: can be used in numerous industries and applications.

• Cost efficiency: low-cost filler and reinforcing agent.

• Environmental friendliness: chemically stable and often recyclable.

• Increased performance: improved mechanical and optical properties of products.

Despite its advantages, there are also challenges in using silica:

• Dust formation: fine powder can cause handling problems.

• Processing: homogeneous dispersion can be difficult in some matrices.

• Reactivity: changes can occur in alkaline environments or at high humidity.

The two main types of silica differ in their production and properties:

Property	Precipitated silica	Fumed silica
Particle size	Coarser	Very fine
Purity	Medium to high	Very high
Applications	Filler, flow aid	Catalyst carrier, high-performance applications
Costs	Lower	Higher

• Is silica harmful to health? In its pure form, silica is harmless, but inhaled dust can irritate the respiratory tract.

• Can silica be recycled? Yes, silica can be reused, particularly in industrial processes.

• Is silica used in food? Yes, it is used as a flow aid (E551) in powders.

• What role does silica play in the rubber industry? It improves the mechanical properties of rubber compounds and increases abrasion resistance.

Silica is an essential ingredient in numerous industries, from rubber and plastics processing to the food and pharmaceutical industries. Its versatility, cost efficiency and the improved material properties it delivers make it an indispensable material in modern production. By selecting the right type, whether precipitated or fumed silica, specific requirements can be met optimally.