Introduction to Wacker HDK Fumed Silica Product Line

Wacker HDK® Fumed Silica Product Line

1. Product Overview

Wacker HDK® is a leading global product line of nano-scale fumed silica. It is manufactured via flame hydrolysis, where volatile chlorosilanes are hydrolyzed in high-temperature oxyhydrogen flame to produce nano silica powder with high purity, large specific surface area and three-dimensional network structure. Since Wacker scientists discovered that purified silicon tetrachloride can react with hydrogen flame to produce fumed silica in 1966, Wacker HDK® has been a leading product dominating the global fumed silica market.Wacker’s product lines cover four major series: hydrophilic, hydrophobic, pharmaceutical & food grade and pre-dispersions. They are widely used in high-end fields such as coatings, adhesives, silicone rubber, composite materials, pharmaceuticals, food and electronics, featuring core functions including rheology control, reinforcement and thickening, anti-settling, flow aiding & anti-caking, and interface modification. Our company mainly supplies hydrophilic and hydrophobic fumed silica, and can recommend suitable products according to customer requirements.

II. Production Principle and Structural Characteristics

1. Production Technology

1. Raw materials: Volatile chlorosilanes such as silicon tetrachloride and trichlorosilane
2. High-temperature flame hydrolysis: Reacts in oxyhydrogen flame above 1200℃ to form nano-sized primary particles
3. Agglomeration formation: Primary particles fuse into chain aggregates and form micron-sized agglomerates after cooling
4. Post-treatment: Hydrophilic products can be directly collected; hydrophobic products need silane modification to endow surface hydrophobic property

2. Core Characteristics of Wacker HDK®

• High Purity: SiO₂ content ≥99.8%, with low metallic impurities and residual chlorine.
• High Specific Surface Area: Products cover a BET range of 50–400 m²/g to meet diverse application demands.
• Three-dimensional Network Structure: Forms hydrogen bond networks in liquids to achieve thixotropy, thickening and anti-settling effects.
• Controllable Surface Properties: Hydrophobic types contain silanol groups while hydrophobic ones are modified with methyl/alkyl groups, compatible with various solvent systems.
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• III. Product Line Classification and Typical Grades

  (1) Hydrophilic HDK®

  Featuring an unmodified surface with abundant silanol groups, it is compatible with polar systems and mainly serves for rheology control, reinforcement, thickening and thixotropy.

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• (2) Hydrophobic HDK®

  Featuring a silane-modified surface, it is hydrophobic and moisture-proof, compatible with non-polar/weakly polar systems, and mainly provides reinforcement, thixotropy and hydrolysis resistance.

• IV. Core Functions & Applications

  1. Rheology RegulationAchieve shear thinning via hydrogen bond network, prevent sagging and sedimentation, suitable for coatings, inks and adhesives.
  2. Mechanical Performance ReinforcementNanoparticles bond with polymer chains to greatly improve strength, modulus and wear resistance, applied to silicone rubber, elastomers and composites.
  3. Free Flow PerformanceReduce van der Waals force among powders as spacer, realize flow aid, anti-caking and anti-sticking, widely used in medicine, food and powder coatings.
  4. Other FunctionsPossess insulation, heat insulation, matting, emulsion stabilization and interface modification, fit for electronics, leather and composite material industries.