HIFULL® HB-139 is hydrophobic fumed silica which is produced by hydrophilic fumed silica with a specific surface area of 200m2/g after chemical post-treatment with PDMS / Polydimethylsiloxane, also known as silicone oil.
Compared to untreated hydrophilic fumed silica, HB-139 loses its surface hydroxyl groups due to chemical reactions or shielding, making it hydrophobic. Its particle size increases, and the nitrogen adsorption-specific surface area decreases from 200m2/g to around 110±30 m2/g. Its pH ranges from 4.0% to 7.0% in a 4% dispersion of isopropanol-water solution (1:1 volume ratio). The pH change of hydrophobic fumed silica is influenced by the treating agent.
|Properties||Unit||Typical Value||Testing Standard|
|Specific surface area(BET)||m2/g||110±30||GB/T 20020|
|pH value in 4% dispersion||—||4.0～7.0||GB/T 20020|
|Loss on drying(2 hours at 105℃)||%||≤0.7||GB/T 20020|
|Loss on ignition(2 hours at 1000℃, based on material dried for 2 hours at 105℃)||%||≤10.0||GB/T 20020|
|Silica Content(Based on ignited material)||%||≥99.8||GB/T 20020|
|Tamped Density（Based on material dried at 105℃ for 2 hours）||g/L||40～60||GB/T 20020|
|Carbon Content (Based on material dried at 105℃ for 2 hours)||%||4.0～7.0||GB/T 20020|
“Structuring” refers to the phenomenon when rubber compound becomes hard during storage, its plasticity decreases, resulting in lose of properties to be reprocessed or used. PDMS-treated hydrophobic fumed silica enhances the reinforcement performance of silicone rubber without structuring even at high filler concentrations. It is particularly suitable for transparent systems, offering product transparency while providing high hydrophobicity. It exhibits exceptional anti-caking and flow-enhancing characteristics in powder coatings.
Uses and Applications
Due to its unique properties, PDMS or silicone oil-treated hydrophobic fumed silica finds wide applications in various fields such as:
Thickening and Thixotropic Behavior: The addition of PDMS-treated silica significantly increases the viscosity and thixotropic behavior of formulations. This ensures that the product maintains its thickness during storage and application, yet becomes less viscous when subjected to shear forces, allowing for smooth and effortless spreading.
Anti-Sagging Properties: PDMS-treated silica imparts anti-sagging properties to formulations, preventing the settling or sagging of heavier components. This is particularly important in products with suspensions or high-density ingredients, as it maintains the uniform distribution of particles and prevents undesirable separation.
Stability: With PDMS treatment, silica becomes an excellent stabilizing agent, contributing to the overall stability of formulations. It helps prevent phase separation, settling, or stratification of ingredients, ensuring the product retains its intended appearance, texture, and performance over time.
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