Hydrophobic Fumed Silica | Hydrophobic Nano Silica for Silicone Rubber,
Conductive Ink, RTV Sealant
Meta Description
Hydrophobic fumed silica is organosilane modified amorphous nano silica. It delivers stable thixotropy, thickening and reinforcement performance for silicone rubber, RTV adhesive, conductive ink, solvent-based coating and sealant. It features low water absorption and great anti-settling ability.
Hydrophobic Fumed Silica
Pain Points
- Silicone rubber and RTV adhesive have low viscosity, easy to sag on vertical surfaces
- Solid pigments, carbon powder and graphene powder settle quickly in ink and slurry, unstable during storage
- Unmodified silica absorbs moisture easily, introducing bubbles and weakening insulation performance of silicone products
- Poor tear strength and low hardness of finished silicone parts
- Fumed silica agglomerates badly and is difficult to disperse in non-polar silicone systems
- Viscosity fluctuates greatly under high humidity workshop environment
Solutions
Our hydrophobic fumed silica is manufactured via flame hydrolysis and subsequent organosilane surface treatment. The surface silanol groups are capped with organic groups to achieve water repellency. It provides reliable thixotropy and thickening effect, prevents sagging and sedimentation, enhances mechanical strength and insulation property. It performs consistently in non-polar systems including silicone polymer, silicone oil, solvent ink and solvent-based adhesive.
Product Definition
Hydrophobic fumed silica is amorphous nano silicon dioxide produced by flame hydrolysis of silicon tetrachloride, followed by organosilane surface modification. Partial surface silanol groups are replaced with organic functional groups, making it non-wettable with water. It serves as a high-performance thixotropic, thickening and reinforcing additive widely applied in silicone, ink and adhesive industries.
Features & Advantages
✅ Excellent thixotropy & thickening performance, effectively prevent sagging on vertical surfaces
✅ Low water absorption, moisture resistant, no bubbling for silicone & sealant products
✅ Great reinforcement effect, improve tear strength and hardness of silicone rubber
✅ Good dispersibility in non-polar & weak-polar systems (silicone oil, solvent ink)
✅ Fine nano particle size, less impact on product transparency
✅ Stable viscosity under different humidity conditions
✅ High chemical inertness, good compatibility with silicone polymer, solvent-based resin
✅ Anti-settling, keep carbon powder, graphene and metal powder suspended uniformly in conductive ink
Physical & Chemical Properties
| Item | Standard Value |
|---|---|
| Model | R972 |
| Specific Surface Area | 110 ± 20 m²/g |
| SiO₂ Content | ≥99.8% |
| Loss on Drying | ≤0.5% |
| pH Value (4% dispersion) | 4.0 - 6.0 |
| Tamped Density | 50 - 80 g/L |
| Carbon Content | 0.6 - 1.2 % |
Recommended Addition Ratio (based on total formula weight)
- Silicone rubber / RTV silicone sealant: 0.8% - 3.0%
- Solvent-based conductive ink, carbon paste, graphene ink: 1.0% - 2.5%
- Solvent-based coating: 0.5% - 1.8%
- Silicone oil compound: 0.4% - 2.0%
- Solvent-based adhesive: 0.6% - 2.0%
Instructions for Use
- High-shear dispersion equipment is required; simple low-speed stirring cannot achieve good dispersion.
- Add hydrophobic fumed silica slowly into polymer or solvent under high-speed dispersion machine, speed range: 2500 - 6000 rpm.
- Disperse continuously for 6 - 15 minutes until no visible agglomerates.
- Suggest adding in the early grinding and dispersion stage.
- Do not mix with large amount of other fillers at one time to avoid re-agglomeration.
- Avoid contact with water during processing.
Packaging
- 10kg / multi-layer kraft paper bag with inner PE liner
- 15kg / multi-layer kraft paper bag with inner PE liner
- Customized packaging is available upon customer request
Storage Method
Store in a dry, cool and well-ventilated warehouse. Keep packages tightly sealed. Keep away from moisture, high temperature and direct sunlight. Separate from water and volatile polar solvents.
Shelf Life
12 months under proper storage conditions. Once the package is opened, finish consumption as soon as possible and re-seal tightly after use.
- Hi, Winstar Silicone company, we are interested in your product silicone color masterbatch, could you please offer some free samples to us？ Our company address: ***LA,USA
- Hello Winstar, our product is compression molding product,could you advise which peroxide curing agent to use ?
- Hi friend, we have some problem in silicone to PVC bonding, that bonding strength is not well at all, how to improve it please ?
