AEROSIL 200 HV Fumed Silica - Thickener for Silicone and Casting Resins

Premium Hydrophilic Fumed Silica Thickener for Professional Silicone and Resin Applications

Vulstof Fumed Silica (AEROSIL® 200 HV by Evonik) is a hydrophilic, fumed silicon dioxide (SiO₂ > 99.8%) used to thicken and add thixotropy to liquid materials such as silicone, polyester, epoxy and polyurethane. The white powder with a specific surface area of approximately 200 m²/g dissolves colourless/transparent when mixed well, raises the viscosity to a spreadable or non-sag result and also increases the hardness (Shore value) of silicone. Only a little is needed: for silicone, 1% by weight is often enough for a spreadable result.

Key Benefits

• Versatile: → thickens silicone, polyester, epoxy and polyurethane.
• Dissolves transparent: → white powder that becomes transparent after good mixing, without affecting the colour.
• Food-safe in Siliconen Culinair®: → remains food-safe, unlike Thixo A/C.
• Suitable for addition and condensation: → usable in both silicone types, unlike Thixo A/C.
• Increases hardness: → increases the Shore value of silicone as well as the viscosity.
• Unlimited shelf life: → practically unlimited use when stored dry.

Typical Applications

• Thickening silicone (addition and condensation), including food-safe silicone.
• Thixotropy and anti-settling agent in polyester, epoxy and polyurethane resins.
• Paints, coatings, adhesives and sealants as a rheology control agent.
• Reinforcement of HTV and RTV-2 silicone rubber.
• Anti-caking and free-flow agent in powders.

Processing

1. Add the powder gradually to the liquid and mix thoroughly; the viscosity rises during and shortly after mixing.
2. Start low and determine the dosage experimentally: start at 0.5% by weight and increase in steps of 0.5%.
3. For silicone, approximately 1% by weight is often enough for a spreadable result.

Dosage for polyurethane (by weight of the total resin or component A, the polyol):

• 0.7-1%: slightly thickened, non-slump – still easy to pour but stays in place.
• 2-3%: gel-like, ideal for most trowel applications.
• 3-5% (up to 7%): thicker paste (petroleum jelly or peanut butter consistency) for vertical fills or fillets.

Technical Data

• Chemical name: silicon dioxide (fumed), SiO₂
• CAS number: 112945-52-5 / 7631-86-9
• Specific surface area (BET): 175-225 m²/g (nominal 200 m²/g)
• Tamped density: approx. 50 g/l
• pH value (4% dispersion): 3.7-4.5
• SiO₂ content: > 99.8%
• Loss on drying (2 hours at 105°C): ≤ 1.5%
• Colour: white powder (dissolves transparent)
• Shelf life: unlimited when stored dry

Special Notes

Although the powder is white, it is transparent in the dissolved state after good mixing. Unlike Thixo A or Thixo C, Fumed Silica can be used in both condensation and addition silicone, and the result in a food-safe silicone remains food-safe. Fumed Silica also increases the hardness (Shore value) of silicone; with Thixo this occurs to a lesser extent.

Safety

AEROSIL® 200 HV is not classified as hazardous under the CLP Regulation and does not require GHS labelling. Dust may be generated when handling the powder; avoid inhaling dust, ensure adequate ventilation and preferably wear a dust mask and safety goggles. For full information, please refer to the safety data sheet.

This product is AEROSIL® 200 HV by Evonik Operations GmbH, a world leader in the development and production of fumed silica for industrial and technical applications.

Professional Support

Do you have questions about the correct dosage for your resin or silicone, or about thickening food-safe silicone? Our specialists are happy to assist you. Contact us for personal advice.

Documentation

Product data sheet – Vulstof Fumed Silica