Dow SILASTIC RTV-3481 Fast – Dry Condensation Mold Rubber for Concrete & Casting Resins

Premium Dry Condensation Silicone Rubber for Professional Concrete and Casting Resin Applications

The Dow SILASTIC RTV-3481 Fast is a two-component condensation-curing (RTV-2) mold rubber that cures at room temperature into a strong, dry silicone rubber. The set combines the RTV-3481 A component with the fast RTV-3081 F catalyst, mix ratio 100:5 by weight. With a Shore A hardness of 23, an off-white final color and a pot life of 30 to 45 minutes at 23 °C, the material is highly flowable and self-de-airing. Final mechanical properties are reached after 7 days. The rubber is ideally suited to the detailed reproduction of figures, ornaments and model-making, and to molds for casting concrete, plaster, wax, soap and casting resins such as polyurethane and polyester.

The RTV-3081 F is the fast catalyst; for a longer mold life with polyester casting resin, Dow offers the RTV-3081 R, available from us as Dow Silastic RTV 3481 R.

Key Benefits

• High tear strength – 24 kN/m: withstands repeated demolding of complex replicas without tearing.
• High elongation at break – 543%: high elasticity makes releasing undercuts and complex shapes easy.
• Low linear shrinkage – 0.2 to 0.4%: dimensionally accurate castings that retain fine detail.
• Good tensile strength – 4.6 MPa: durable rubber that survives long production runs.
• Fast cure – demolding time maximum 6 hours: short turnaround thanks to the fast RTV-3081 F catalyst.
• Highly flowable – 22,100 mPa·s mixture: self-de-airing and easy to pour around fine details.

Typical Applications

• Molds for concrete and concrete ornaments
• Molds for polyurethane and polyester casting resin
• Castings in plaster and porcelain plaster
• Wax and candle production
• Soap casting
• Reproduction of figures and sculptures
• Model-making and industrial prototypes

Processing Instructions

1. Stir the A component thoroughly before use, as filler may settle during prolonged storage.
2. Weigh 100 parts A component and add 5 parts RTV-3081 F catalyst (variation between 4% and 6% possible).
3. Mix the A and B components thoroughly by hand or mechanically until the catalyst is fully dispersed. Do not mix for an extended period and keep the temperature below 35°C.
4. De-air under vacuum if required; the mixture expands 3 to 5 times, so choose a large container. Excessive vacuum removes volatile components and may impair curing.
5. Pour the mixture onto the original within the pot life, avoiding air entrapment.
6. Allow to cure at room temperature (22 to 24°C); the mold can be demolded after a maximum of 6 hours and final properties are reached after 7 days. A lower temperature lengthens the cure time, while higher temperature and humidity shorten the pot life.

At 4% B component the material cures more slowly, giving air bubbles more time to escape. At 6% curing proceeds noticeably faster. Never mix more than you can process within the pot life.

For a brush-on or spatula mold, add 0.6 to 2% (typically 1%) Thixo C. This thickens the mixture so it can be applied with a spatula; in that case provide the mold with a support shell of plaster bandage, modeling epoxy or acrylic resin with glass fabric.

Note: This is an industrial product and is not intended for food contact, dental applications or skin molding.

Shelf Life

Stored cool, frost-free and in closed packaging, the shelf life is at least 1 year.

About the Manufacturer

Dow is a world market leader in the development and production of silicones for industrial and technical applications. The SILASTIC mold rubbers are known for their reliability and detail reproduction.

Professional Support

Unsure which catalyst, dosage or support-shell construction suits your application? Our specialists are happy to help. Contact us for personal advice on your mold or casting project.