Dow SILASTIC RTV-3481 Fast – Dry Condensation Mould 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-cure (RTV-2) mould rubber that cures at room temperature into a strong, dry silicone rubber. The set combines RTV-3481 Part A with the fast RTV-3081 F catalyst, mix ratio 100:5 by weight. With a Shore A hardness of 23, an off-white final colour and a pot life of 30 to 45 minutes at 23 °C, the material is highly flowable and self-degassing. Final mechanical properties are reached after 7 days. The rubber is ideally suited to the detailed reproduction of figures and ornaments, to model-making, and to moulds 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 mould 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 demoulding 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 – demould after max. 6 hours: short turnaround thanks to the fast RTV-3081 F catalyst.
• Highly flowable – 22,100 mPa·s mixture: self-degassing and easy to pour around fine details.

Typical Applications

• Moulds for concrete and concrete ornaments
• Moulds 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 Part A thoroughly before use, as filler may settle during prolonged storage.
2. Weigh out 100 parts of Part A and add 5 parts of RTV-3081 F catalyst (can be varied between 4% and 6%).
3. Mix Part A and Part B thoroughly by hand or mechanically until the catalyst is fully dispersed. Do not mix for too long and keep the temperature below 35°C.
4. Degas under vacuum if required; the mixture expands 3 to 5 times, so choose a large container. Degassing for too long 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); you can demould 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% Part B 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-applied mould, add 0.6 to 2% (typically 1%) Thixo C. This thickens the mixture so it can be applied with a spatula; in that case, give the mould a support shell of plaster bandage, kneadable epoxy or acrylic resin with glass fabric.

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

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 mould 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 mould-making or casting project.