Wacker Elastosil® M 4470 + Catalyst T 40 – Hard Condensation Silicone for Metal Casting & Industrial Moulding

Heat-Resistant Hard Condensation Silicone for Molds for Low-Melting Metal Alloys and Industrial Reproduction Applications

Wacker ELASTOSIL® M 4470 is a pourable, room-temperature curing condensation silicone (tin-cure) for the production of molds for casting low-melting metal alloys such as tin, lead, and zamak (max. melting point 300°C). The product cures into a firm rubber mold with a Shore A hardness of 60, a reddish-brown color, and excellent thermal stability and heat conductivity. The linear shrinkage is 0.8% — inherent to condensation curing. With Catalyst T 40, the processing time is approximately 40 minutes, and the mold is tack-free after 3–4 hours at 23°C and 50% relative humidity. The mixing ratio is 100:2 (base:catalyst) by weight.

ELASTOSIL® M 4470 is particularly suitable for applications where dimensional flexibility is more important than zero shrinkage, and where high temperature resistance, high hardness, and good heat dissipation are essential. Not suitable for food-safe applications (no BfR/FDA conformity).

Key Benefits

• Shore A hardness 60 – high and rigid: The high hardness ensures dimensionally stable molds with minimal distortion during demolding, ideal for molds with few undercuts.
• Thermally stable for metal casting up to 300°C melting point: Its excellent thermal stability makes the product suitable for casting low-melting metal alloys. This concerns short contact with the molten alloy in a thin-walled mold on an aluminium plate, not continuous exposure. For continuous service the limit is around 180 to 200°C. Before use, the mold should be post-cured at 150°C for several hours for optimal outgassing.
• Thermally conductive – rapid heat dissipation: The high filler content (quartz 40–50%) ensures efficient heat dissipation, which shortens cycle times in metal casting.
• High swelling resistance to casting resins: Excellent resistance to polyesters, epoxies, and polyurethanes makes the product versatile for reproduction molds.
• Pot life ~40 min (with T 40) – workable processing time: Sufficient time for careful mixing, degassing, and pouring, even for larger mold volumes.
• Good flowability and self-deaeration: Low viscosity of 15,000 mPa·s and self-venting properties ensure bubble-free molds.

Typical Applications

• Molds for casting tin miniatures, sinkers, fishing lures, and fishing hooks
• Molds for low-melting metal alloys (tin, lead, zamak, maximum melting point 300°C)
• Thin-walled molds placed on an aluminum plate for optimal heat dissipation during metal casting
• Reproduction molds with high rigidity for foam resin casting (PU foam; recommended: apply a barrier layer)
• Molds with high swelling resistance for polyester casting resins
• Industrial molds and mold inserts where high temperature resistance is required

Processing Instructions

1. Stir the base component ELASTOSIL® M 4470 thoroughly before use — the quartz filler may settle.
2. Weigh 100 parts by weight of base and add 2 parts by weight of Catalyst T 40. At 2% T 40 the pot life is approximately 40 minutes and the mold is tack-free after 3 to 4 hours. A higher dosage shortens the pot life. For a longer processing time, use Catalyst T 37 at 3%, which gives a pot life of approximately 80 to 100 minutes with a cure time of 10 to 12 hours.
3. Mix slowly and thoroughly for at least 3 minutes. Scrape the sides and bottom of the mixing container.
4. Optional: degas in a vacuum chamber (10–20 mbar) for 5–10 minutes.
5. Pour within the pot life into the mold from the lowest possible height to minimize air entrapment.
6. Allow to cure at room temperature (23°C, min. 40% RH) for 3–4 hours (tack-free) up to 24 hours for full mechanical properties.
7. Post-curing recommended before metal casting: several hours at 150°C to release residual gases. The first castings may have a pimply surface due to residual gases — these should be removed.
8. Optional for metal casting: apply a thin layer of silicon carbide, graphite powder, or acetylene black to the mold surface for better wetting by the liquid metal.

Thin-walled molds are most suitable for metal casting and should be placed on an aluminum plate or other heat-conductive material.

Manufactured by Wacker Chemie AG, a global market leader in the development and production of silicones for industrial and technical applications.

Important Warning: Condensation Silicone – Shrinkage and Humidity

Please note: This is a condensation silicone (tin-cure). Unlike addition silicones, condensation silicones exhibit a linear shrinkage of 0.4–0.8% due to the alcohol released during crosslinking. For dimensionally critical applications, an addition silicone is the better choice. Ensure a relative humidity of at least 40% during processing — at lower humidity, the surface may remain sticky. Do not add water to the mixture. The catalyst T 40 contains a tetraorganotin compound, is flammable and can cause eye and skin irritation — consult the catalyst's SDS for complete safety measures.

Professional Support

ELASTOSIL® M 4470 is available in a kit format including Catalyst T 40. For longer pot lives, you can also use Catalyst T 37 (3% dosage, pot life 80–100 minutes, cure time 10–12 hours). Please contact us for technical datasheets, processing instructions, or product advice.