Premium Flexible Polyurethane Casting Elastomer for Professional Mold Making and Prototyping Applications

Polyurethane Casting System Flexible A40 is a two-component polyurethane casting elastomer that cures at room temperature into a permanently elastic end product with a hardness of Shore A 38 to 42 and an amber appearance. The system combines a very high elongation of more than 1000% with good tear strength and is easy to process. With a pot life of 23 to 27 minutes (100 ml, 40 mm, 25°C), a demold time of 15 to 18 hours and a mixing ratio of 100:50 (A:B) by weight, it offers reliable, straightforward processing. Final properties are reached after 7 days at 25°C. Polyurethane is generally more wear resistant than silicone but more sensitive to UV and temperature, which makes this system particularly suitable for plaster and cement molds, elastomeric components of medium hardness and prototyping work.

Key Benefits

• Hardness Shore A 38 to 42: medium hardness and permanently elastic – firm enough to hold shape, supple enough to release undercuts.
• Elongation at break > 1000%: extremely stretchable – complex geometries can be demolded without tearing or permanent deformation.
• Pot life 23 to 27 minutes: generous working time at 100 ml – enough time to weigh, mix, degas and pour.
• Demold time 15 to 18 hours: demoldable within a day cycle – the mold can be taken off the model the next working day.
• Negligible shrinkage: dimensionally stable castings – accurate reproduction of the original without corrective finishing.
• Max. recommended pour thickness 50 to 60 mm: thick layers possible – for large thicknesses pour a small volume or work in several layers to limit heat build-up.

Typical Applications

• Molds for plaster, cement and concrete work in construction, decoration and reconstructed stone
• Elastomeric components of medium hardness for technical applications
• Prototypes and pre-series in design and product development
• Foundry patterns and fixing of molds
• Replicas and demonstration models
• Small flexible castings requiring high elongation and tear strength

Processing instructions:

1. Stir or shake both components thoroughly in their original packaging. Fillers and moisture absorbers can settle; shake the packaging intensively before use.
2. Process the product only at room temperature (20 to 25°C) in a dry room above 15°C. Pour onto dry models that are sealed against moisture and do not use wooden spatulas.
3. Clean the model thoroughly, treat it with a suitable sealer and apply an appropriate release agent.
4. Weigh the components accurately at a ratio of 100 parts A to 50 parts B (by weight), or 100 to 45 by volume. A deviation of more than 3% means the stated specifications will not be achieved; for small quantities use a scale accurate to 0.01 grams.
5. Combine components A and B and mix thoroughly and homogeneously. Use a mixing bucket with a large surface area to maximise working time. Pouring can be done under vacuum or at atmospheric pressure.
6. Pour the mixture within the pot life in a steady stream into the mold and avoid trapping air. For castings thicker than 20 mm, pour several successive layers to limit heat build-up; allow each layer to set before the next.
7. Wait 15 to 18 hours before demolding. Thermal and mechanical properties develop quickly; final specifications are reached after 7 days at 25°C. No post-curing is required.

Supplied by Silicones and More, specialist in high-quality mold rubbers and casting materials for professional makers.

Mandatory Diisocyanate Training

The A component contains diisocyanates. Since 24 August 2023, adequate training is mandatory for industrial and professional use of products with a diisocyanate content above 0.1%. Make sure everyone working with this product has completed the required training before putting it into use. You can register directly through the official ISOPA platform at safeusediisocyanates.eu, where the trainings are available in all EU languages.

Shelf Life

Store both components in their original, closed packaging in a cool and dry place. Stored this way, resin and hardener have a shelf life of one year. The resin is moisture sensitive, which can cause the product to thicken or solidify; use opened packaging as quickly as possible.

Professional Support

Polyurethane Casting System Flexible A40 is the choice for makers and technicians who need flexible, tear-resistant molds and castings of medium hardness with high detail reproduction. Contact us for technical datasheets, processing guides or product advice.