PlatSil® FS-20 Platinum Cure Silicone Rubber
PlatSil® FS-20 is a fast-setting, platinum-cure silicone rubber designed for professional mould making applications where rapid turnaround and durability are essential. This two-part RTV silicone features a simple 1:1 mix ratio by weight, an approximately 8-minute working time and a demould time of around 25* minutes at room temperature.
Unlike many fast-curing silicones, PlatSil® FS-20 provides a generous working time relative to its cure speed, allowing sufficient time for mixing and pouring while still delivering exceptionally fast production cycles. Its low viscosity of approximately 3,800 cP allows it to flow easily into fine details, making it suitable for highly detailed moulds, brush-on mould systems and complex geometries.
Once cured, PlatSil® FS-20 produces a milky white rubber with a Shore OO66 / Shore A20 hardness, offering an excellent balance of flexibility, strength and tear resistance. The platinum-cure system provides excellent dimensional stability with virtually no shrinkage, making it suitable for demanding production environments where accuracy, durability and repeatability are important.
Key Features
- Easy 1:1 mix ratio by weight or volume.
- Fast demould time of approximately 25 minutes.
- 8-minute working time relative to cure speed.
- Low viscosity of approximately 3,800 cP for easy pouring and excellent detail reproduction.
- High tear strength for durable, long-lasting moulds.
- Flexible Shore OO66 / Shore A20 rubber.
- Excellent dimensional stability with virtually zero shrinkage.
- Can be thickened with Sil-Thix for brush-on mould applications.
- Heat may be used to further accelerate curing.
- Good chemical resistance for extended mould life.
- Excellent release properties against many common casting materials.
Typical Applications
- Special effects (SFX) mould making.
- Theatrical and film production moulds.
- Medical simulation props and training aids.
- Brush-on blanket moulds for complex shapes.
- Rapid prototyping and product development.
- Architectural model production.
- Automotive and industrial prototyping applications.
- Fast-turnaround production mould making.
Compatible Additives
PlatSil® FS-20 can be modified to suit specific project requirements using a range of additives:
- Sil-Thix – Thickens the silicone for brush-on mould making and vertical surfaces.
- Silicone Pigments – Colour the silicone for identification or special effects applications.
- PlatSil® Retarder – Extends working time when additional processing time is required.
- PlatSil® Accelerator – Reduces working and cure times for even faster production cycles.
Available Sizes
- 1kg Kit
- 10kg Kit
- 80lb Kit
Important Information
As with all platinum-cure silicone systems, certain materials may inhibit cure. Contamination from sulfur-containing materials (including some sculpting clays), amines, tin compounds, polyester resins, certain paints and some silicone rubbers may cause inhibition. If compatibility is unknown, a small-scale test is recommended before commencing production.
What is the difference between PlatSil® FS-20 and standard platinum cure silicones?
PlatSil® FS-20 is designed for fast production environments. It offers an approximately 25-minute demould time while still providing around 8 minutes of working time. Its Shore A20 hardness provides a balance of flexibility and strength, making it suitable for detailed moulds requiring durability and fast turnaround.
Can PlatSil® FS-20 be used for brush-on moulds?
Yes. Although PlatSil® FS-20 is supplied as a pourable silicone, it can be thickened using Sil-Thix to create a brushable consistency for blanket moulds and complex vertical surfaces. Sil-Thix can be added at up to 5% by weight. When applying multiple layers, subsequent coats should be applied while the previous layer is still partially cured to ensure good adhesion.
Can I vacuum degas PlatSil® FS-20?
Yes. PlatSil® FS-20 can be vacuum degassed, but care should be taken due to its short 8-minute working time. Be mindful of the quantity being mixed and the time required for degassing, as larger batches may take longer to process. Smaller batches are recommended to ensure sufficient time for mixing, degassing and pouring before the silicone begins to cure.
How long does PlatSil® FS-20 take to cure?
At approximately 23°C, PlatSil® FS-20 typically reaches demould strength in around 25 minutes. Cure times may vary depending on temperature and environmental conditions. Lower temperatures will extend curing times, and curing below 15°C is not recommended.
Can heat be used to speed up the cure?
Yes. Gentle heat can be used to accelerate the curing process and further reduce demould times. Temperatures should not exceed 60°C. PlatSil® Accelerator can also be used to shorten curing times, although this will reduce the available working time.
Can I colour PlatSil® FS-20?
Yes. Silicone pigments can be added to PlatSil® FS-20 to produce a wide range of colours for mould identification, special effects work or production applications. Pigments can be added at up to 0.5% of the total mixed weight and should be incorporated into Part B before mixing with Part A.
What materials can be cast into PlatSil® FS-20 moulds?
PlatSil® FS-20 moulds can be used with polyurethane resins, epoxy resins, polyester resins, polyurethane foams, wax, plaster and other casting materials. While silicone generally offers excellent release properties, a suitable release agent or barrier coat may be recommended to extend mould life, particularly when casting resins.
Does PlatSil® FS-20 shrink during cure?
No. As a platinum-cure silicone, PlatSil® FS-20 exhibits virtually no shrinkage during curing, helping to maintain excellent dimensional accuracy and consistent reproduction of fine details.
What hardness is PlatSil® FS-20?
PlatSil® FS-20 cures to a Shore OO66 / Shore A20 rubber, making it the firmest silicone in the FS-Series range. It provides greater rigidity than FS-00 and FS-10 while retaining good flexibility and tear resistance for mould making applications.
What can cause cure inhibition?
Some materials can interfere with the curing process of platinum-cure silicones. Common sources of inhibition include sulfur-containing clays, amines, tin compounds, polyester resins, certain paints and some silicone rubbers. If compatibility is uncertain, a small test should be performed before mould making.
Can I extend the working time?
Yes. PlatSil® 71R Retarder can be added to increase the working time when additional time is required for large moulds or complex pours. Adding approximately 1% Retarder by total mixed weight roughly doubles the working time, while 2% can approximately triple it. Do not exceed 4%, as this may prevent the silicone from curing.
Can I make the cured silicone harder?
PlatSil® FS-20 is already the firmest grade in the FS-Series, with a Shore A20 hardness. If a harder silicone is required, we recommend reviewing alternative platinum-cure silicones in our range to find a product with the appropriate hardness, working time and physical properties for your application.
