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TSR21 - Mould-making silicone
201362401
€25.00
30,25 € Tax incl.
30,25 € Tax incl.
This product cannot be shipped by air. To the Canary and Balearic Islands it is sent by sea freight only, with a longer delivery time.
Condensation (tin) silicone Shore A25. Ratio 100:10, 60 min working time. Resistant to epoxy, polyurethane and polyester resins. 2 catalysts available. Developed by Polytek, of which we are official distributors, to meet the needs of the most demanding customers in our market.
TSR21 is a Shore A25 tin-cure (condensation) silicone formulated for production mould-making, offering high tear strength and good chemical resistance. Available with two catalyst speeds — STANDARD and FAST — it adapts to any workshop pace, from large pieces that need generous handling time to short runs where cycle time is the priority. Developed by Polytek, of which we are official distributors, to meet the needs of the most demanding customers in our market.
Technical specifications
| Parameter | STANDARD Catalyst | FAST Catalyst |
|---|---|---|
| Mix ratio (by weight) | 100 Base : 10 Catalyst | 100 Base : 10 Catalyst |
| Working time at 23 °C | 60 minutes | 30 minutes |
| Demould time at 23 °C | 24 hours | 5 hours |
| Shore Hardness A | 25 | |
| Cure type | Condensation (tin) | |
| Tear strength | High | |
| Chemical resistance | Excellent, with reduced skinning | |
| Heat resistance | Improved over conventional tin silicones | |
| Shelf life | Long, with stable release properties | |
What it's used for
TSR21 is designed for the repeated production of flexible moulds in professional workshops, with good release properties and resistance to demanding casting materials:
- Moulds for casting polyester resin, epoxy resin and polyurethane resin
- Moulds for polyurethane foams
- Moulds for plaster
- Moulds for wax and soap
- Reproduction of decorative pieces, figures and set-dressing elements in series
- Prototyping and duplication of originals in professional workshops
How to use it
- Prepare the original: make sure the original piece is clean, dry and free of dust. If it's porous (plaster, wood, ceramic), apply one or two coats of Ferosil V 32 release agent and let it dry completely before pouring the silicone.
- Build the mould box: surround the original with a sealed mould box, leaving at least 10–15 mm of margin around and above the piece.
- Weigh the base: calculate the required amount of TSR21 Base and weigh it precisely with a scale accurate to at least 1 g.
- Add the catalyst: add the chosen catalyst (STANDARD or FAST) at a ratio of 10 parts per 100 parts of base, by weight. If you need more thixotropy for brush application, add Thixo Additive before mixing.
- Mix slowly: stir for 3–5 minutes with slow movements, scraping the sides of the container to ensure a homogeneous mix and minimise air entrapment.
- Pour the silicone: pour in a thin, continuous stream from the lowest point of the mould box, letting the silicone rise and cover the original on its own.
- Let it cure: respect the demould time for the chosen catalyst: 24 hours with STANDARD and 5 hours with FAST. Don't force demoulding early.
- Demould and prepare for casting: carefully remove the mould, clear away any mould box residue and let it rest for at least 1 additional hour before the first cast.
Usage tips
Choose the catalyst that matches your workflow
The STANDARD catalyst (60 min working time, 24 h demould) is the most versatile: it lets you degas in a vacuum chamber, fill complex mould boxes or work large pieces without rushing. FAST (30 min, 5 h) speeds up production without losing too much working margin. Never mix catalysts together.
Temperature and humidity affect cure
Condensation silicones cure through reaction with ambient humidity. Higher temperature and relative humidity speed up curing; below 15 °C the process can take considerably longer. The times given are indicative at 23 °C. In winter or workshops with heavy air conditioning, add a safety margin to the demould time.
Pigmentation and viscosity adjustment
You can colour TSR21 with silicone-compatible pigments at a maximum of 3% by weight of the total mix. If you need a thicker texture for brushing vertical or detailed areas, use Thixo Additive to increase thixotropy without compromising cure.
Frequently asked questions
What's the difference between the two catalysts?
The difference is working time and demould time. STANDARD gives 60 minutes working time and 24 hours demould; FAST reduces this to 30 minutes and 5 hours. Final hardness (Shore A25) is the same with both.
How many copies can I get from a TSR21 mould?
Under normal use with resins you can expect several dozen copies. The mould's lifespan depends on the material cast, its chemical aggressiveness and how carefully it's demoulded. For very long runs, consider a platinum silicone.
Can I use this silicone for food applications?
No. TSR21 is a tin-cure (condensation) silicone and is not food-grade certified. For chocolate, baking or ice-cube moulds, use an FDA-certified platinum silicone instead.
Can I cast platinum silicone inside a mould made with TSR21?
No. Tin silicone inhibits the cure of platinum (addition) silicones. If you need final pieces in platinum silicone, the mould must also be platinum.
Do I need to apply a release agent before pouring the silicone?
It depends on the original's material. On non-porous surfaces (metal, ABS plastic, already-cured resin) TSR21 generally doesn't stick. On porous materials (plaster, wood, unglazed ceramic) it's essential to seal the surface with a release agent such as Ferosil V 32.
Can I add more catalyst to speed up the cure?
This isn't recommended. Increasing the catalyst ratio above 10% doesn't significantly speed up cure and can result in a mould with worse mechanical properties. If you need more speed, choose the FAST catalyst directly.
What sizes is TSR21 available in?
TSR21 is available in 1 kg, 5 kg and 20 kg, each with two catalysts (STANDARD and FAST), for a total of 6 combinations. The 1 kg size is ideal for testing, 5 kg suits medium-output workshops, and 20 kg offers the best price per kilo for continuous production.
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