Bluesil Silicones: An overview of the Elkem range
Rhodorsil and Bluesil are the two brands of Elkem Silicones (formerly Bluestar Silicones / Rhodia), one of the world's largest silicone manufacturers. While Rhodorsil is the traditional brand for silicone oils, pastes, and specialty products, Bluesil represents the modern product line of RTV-2 silicones, mold making materials, and technical elastomers. This guide explains the product range, provides technical data on the most important products, and helps you select the right silicone.
Rhodorsil and Bluesil: Two brands, one manufacturer
The history of the name reflects the history of the company:
- Rhodorsil: Original brand name of the Rhodia Group (now Elkem). Traditionally used for silicone oils (47V series), pastes, and specialty chemicals. The name has been established in the industry for decades.
- Bluesil: New brand introduced by Bluestar Silicones (now Elkem Silicones). Primarily refers to RTV silicones, mold building materials, and modern elastomers.
Bluesil RTV-2 silicones for mold making
The Bluesil RTV series includes both condensation-curing and addition-curing two-component silicones for professional mold making.
Bluesil RTV 3325 – Condensation-curing (standard for mold making)
RTV 3325 is a soft, highly elastic mold-making silicone with excellent tear resistance—the industry standard for detailed impressions.
| property | CATA 24H | CATA 6H | CATA SPE | CATA THIXO |
|---|---|---|---|---|
| Shore A hardness | 25 | 28 | 26 | 24 |
| Elongation at break (%) | 450 | 440 | 490 | 450 |
| Tensile strength (MPa) | 4,0 | 4,2 | 4,3 | 3,0 |
| Tear resistance (kN/m) | 21 | 26 | 25 | 21 |
Available catalysts:
- CATA 24H: Standard catalyst, colorless, pot life approx. 150 min., demolding time 24 h
- CATA 6H: Fast catalyst, colorless, pot life approx. 40 min., demolding time 6 h
- CATA SPE: Specially designed for EP resin resistance, colorless, pot life approx. 90 min.
- CATA THIXO: Thixotropic (stable), blue, pot life approx. 20 min. – for vertical painting
Mixing ratio: 100 parts RTV 3325 : 5 parts catalyst (by weight).
Processing: Mix both components at low speeds to minimize air entrapment. Vacuum degassing is recommended. Cross-link at 23 °C and 50% humidity.
Applications: Decorative elements (cornices, ornaments, statues, figures), candle and gift item molds, architectural elements (paving stones, columns), artistic foundries (lost wax casting process). Suitable for castings made of plaster, wax, acrylic resin, polyester resin, epoxy resin, and silicone elastomers.
Bluesil RTV 3428 – Addition-curing (food-safe)
The RTV 3428 is an addition-curing (platinum-catalyzed) mold-making silicone that is food-grade compliant – for applications that require zero shrinkage and maximum detail reproduction.
| property | value |
|---|---|
| network type | Addition crosslinking (platinum-catalyzed) |
| Shore A hardness | 28 |
| elongation at break | 400–450% |
| shrinkage | <0,1 % (nahezu schrumpffrei) |
| pot life | ~60 minutes |
| demolding time | 15–24 hours at 23 °C |
| food compliance | FDA, EU 1935/2004 |
Advantages over condensation cross-linking:
- Nahezu kein Schrumpf (<0,1 % vs. 0,5–1 % bei Kondensation)
- No by-products (no alcohol as with Sn catalysis)
- Food compliance possible
- Higher reproducibility in series production
- Heat acceleration possible (60–80 °C reduces curing time to 1–2 hours)
Applications: Food molds (chocolate, sugar, marzipan), medical technology prototypes, precision molds for synthetic resin casting, high-precision industrial molds where dimensionally stable impressions are critical.
Condensation vs. addition: Which type is right?
| criterion | Condensation (RTV 3325) | Addition (RTV 3428) |
|---|---|---|
| shrinkage | 0.5–1.0% | <0,1 % |
| Price | Cheaper | Higher |
| food contact | No | Yes (FDA, EU) |
| inhibition | Robust (few inhibitors) | Sensitive (sulfur, amines, tin) |
| Storage time for molds | Limited (shrinks after use) | Very long (dimensionally stable) |
| pot life | 20–150 min. | 30–120 min. |
| temperature resistance | Up to ~200 °C | Up to ~250 °C |
| Typical application | Decoration, architecture, art | Food, medicine, precision |
CAF series: Casting and potting silicones
The CAF series (Compound à Froid = cold-curing compounds) are condensation-curing RTV-2 silicones that have been specially developed for technical potting processes and electrical insulation.
The following table shows a comparison of the technical data for the four CAF variants:
| property | CAF 4 | CAF 33 | CAF 530 | CAF 730 MF |
|---|---|---|---|---|
| Color | Transparent | Transparent | Black | Transparent |
| Shore A hardness | 37 | 25 | ~34 | ~24 |
| Tensile strength (MPa) | 3,8 | 2,4 | 3,5 | ~2,0 |
| Elongation at break (%) | 290 | 500 | 450 | ~500 |
| Tear resistance (kN/m) | – | 6 | 15 | – |
| temperature range | – | – | -60 to +150 °C (+185 °C briefly) | -55 to +200 °C (+225 °C briefly) |
| Typical application | Electronics encapsulation, mold making | Optical encapsulation, transparent molds | UV-protected encapsulation, cable encapsulation | High-temperature casting |
Note: The CAF product numbers do not refer to the Shore hardness. CAF stands for "Compound à Froid" (cold-curing compound). The Shore hardness in the table above is decisive for the correct selection.
Bluesil silicone oils & pastes
Bluesil FLD 47V – Silicone oil series
The Bluesil 47V series comprises polydimethylsiloxane (PDMS) oils with various viscosities—the most widely used silicone oil series in the industry.
| Type | Viscosity (cSt) | Typical application |
|---|---|---|
| 47V 50 | 50 | Demolding, lubrication |
| 47V 100 | 100 | Release agents, damping oils |
| 47V 350 | 350 | Standard release agents, polishing agents |
| 47V 1000 | 1,000 | High-viscosity release agents, lubricants |
| 47V 12500 | 12,500 | Thixotropic additives, coatings |
| 47V 60000 | 60,000 | Thick coatings, anti-foam |
| 47V 100,000 | 100,000 | Rubber-like consistency, padding |
Properties of all 47V oils:
- Chemically inert and physiologically harmless
- Temperature resistant: -50 °C to +200 °C (briefly up to 300 °C)
- Water-repellent (hydrophobic)
- Oxidation-stable and UV-resistant
- Dielectric (electrically insulating)
- Food-grade and medically approved grades available
Applications: Release agents in injection molding and mold making, lubrication of plastic and rubber seals, cosmetic formulations, transformer oils, fluid dampers, textile finishing, polishing agents for automobiles and furniture.
Bluesil Paste 4 – Silicone paste
Bluesil Paste 4 is a highly effective silicone lubricating paste based on polydimethylsiloxane and amorphous silicon dioxide.
| property | value |
|---|---|
| Type | Silicone grease / silicone paste |
| base | PDMS + amorphous SiO₂ |
| consistency | Paste-like, white/translucent |
| temperature range | -40 °C to +200 °C |
| water resistance | Excellent (hydrophobic) |
| Chemical resistance | Resistant to water, weak acids, bases |
Applications: Seal maintenance (O-rings, valves, fittings), lubrication of plastic-on-plastic and plastic-on-metal sliding pairs, protection against moisture and oxidation, assembly aid for rubber seals, valve lubricant in the chemical and pharmaceutical industries.
Silbione – High-performance silicones for medical technology
The Silbione line is Elkem's premium brand for silicones in regulated industries, particularly medical technology and pharmaceuticals.
- Silbione Biomedical: LSR and HCR silicones in accordance with ISO 10993 and USP Class VI for implantable and body-contacting medical devices
- Silbione Pharma: Pharmaceutical and packaging silicones compliant with FDA and EMA regulations
- Silbione Film & Coating: Thin-film silicones for release liners, coatings, and self-adhesive tapes
For detailed information on biocompatible silicones, read our Biocompatible Silicones: ISO 10993 and USP Class VI Guide.
Bluesil FLD – Liquid silicones (LSR)
The Bluesil FLD series comprises liquid silicone rubbers for injection molding. These 2K systems are processed automatically in injection molding machines with metering pumps.
Advantages of LSR processing:
- Short cycle times (30–120 seconds)
- High reproducibility and batch consistency
- Burr-free production thanks to low viscosity
- Suitable for automation in large series production
- Temperature resistant: -148 °F to 392 °F
Applications: Seals, membranes, baby pacifiers, medical tubing, keyboard mats, automotive seals, LED optics.
Silcolapse – silicone defoamer
Elkem's Silcolapse range includes silicone defoamers for industrial processes:
- Silcolapse 5020: 20% active silicone emulsion – defoamer for aqueous systems. Used in textile, paper, and wastewater treatment.
- Silcolapse 416: 100% active silicone compound – high-performance defoamer, effective at 1–100 mg/kg. Used in chemical processes and fermentation.
Choosing the right product line
| Application | Recommended product line | Specific product |
|---|---|---|
| Mold making (decoration, art) | Bluesil RTV | RTV 3325 + CATA 24H |
| Mold making (fast) | Bluesil RTV | RTV 3325 + CAT 6H |
| food forms | Bluesil RTV | RTV 3428 |
| Electronics encapsulation (black) | CAF series | CAF 530 (Shore A 34, UV protection) |
| Electronics encapsulation (clear) | CAF series | CAF 33 (Shore A 25) or CAF 4 (Shore A 37) |
| High-temperature casting | CAF series | CAF 730 MF (up to +200 °C) |
| release agent | Rhodorsil 47V | 47V 350 or 47V 1000 |
| Seal maintenance | Rhodorsil paste | Paste 4 |
| medical technology | silbione | Silbione Biomedical LSR |
| Injection molding (series) | Bluesil FLD | Bluesil FLD 47/50 |
| process defoaming | silcolapse | Silcolapse 5020 |
Frequently asked questions (FAQ)
What is the difference between Rhodorsil and Bluesil?
Both brands belong to Elkem Silicones. Rhodorsil is the older brand name (Rhodia Group) and is mainly used for silicone oils and pastes. Bluesil is the newer brand (Bluestar Silicones, now Elkem) for RTV silicones and modern elastomers. Both brands remain in use in parallel.
Which Bluesil silicone is suitable for food molds?
Bluesil RTV 3428 (addition-curing) is food-safe in accordance with FDA and EU 1935/2004. It is used as standard for chocolate, sugar, and marzipan molds. The condensation-curing RTV 3325 is not suitable for food contact.
Which silicone oil should be used as a release agent in mold making?
For standard release agent applications, we recommend Rhodorsil 47V 350 (medium viscosity). For thicker films and higher lubricity: 47V 1000. Lower viscosity for spray applications: 47V 50 or 47V 100.
How long does a mold made from Bluesil RTV 3325 last?
When used properly (release agent, no excessive heat), an RTV-3325 mold typically achieves 50–200 casts, depending on the casting medium. With aggressive polyester resin, this is more likely to be 50 casts, while with plaster or wax it can be up to 200. The mold should be stored in a cool, dark place.
Can I use Bluesil RTV 3325 with epoxy resin casting?
Yes, but use the CATA SPE catalyst. This is specially formulated for resistance to epoxy resins. With standard CATA 24H, the mold may degrade more quickly with frequent contact with EP resin.
What does CAF mean in silicones?
CAF stands for "Compound à Froid" (French for "cold-curing compound"). The product numbers are not Shore hardness specifications: CAF 4 has Shore A 37, CAF 33 has Shore A 25, CAF 530 has Shore A ~34. The correct selection always requires a look at the technical data sheet.
Elkem products at SILITECH
- Stock items in Switzerland for the most popular products
- Technical advice from our silicon engineers
- Sample deliveries for your evaluation
- Support with product conversion and process optimization
Contact us for a product recommendation or a quote.
