Elkem silicones: the complete product range at a glance

Bluesil, Silbione, Silcolapse — three brands, one manufacturer. This guide explains how the product range is actually organized, which product solves which task, and where the differences become truly relevant in practice. It is based on the 155 products that SILITECH AG stocks and distributes in Switzerland, supplemented by the manufacturer's official technical data sheets.

Notice regarding the change of ownership in 2026: On February 13, 2026, Elkem ASA announced the sale of a majority stake in its Silicones division to Bluestar (China National Bluestar Group). The Annual General Meeting approved the sale on March 9, 2026, and the transaction is expected to be completed by the end of April/beginning of May 2026. For SILITECH customers: Plants, formulations, and delivery capabilities will remain unchanged (details in section 1.2). Product names and branding may change in the medium term.

1. Manufacturer and brand logic — as of 2026

The manufacturer behind Bluesil, Silbione and Silcolapse is one of four globally integrated full-scale silicon producers (alongside Dow, Wacker and Shin-Etsu) — plants in Roussillon (FR), York (USA), Jiangxi (CN), Chakan (IN) and other locations.

1.1 Historical sequence of names

The same product line has had four names in industrial history:

Rhodorsil, Bluestar Silicones, and Elkem Silicones technically refer to the same product lines in different company eras. If you still know a product as "Rhodorsil RTV" or "Bluestar RTV," the current equivalent is the Bluesil product of the same name.

1.2 Change of ownership in 2026 — what customers need to know

Closing at the end of April/beginning of May 2026. From a customer perspective, this is a change of ownership, not a product change: plants, recipes, and formulations remain the same. Short-term effects and risks for SILITECH customers:

1.3 Current Brand Logic

Practical rule: The brand name indicates the use case , not the chemical composition. A Silbione RTV and a Bluesil RTV can be chemically almost identical—the difference lies in documentation, regulatory requirements, and quality control. Those who don't manufacture medical devices often end up paying for Silbione documentation they never need. Those who do manufacture medical devices are not permitted to use Bluesil.

2. The product range is divided into 18 product groups

2.1 Elkem's official product taxonomy ↔ SILITECH range

Elkem Silicones itself categorizes its products into nine main categories (plus upstream raw materials and sustainability lines). First, the translation, so that readers coming from elkem.com can find their way around:

Outside of Elkem's main categories, but within the SILITECH range: catalysts (6), additives/inhibitors/primers/diluents (10), Silcolapse defoamers (5) — see chapters 11, 12, 15.

2.2 18 pragmatic product groups (SILITECH classification)

The 155 products currently offered by SILITECH AG can be divided into 18 distinct groups for this reference work. These groups represent the Elkem taxonomy in greater detail—for example, "RTV-2" is split into mold making / electronic potting / medical, because the application and selection logic differ in each category

3. Bluesil RTV-2 — the mold-making core

RTV-2 stands for Room Temperature Vulcanizing, Two Component: Two components that crosslink to form an elastomer after mixing at room temperature. Two fundamental chemistry processes compete, and the choice between them shapes material selection and process more than any other parameter.

3.1 Condensation vs. Addition — the crucial difference

Honest assessment. Additive coating is almost always the cleanest solution from a technical standpoint—unless the application requires robust crosslinking against contamination, or the cost of a platinum system is prohibitive. Condensation RTV-2 coatings are not "inferior," they are more tolerant —which is the crucial point in many real-world workshops.

3.2 The most important product families in detail

Bluesil RTV 141 / 147 / 148 — The workhorse trio (additional networking). The three are often confused, but belong to different applications.

• RTV 141 — Shore A 50, transparent, η ≈ 4,000 mPa·s, pot life 4 h, demolding time 36 h. Clear elastomer for applications where it is necessary to see through the body (light guides, optical prototypes, membrane seals).
• RTV 147 — Shore A 60, harder, η_A ≈ 150,000 mPa·s (paste-like), pot life 2 h. For small and medium-sized molds with high requirements for edge stability.
• RTV 148 — Shore A 40, softer than 147, η ≈ 10,000 mPa·s, pot life 4 h. Typically with RTV 147 B (cross-compounding) to achieve intermediate hardnesses.

Bluesil RTV 3040 / 3041 — the transparent, high-performance duo. Two-component, addition-curing, Shore A 38. RTV 3040 is the widely used clear elastomer with η ≈ 70,000 mPa·s; RTV 3041 is the variant with a shorter pot life (75 min vs. 120 min). Both are industry standards for clear prototype shapes and technical inlays.

Bluesil RTV 3325 / 3325P — the classic for condensation curing. Shore A 25, elongation at break up to 450%, tear strength 21 kN/m, tensile strength 4.0 MPa (measured after 96 h at 23 °C with CATA 24H). The standard for detailed decorative molds, because its tear strength allows for the demolding of complex undercuts.

The catalyst determines pot life and curing:

Bluesil RTV 3428 — the precision addition alloy. Shore A 28, pot life 60 min, demolding time 16 h. Use where the condensation shrinkage of a 3325 alloy exceeds tolerances. Typical applications: precision casting with plaster or ceramics, industrial molds for investment metal casting.

Bluesil RTV 3410 / 3535 / 3720 — Quick-cure family. Addition, pot life 3–15 min, demolding 15–35 min. For series production with short cycles — e.g., automated casting. Important: These rapid-curing resins are sensitive to surface contamination; any trace of sulfur or tin soap will poison the platinum catalyst.

Bluesil RTV 3440 / 3445 / 3450 — the medium hardness class for technical molds. Shore A 40–50, η ≈ 13,000–15,000 mPa·s, variable pot life (60–90 min), demolding time 6–16 h. The sweet spot for industrial production molds subjected to mechanical stress.

Bluesil RTV 8352 LV A — the low-viscosity system. Shore A 55, η = 2,200 mPa·s. Flows deep into undercuts, cures overnight. Ideal for components with complex geometries where bubble-free results are crucial.

3.3 Overview of the product families — Bluesil RTV-2 Mold making

All values ​​are taken from the official Elkem TDS. One line per product family; the variants in the range (A, B, different colors and packaging) share the same chemical composition and specifications.

Product variants in the SILITECH range (A/B components, colored B variants such as pink/white/black/translucent, containers from 1 kg to 200 kg) share the characteristic data of the respective family.

3.4 Mechanical properties — RTV-2 mold making

For the design of mechanically stressed molds and technical castings.

For the sake of completeness: The electrical characteristics (dielectric strength, volume resistance, tan δ) are crucial for electronic potting — see Chapter 6 (ESA) and dedicated TDS.

4. Bluesil RTV-2 Specialties (Pouring, Dielectric, High Temperature)

Besides mold making, Elkem uses RTV-2 chemistry for potting, dielectric, and high-temperature applications. The distinction is purely functional—chemically, these products are closely related to the mold making series.

Bluesil RTV 3040 / 3041 — already discussed in section 3.2.

Bluesil RTV 3132 — fast-curing casting elastomer. Shore A 32, pot life 15 min, demolding time 2 h. For serial potting in electronics, where fast cycle times are crucial.

Bluesil RTV 3221 — the soft standard. Shore A 18, pot life 30 min. Used for damped bearings and mechanically stressed seals with low compression set.

Bluesil RTV 3255 + Cat. XY-86 — for high temperatures. Shore A 55, pot life 3 h, Tmax up to 300 °C for short periods. For use near engines, exhaust systems and furnaces.

Bluesil-V-695 / V-1062S — specialty electro-dielectric elastomers. The V-series indicates vulcanizing-specific formulations; often with barrier properties for cable and coil potting.

Table — Bluesil RTV-2 other (19 products)

5. CAF series — one-component sealing and adhesive elastomers

CAF stands for Caoutchouc Silicone à Vulcanisation à Froid (cold-curing silicone elastomer) — the abbreviation originates from the French Rhodia line. All CAF products are single-component, moisture-curing: Applied from the cartridge, the material forms a skin within minutes upon contact with atmospheric moisture and cures layer by layer (approx. 2–3 mm per 24 h at 23 °C and 50% RH).

Let's clear up a misconception. The CAF number says nothing about the Shore hardness. CAF 4 has Shore A 37, CAF 33 has Shore A 25, CAF 530 has Shore A 34. Choosing based solely on the number regularly leads to the wrong choice. Always choose based on the TDS (Total Data Set).

5.1 The most important CAF types in practice

CAF 1 / CAF 4 — the standard all-rounders. Neutral-curing (oxime- or alkoxy-based), some products are acetoxy-releasing — insurers in electronic applications read this information carefully because acetic acid attacks copper components. For metal and electronic contacts, use only neutral CAF (oxime/alkoxy)

CAF 3 / CAF 30 / CAF 33 — the switches. Shore A 20–26. Typical use in expansion joints, glass seals, sanitary areas (CAF 30 and 33 are available in transparent, white, black).

CAF 530 — the adhesive and sealant with a bonding profile on glass, metal, and plastic. Shore A 34, tensile strength 3.5 MPa, elongation at break 450%, tear propagation 15 kN/m, Tmax +150 °C (+185 °C for short periods). Important: CAF 530 is not suitable for continuous high-temperature applications — for these, use CAF 33 or CAF 730.

CAF 730 MF — the classic high-temperature fluid. Shore A 25, Tmax +200 °C (+225 °C briefly). MF = Medium Flow, but flows under slight pressure. Oven door seals, exhaust systems, thermal processing machines.

CAF 99 AXAD — the extreme. Shore A 51, Tmin −70 °C, Tmax +250 °C (+300 °C briefly). AXAD variant for demanding high and low temperature applications with mechanical stress.

CAF 7037 MF — the neutral medium. Shore A 24, Tmax +225 °C, neutral crosslinking (suitable for metal/electronics).

5.2 Overview of the CAF families

5.3 Mechanical and curing characteristics of the CAF series

Skin formation time and curing time of 24 hours are crucial during processing — they determine the application timeframe and the layer-by-layer curing rate at ambient humidity (23 °C, 50 % RH).

Notes. CAF 1 has the highest tensile strength of the standard series, CAF 530 the highest tear resistance and the highest dielectric strength—hence its preference for adhesive applications. CAF 33 is the classic elongation option (500%), suitable for expansion joints. CAF 99 AXAD is the mechanically strongest and thermally most extreme (Shore 51, Tmax 250 °C).

6. Bluesil ESA — 2K-Pt addition: potting compound, dielectric, bonding

The ESA series (Elastomère Silicone Adhésif) is Elkem's line for potting, embedding, and adhesive sealing in the electronics and electrical industries. Chemistry: 2K, Pt-catalyzed polyaddition. Depending on the type, the system cures at room temperature (with optional heat acceleration) or exclusively under heat (ESA 7244). ESA is not injection molded but cast, dispensed, or potted; LSR injection molding is a separate Elkem line (not included in the SILITECH range).

The five ESA families in the product range cover very different applications — the values ​​are not uniform, but vary significantly for each type. Key differences:

• ESA 6110 — RT-curing, optically clear silicone gel (no measurable tensile strength). Softest type in the series, 1:1, QC version with a 5-minute pot life.
• ESA 7244 — hot-curing 2K adhesive elastomer (80–200 °C), very long pot life (>16 h at 23 °C), thermally conductive (0.40 W/m·K), flame retardant (FV-1), ISO R 868 Shore A 50.
• ESA 7250 E5 — RT-curing, optically clear, high-strength elastomer (tensile strength 6.2 MPa, elongation 115%), ratio 10:1, accelerating.
• ESA 7252 — RT-crosslinking, black/white flame-retardant, thermally conductive potting compound (λ 0.42 W/m·K), ratio 1:1, pot life 1.5 h, curing 8 h @ 23 °C.

6.1 Per-Variant Characteristics

Processing (before networking)

Mechanics & Optics (networked)

Thermal, dielectric, fire

*ESA 7244 DK/tan δ after 1 MHz, the others after 1 kHz — TDS measurement frequencies are not uniform.

6.2 Type Selection — Application Logic

6.3 Inhibitors — critical for Pt addition

All ESA types are Pt-catalyzed and are inhibited (preventing complete curing) by the same classes: sulfur-containing natural and synthetic rubbers (neoprene, latex, SBR), Sn-catalyzed silicones (all CAF types, RTV-2 condensation-curing), amine-catalyzed epoxides, Sn-stabilized PVC, and certain PU elastomers. Separation between Sn and Pt lines in dosing and curing systems is mandatory.

6.4 ESASIL 250

Listed separately in our product range (article code 40-683.KE.K025). Part of the ESA family; TDS available upon request.

7. Bluesil Fluid 47V — silicone oils (PDMS)

The 47V series is Elkem's standard range of linear polydimethylsiloxane oils. The number after "47V" indicates the kinematic viscosity in cSt (mm²/s) at 25 °C — a 47V 100 has 100 cSt, a 47V 12500 has 12,500 cSt. This is not a product code in the traditional sense, but rather an integrated classification system.

7.1 Common characteristics of the 47V series

Values ​​from TDS No. 969-V10 (Elkem, 2024/06/13, series 47V50 to 47V1'000). From 47V 100 onwards, the parameters are independent of viscosity. Exception 47V 50: density 0.959 (instead of 0.965–0.970), flash point 280 °C (instead of 300), refractive index 1.402 (instead of 1.403), dielectric strength 15 kV/mm (instead of 16) — slightly lower values ​​because the chain length distribution is more strongly influenced by the dimer content.

7.2 Which viscosity for which application?

7.3 Table — Bluesil Fluid 47V (12 viscosities)

Values ​​taken directly from TDS n° 969-V10. For the higher viscosities (5,000 to 600,000), Elkem uses the same core values ​​without further differentiation.

7.4 Other silicone oils

8. Pastes — dielectric, thermal, assembly technology

Silicone pastes consist of silicone oil (usually PDMS) and silica filler , supplemented by additives such as metal oxides (for thermal conductivity) or graphite (for conductivity). The silica dispersion makes the material pasty, non-drip, and allows for controllable properties (density, consistency, thermal conductivity). This clearly distinguishes them from silicone grease (→ Chapter 9), which is thickened with lithium soap. Elkem classifies pastes as "compounds" in his official taxonomy.

Bluesil Paste 4 — the classic dielectric protective paste. ρ 1.0, operating temperature −40 to +200 °C. PDMS + inert fillers. Protects contacts against moisture and corrosion, lubricates O-rings, and facilitates the installation of rubber and plastic seals. Essential for switching, starting, and ignition systems.

Bluesil Paste 340 — Thermal paste. ρ 1.8 — significantly higher density thanks to metal oxide filling. Thermal conductivity in the range of 0.7–1.0 W/m·K. For use with heat sinks, thermal sensors, and semiconductor packages.

Bluesil Paste M494 — the heavy metal oxide variant. ρ 2.0 — presumably filled with tungsten or zirconium oxide. Used for radioactive shielding or high-performance heat transfer.

Bluesil Paste 7 / 408 / B431 — Standard dielectrics with ρ 1.0 and an operating range of −40 to +200 °C. They differ in consistency (Paste 7 = thinner, B431 = thicker) and dispensing container size.

Table — Pastes

9. Fats — Silicone oil + thickener

Silicone greases consist of silicone oil (PDMS or methylphenyl) plus lithium soap as a thickener—this is the structural difference compared to paste greases (see Chapter 8, thickened with silica). The soap structure remains stable over a wide temperature range, retains its lubricating properties under dynamic and static loads, and acts as both a sealant and a lubricant. Typical operating range: -60 °C to +300 °C. The NG series (non-gelling) is Elkem's standard family for demanding applications.

Bluesil Grease 33 NG — Universal grease. Operating range −40 °C to +175 °C, dropping point 200 °C. For seal lubrication, plain bearings, valves. Neutral to most elastomers.

Bluesil Grease 55 NG — Low-temperature grease. Operating range −65 °C to +175 °C, dropping point 220 °C. Critical for aircraft, automotive, and high-altitude applications. The better choice when the operating environment can drop below −40 °C.

Bluesil TAP Grease — Fittings and valve grease. Food-grade (NSF-H1 similar — specifically test with TDS). Use in breweries, beverage industry, biotechnology.

Bluesil Vacuum Grease — High-vacuum grease. Low vapor pressure, thermally stable. For rotary vane pumps, rotary seals, and vacuum ground joints.

Bluesil Silicone Grease V-761F — Industrial grease. Bulk pack (18 kg), for the maintenance of larger systems.

Table — Fats

10. Silbione Medical — regulated silicones

Silbione is Elkem's umbrella brand for silicones in regulated industries: medical technology, pharmaceuticals, skin contact, wound care, and aesthetic prostheses. The difference to the corresponding Bluesil product doesn't necessarily lie in the chemistry—it lies in:

1. Documentation. ISO 10993 (Biocompatibility), USP Class VI, FDA Compliance, Drug Master File, ISO 13485 Production.
2. Traceability. Batch tracking, change control, GMP production.
3. Quality assurance. Testing for heavy metals, extractable components, and endotoxin load.

The additional costs for Silbione are not marketing costs — they are documentation costs incurred with every medical approval.

10.1 The most important silbione types

Silbione RTV 4410 QC / 4411 A+B — Special effects and prosthetics standard. Shore A 11–15, very soft, 1:1 mix, pot life 20–60 min, cures at room temperature. Applications: Film mask construction, prosthetic liners (leg prostheses, hand prostheses), soft orthopedic insoles. QC = Quick-Cure variant.

Silbione RTV 4420 A+B — medium-hard medical casting material. Shore A 20, η 4,000 mPa·s, pot life 50 min. For medium-hard medical devices — bite splints, dental and mouthguard prototypes, therapeutic soft parts.

Silbione RTV 4320 — fast impression material. Shore A 20, pot life 2 min. Extremely short working time — designed for dental impressions, surgical templates, and rapid prototyping in the clinic.

Silbione Paste 70428 — biocompatible paste. For use in syringe coating and sliding medical devices. ISO 10993.

Silbione Emulsion 70001 — biocompatible aqueous emulsion. Use: Textile and plaster coating for skin contact.

Silbione Resin 76405 — pharmaceutical-grade silicone resin. Presumably MQ resin with certified purity. Tackifier and barrier component for transdermal patches.

Silbione DM 300 GMP — GMP-quality silicone oil. 300 cSt PDMS, pharmaceutically documented.

10.2 Silbione dispersions (1K/CAF)

SILBIONE CAF 72589 / Dispersion CAF 70004 / 71528. Shore A 15 to 60 depending on the variant. Designates one-component, moisture-curing silicone dispersions in solvents — used as a low-viscosity coating for transdermal patches, electrodes, wound dressings, and textiles. After solvent evaporation, a biocompatible silicone film forms.

10.3 Silbione Oils

Table 10.4 — Silbione Medical (11 products)

10.5 Mechanical characteristics of the Silbione RTV systems

Relevant for prosthetic, film mask and soft tissue applications — soft Shore A values ​​combined with high elongation and tensile strength.

Notably, Silbione 4411 has an elongation at break of 1,000% — this is the range for highly elastic prosthetic liners that must withstand repeated body stretching over years. 4420 combines higher strength (5 MPa) with still good elongation (650%) — for mechanically more stressed components such as bite splints or therapeutic soft parts.

For Silbione-CAF dispersions, the following mechanical properties apply: CAF 72589 (Shore 15, 0.6 MPa / 220%), Dispersion 70004 (Shore 30, 3 MPa / 250%), Dispersion 71528 (Shore 60, 5 MPa / 150%) — each after solvent evaporation and complete curing.

Table — Silbione 1K/CAF (3 products)

Table — Silbione Oils (3 products)

11. Catalysts — the engine of networking

RTV-2 chemistry only works with the correct catalyst. During condensation , the catalyst controls pot life, curing, and final properties.

12. Additives, inhibitors, primers, thinners

These additives modify rheology, pot life or adhesion — they are useless without a base system, but indispensable in the right context.

Bluesil ADD 11013 — Addition crosslinking additive. Function according to nomenclature: possibly pot life extender or adhesion improver for Pt systems.

Bluesil Additive PC Thixo — Thixotropic Agent. Makes a liquid RTV-2 pseudoplastic — flows when mixed/applied, remains stable when at rest. For vertical application and dam-and-fill castings.

Bluesil Inhibitor 3 — Platinum catalysis inhibitor. Extends the pot life of platinum systems in a controlled manner. Dosage in the ppm range. Type: probably 1-ethinylcyclohexanol or similar.

Bluesil Primer 131 / PM 811 A+B / PM 820 / PBM 821 — Adhesion promoters. Applied to the substrate before potting/bonding to ensure silicone adhesion to metals, glass, and plastics. Without a primer, the silicone will slip off after a few temperature cycles.

Bluesil SP 3300 — Special component. Listed as "Other" in Odoo — clarify specific function from TDS.

Bluesil-Diluant 2030 — Silicone thinner. For thinning dispersions or cleaning tools. ρ 0.87 indicates a light solvent (siloxane oligomer or isoparaffin).

13. Resins — Silicone resins for coatings

Silicone resins are low-molecular-weight, three-dimensionally branched siloxane polymers —unlike linear oils (Chapter 7). Their structure is described by four building blocks, named according to the number of oxygen bonds per silicon atom:

• M = O₁/₂Si(CH₃)₃ (monofunctional, chain end)
• D = O₂/₂Si(CH₃)₂ (difunctional, linear unit)
• T = O₃/₂Si(CH₃) (trifunctional, branching)
• Q = O₄/₂Si (quadrifunctional, network node)

Practically relevant combinations include MQ (chain ends + network nodes, typically used as tackifiers), MDT, MDQ , and methyl and methylphenyl variants. Phenyl groups increase temperature and UV resistance as well as compatibility with organic compounds.

Networking takes place via three reactive groups:

• Hydroxy (-OH) — Condensation at room temperature, catalyst-dependent (most common type).
• Alkoxy (-OR) — hydrolyzes to hydroxy at atmospheric humidity; more stable for storage.
• Vinyl (-CH=CH₂) — Addition reaction with Pt (as in RTV) or peroxide (as in HCR).

Silicone resins are supplied dissolved, emulsified, or diluted in silicone polymers. After curing, they form thermally highly stable layers—permanently resistant up to 250 °C, and briefly up to 500 °C. They are used in high-temperature coatings (exhaust coatings, ovens, engine paints), as tackifiers for silicone rubbers, as adhesion promoters in PPE adhesives, as release agent components, and for water repellency on building and textile substrates.

14. Emulsions — Silicone in water

Bluesil EMUL E1P — Standard silicone emulsion. Aqueous silicone emulsion for textile finishing, glass release agent and paper finishing.

Bluesil Microemul PEX 21860 — Microemulsion. Extremely small droplet size (< 100 nm), appearing transparent. Used in cosmetics, gloss enhancers, and high-quality release agents.

15. Silcolapse — Defoamer

The Silcolapseseries is Elkem's family of industrial defoamers. In Elkem's taxonomy, it is listed under "Compounds": PDMS + hydrophobic silica particles, active content usually 100%, viscosities between 100 and 1,000,000 cSt. The mechanism of action is surface displacement: The oil/silica droplets reach the liquid-air interface, spread out there (low surface tension of the PDMS), and the silica particles mechanically destabilize the foam layer—the bubble bursts.

Practical dosage: 1–100 mg/kg (0.0001–0.01 wt% in the process medium). The extremely low dosage compared to organic defoamers is the key economic advantage—plus chemical inertness, heat and pH stability. Applications include textile finishing, the paper industry, wastewater treatment, plastics recycling (PET/HDPE washing processes), and chemical, fermentation, and digestion processes.

Data gap in Odoo. The Silcolapse line currently has no technical data listed in our catalog and no linked TDS. For specific projects, please obtain the Elkem TDS – it documents the active ingredient, pH, viscosity, compatibility, and dosage.

16. Selection guide — which product for which application?

The following matrix is ​​a first heuristic, not a definitive answer. It covers the most common SILITECH projects.

16.1 Mold making — Castings from synthetic resin, plaster, wax, candles

16.2 Electronic potting and dielectrics

16.3 Sealing and bonding (1K from cartridge)

16.4 Lubrication, Separation, Maintenance

16.5 Medical technology, skin contact, pharmaceuticals

16.6 Defoaming

17. Common Mistakes and Pitfalls

17.1 Potting time misjudged

Pot life is not the same as demolding time. Pot life is the point at which the mixed material no longer flows smoothly— no more pouringonward. Curing time is 5 to 20 times longer. Planning based on pot life instead of curing time regularly leads to partially used batches.

17.2 Platinum catalysis poisons

In addition-RTV-2, even trace amounts of the following substances lead to inhibition:

• Sulfur (latex gloves, vulcanized rubber pads)
• Amines (some paints, adhesive tapes, hardeners for epoxies)
• Tin (tin soaps in plastic stabilizers, condensation RTV residues on tools)
• Copper and copper salts
• Some polyester catalysts

Practical advice: Clean tools, containers, and stirrers thoroughly before each attempt. If in doubt: conduct a small test run; if inhibition occurs, clean the substrate or switch to condensation.

17.3 Catalyst dosage too aggressive

The assumption that "more catalyst = faster" only holds true at the lower end of the scale. Beyond the manufacturer's recommendation, the elastomer becomes brittle, and its elongation at break and tensile strength deteriorate. Dosage should be based on the TDS (Total Dissolved Solids) dosage, not on intuition.

17.4 Mold lifespan overestimated

One RTV-3325 mold produces 50–200 casts depending on the medium:

• Polyester resin with aggressive styrene monomer → approx. 30–50 castings
• Epoxy (prepared with CATA SPE) → 100–150 casts
• Plaster, wax, low-temperature metals (tin) → up to 200 casts

Storage: cool (< 25 °C), dark, flat. Re-grease with silicone spray or Bluesil 47V 1000 every 10–20 castings.

17.5 Acetic acid CAF on electronics

A classic. Acetic acid-curing CAF types (typical household sanitary silicones) attack copper and silver over time. For electronics, use only neutral CAF (alkoxy- or oxime-curing). If in doubt, check the Bluesil product number against the TDS.

Confusing 17.6 TDS versions

Elkem updates TDS regularly. Our Odoo system may contain older versions. For precise interpretation of new developments: Request TDS directly from Elkem or SILITECH and work with the most up-to-date document.

Deriving 17.7 Shore A from the product number

This does not work with CAF (CAF 4 ≠ Shore A 4), not with Bluesil RTV (3325 ≠ Shore A 33), and not with Silbione. The product number is internal to Rhodia/Elkem and follows historical coding conventions, not a logic based on a specific characteristic value.

18. Frequently Asked Questions

What are the differences between Rhodorsil, Bluestar Silicones, Elkem Silicones and Bluesil?

These are four names for the same product line across four company eras. Rhodorsil is the original name from the Rhodia era, Bluestar Silicones the interim brand from 2007 to 2018, Elkem Silicones from 2018 onwards, and since mid-2026, the majority of the division has reverted to Bluestar. Product-wise, everything is currently marketed under Bluesil / Silbione / Silcolapse —the product brands are not affected by the ownership change in 2026 in the short term. If you still know a product as "Rhodorsil RTV" or "Bluestar RTV," the current equivalent is the Bluesil product of the same name.

What does the change of ownership in 2026 mean for my deliveries?

Nothing in the short term. The European upstream plant in Roussillon (FR) will remain with Elkem ASA and continue to supply the downstream plants, which are being transferred to Bluestar, under a 5-year contract. Formulations, article numbers, specifications, and the supply chain will remain identical. In the medium term, new MSDS and certificates may be issued with Bluestar as the issuer, and brand adjustments may be necessary. See section 1.2 for a complete overview.

What does CAF mean?

Cold-curing silicone elastomer (CAF) is a historically French term from the Rhodia era. It refers to one-component, moisture-curing sealants and elastomers. The number following CAF is a product number, not a Shore hardness rating.

Condensation or addition?

Condensation (Sn catalysis): robust against contamination, but shrinks 0.3–0.8%, limited mold life. Addition (Pt catalysis): shrinks < 0.1%, dimensionally stable, but sensitive to S, N, Sn, amines, copper. For precision, always use addition; for robustness/synthetic resin, use condensation.

Which silicone oil can be used as a release agent?

For standard injection molding: Bluesil Fluid 47 V 350. For spray applications: 47 V 50 to 100. For thicker release films: 47 V 1000.

How long does an RTV-3325 mold last?

50–200 casts, depending on the casting medium. Polyester resin is the most aggressive (~50 casts), plaster and wax are gentler (up to 200). Between casts, lubricate with silicone spray, store in a dark and cool place, flat or in the original support mold.

Bluesil RTV 3325 with epoxy — is that possible?

Yes, but only with SPU catalyst. Standard CATA-24H degrades faster upon contact with epoxy, halving or reducing the mold lifespan by a third.

Do I need a primer?

For bonding to glass, metal, and untreated plastics: yes. Without a primer, the silicone can detach after a few temperature cycles. Silicone-to-silicone or silicone-to-untreated foams often bonds well without a primer.

Silbione or Bluesil — when do I need Silbione?

If you are manufacturing a medical device (ISO 13485 production, CE mark), if the product is certified to have skin contact or be implanted, or if your quality management system requires raw materials documented in a Drug Master File. For all other applications, Silbione is usually overkill—Bluesil is sufficient.

Can I use Silcolapse 5020 in food?

No. Silcolapse 5020 has industrial approval, but not explicit food contact approval. For food contact, choose the Silcolapse 7140 (40% active, food contact approval) — request TDS and current regulatory information from SILITECH.

I need something that isn't listed here.

The SILITECH range includes the 155 Elkem products we carry; the complete Elkem catalog is larger. Custom orders are possible. For specific requirements (hardness, temperature, regulatory compliance), please contact SILITECH directly—we will clarify available alternatives from the extended Elkem portfolio.

19. Sources and further documentation

Primary sources (Elkem Silicones):

• Elkem Silicones: Bluesil product line
• Elkem Silicones: CAF series
• Elkem Silicones: Silbione — Silicones for human health
• Elkem Silicones: Silcolapse Foam Control Agents

Referenced Technical Data Sheets:

• Bluesil RTV 3325 TDS (Elkem, current version)
• Bluesil ESA 7250 A&B TDS n° 542-V2 (2020/01/13)
• CAF 530 TDS n° 1896-V11 (2023/09/26)
• CAF 4 TDS n° 746-V1 (2018/08/22)
• Bluesil RTV 3040 TDS n° 2859-V5 (2021/08/02)

Transaction Elkem → Bluestar (2026):

• Elkem ASA: Strategic project announcement — Elkem to sell majority of Silicones division to Bluestar (press release, February 13, 2026)
  Elkem Strategic project announcement PDF
• Elkem ASA: Strategic divestment for profitable growth — Selling majority of Silicones division to Bluestar (Investor Presentation, February 13, 2026)
  Elkem Investor Presentation Bluestar PDF
• Elkem ASA: Minutes from Extraordinary General Meeting (Minutes EGM, March 9, 2026)
  Minutes from Extraordinary General Meeting PDF

Technical reference literature:

• Elkem Silicones: Silicone School — Material Science Inside (Ebook, 2025). Official technical introduction to silicone chemistry, elastomers (HCR/LSR/RTV-1/RTV-2) and fluids (oils/emulsions/resins/grease/paste/compounds).
  Elkem Silicone School PDF

Further information at SILITECH:

• Biocompatible silicones: ISO 10993 and USP Class VI
• Silicone oil viscosity guide
• Mold Making Basics: Condensation vs. Addition

Update notice: This article will be reviewed and updated after the closing of the Elkem-Bluestar transaction (expected at the end of April/beginning of May 2026) as soon as concrete information on brand policy, company name and document issuance under the new owner is available.