Elkem Silicones — An Overview of the Complete Product Range | SILITECH

Bluesil, Silbione, Silcolapse —three brands, one manufacturer. This guide explains how the product range is actually organized, which product is designed for which application, and where the differences really matter 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 transaction on March 9, 2026; the transaction is expected to close in late April/early 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. Manufacturers and Brand Logic — As of 2026

The manufacturer behind Bluesil, Silbione, and Silcolapse is one of four fully integrated silicone producers worldwide (alongside Dow, Wacker, and Shin-Etsu)—with plants in Roussillon (France), York (U.S.), Jiangxi (China), Chakan (India), and other locations.

1.1 Historical sequence of names

This same product line has had four names throughout its industrial history:

Rhodorsil, Bluestar Silicones, and Elkem Silicones refer to the same product lines across different periods in the companies' histories. If you are familiar with a product under the name "Rhodorsil RTV" or "Bluestar RTV," its current counterpart is the Bluesil product of the same name.

1.2 Change of Ownership in 2026 — What Customers Need to Know

Closing in late April/early May 2026. From the customer’s perspective , this is a change in ownership, not a change in product: the facilities, recipes, and formulations will remain the same. Short-term effects and risks for SILITECH customers:

1.3 Current Brand Logic

Rule of thumb. The brand name reflects the application, not the chemical composition. A Silbione RTV and a Bluesil RTV can be nearly identical chemically—the difference lies in documentation, regulatory compliance, and quality control. If you’re not manufacturing medical devices, you’re usually paying for documentation from Silbione that you’ll never need. If you are manufacturing medical devices, you’re not allowed to use Bluesil.

2. The product range in 18 product groups

2.1 Elkem's official product taxonomy ↔ SILITECH product range

Elkem Silicones 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:

Not included in Elkem’s main categories, but part of the SILITECH product range: Catalysts (6), Additives/Inhibitors/Primers/Dilutants (10), Silcolapse defoamers (5) — see Chapters 11, 12, and 15.

2.2 18 practical product groups (SILITECH classification)

Of the 155 products currently offered by SILITECH AG, 18 distinct groups have been identified for this reference work. These groups provide a more detailed breakdown of the Elkem taxonomy—for example, "RTV-2" is divided into Mold Making / Electronics Encapsulation / Medical, because the applications and selection criteria differ in each of these areas:

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

RTV-2 stands for Room Temperature Vulcanizing, Two Component: two components that cross-link into an elastomer at room temperature after mixing. Two fundamental chemical systems compete, and the choice between them influences material selection and the process more than any other parameter.

3.1 Condensation vs. Addition — The Key Difference

Let's be honest. From a technical standpoint, addition is almost always the cleaner solution—unless the application requires robust bonding to resist contamination, or the cost of a platinum system is prohibitive. Condensation-curing RTV-2 sealants aren't "worse"; they're more forgiving —which is the deciding factor in many real-world workshops.

3.2 The Main Product Families in Detail

Bluesil RTV 141 / 147 / 148 — The workhorse trio (addition-curing). These three are often confused, but are intended for different applications.

• RTV 141 — Shore A 50, transparent, viscosity ≈ 4,000 mPa·s, pot life 4 hours, demolding time 36 hours. Clear elastomer for applications requiring visibility through the material (light guides, optical prototypes, diaphragm seals).
• RTV 147 — Shore A 60, harder, η_A ≈ 150,000 mPa·s (paste-like), pot life 2 hours. 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 hours. Typically combined with RTV 147 B (cross-compounding) to achieve intermediate hardness levels.

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 the industry standard for clear prototype molds and technical inserts.

Bluesil RTV 3325 / 3325P — the classic choice 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 hours at 23 °C using CATA 24H). The industry standard for detailed decorative molds, because its tear strength allows for the demolding of complex undercuts.

The catalyst determines the pot life and curing time:

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

Bluesil RTV 3410 / 3535 / 3720 — Quick-Cure family. Addition cure, pot life 3–15 min, demolding 15–35 min. For mass production with short cycles — such as automated casting. Important: These fast-curing compounds are sensitive to surface contamination; even a trace of sulfur or stannic acid soap will deactivate the platinum catalyst.

Bluesil RTV 3440 / 3445 / 3450 — the medium hardness grade for technical molds. Shore A 40–50, η ≈ 13,000–15,000 mPa·s, variable pot life (60–90 min), demolding 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 a bubble-free finish is critical.

3.3 Overview of Product Families — Bluesil RTV-2 Mold Making

All values are taken from the official Elkem TDS. One row per product family; the variants in the product range (A, B, various colors, and container sizes) share the same chemical and physical properties.

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

3.4 Mechanical Properties — RTV-2 Molding

For the design of mechanically stressed molds and engineering castings.

For the sake of completeness: Electrical parameters (dielectric strength, volume resistivity, tan δ) are critical in electronic potting—see Chapter 6 (ESA) and the relevant TDS.

4. Bluesil RTV-2 Specialty Products (Encapsulation, Dielectrics, High Temperature)

In addition to 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 mass production potting in electronics, where fast cycle times are critical.

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

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

Bluesil-V-695 / V-1062S — specialty electrically insulating elastomers. The V series refers to formulations specifically designed for vulcanization; these often feature barrier properties for cable and coil encapsulation.

Table — Bluesil RTV-2: More (19 products)

5. CAF Series — Single-component sealing and bonding elastomers

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

Let’s clear up a common misunderstanding. The CAF number does not indicate the Shore hardness. CAF 4 has a Shore A hardness of 37, CAF 33 has a Shore A hardness of 25, and CAF 530 has a Shore A hardness of 34. If you choose based on the number, you’ll often end up with the wrong one. Always select based on the TDS.

5.1 The Most Common Types of CAF in Practice

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

CAF 3 / CAF 30 / CAF 33 — the standard grades. Shore A 20–26. Typically used in expansion joints, glass seals, and plumbing applications (CAF 30 and 33 are available in transparent, white, and black).

CAF 530 — an adhesive and sealant with excellent adhesion to glass, metal, and plastic. Shore A 34, tensile strength 3.5 MPa, elongation at break 450%, tear strength 15 kN/m, max. temperature +150 °C (+185 °C for short periods). Important: CAF 530 is not suitable for continuous high-temperature applications—CAF 33 or CAF 730 are available for that purpose.

CAF 730 MF — the classic high-temperature compound. Shore A 25, Tmax +200 °C (+225 °C for short periods). MF = Medium Flow, but flows under light pressure. Oven door gaskets, exhaust systems, thermal machines.

CAF 99 AXAD — the ultimate choice. Shore A 51, min. temp. −70 °C, max. temp. +250 °C (+300 °C for short periods). AXAD variant for demanding high- and low-temperature applications involving mechanical stress.

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

5.2 Overview of CAF Families

5.3 Mechanical and Curing Properties of the CAF Series

The skin formation time and full cure time of 24 hours are critical during application—they determine the application window and the curing rate per coat at a relative humidity of 50% (23 °C).

Notes: CAF 1 has the highest tensile strength in the standard series, while CAF 530 offers the highest tear resistance and puncture resistance—hence its preference for adhesive applications. CAF 33 is the classic high-elongation grade (500%), suitable for movement joints. CAF 99 AXAD is the most mechanically rigid and thermally resistant (Shore 51, Tmax 250 °C).

6. Bluesil ESA — 2K Pt-cure: Encapsulation, Dielectric, Bonding

The ESA series (Elastomère Silicone Adhésif) is Elkem’s line of products for potting, encapsulation, and adhesive sealing in the electronics and electrical industries. Chemistry: 2-component, platinum-cured 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 rather poured, dispensed, or cast; LSR injection molding is a separate Elkem product line (not included in the SILITECH range).

The five ESA families in the product range cover a wide variety of applications—the specifications are not uniform but vary significantly by type. Key differences:

• ESA 6110 — RT-curing, optically clear silicone gel (no measurable tensile strength). The softest type in the series, 1:1, QC version with a 5-minute pot life.
• ESA 7244 — heat-curing two-component 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), Shore A 50 per ISO R 868.
• ESA 7250 E5 — RT-curing, optically clear, high-strength elastomer (tensile strength 6.2 MPa, elongation 115%), 10:1 mix ratio, suitable for accelerated curing.
• ESA 7252 — RT-curing, black/white, flame-retardant, thermally conductive potting compound (λ 0.42 W/m·K), 1:1 mixing ratio, pot life 1.5 hours, full cure 8 hours at 23 °C.

6.1 Parameters by variant

Processing (before cross-linking)

Mechanics & Optics (Integrated)

Thermal, dielectric, fire

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

6.2 Type Selection — Application Logic

6.3 Inhibitors — Critical for Pt Addition

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

6.4 ESASIL 250

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

7.1 Common Features of the 47V Series

Values from TDS No. 969-V10 (Elkem, June 13, 2024, series 47V50 to 47V1,000). Starting at 47V 100, 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 No. 969-V10. For higher viscosities (5,000 to 600,000), Elkem applies the same core values without further differentiation.

7.4 Other silicone oils

8. Pastes — dielectric, thermal, and assembly-related

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

Bluesil Paste 4 — the classic dielectric protective paste. ρ 1.0, operating temperature range −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 switchgear, starter, and ignition systems.

Bluesil Paste 340 — Thermal interface compound. ρ 1.8 — significantly higher density thanks to metal oxide fillers. Thermal conductivity in the range of 0.7–1.0 W/m·K. Used for heat sinks, temperature 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 radiation shielding or for high-performance heat transfer.

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

Table — Pastes

9. Fats — silicone oil + thickener

Silicone greases consist of silicone oil (PDMS or methylphenyl) combined with lithium soap as a thickener—this is the structural difference from the paste (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 product family for demanding applications.

Bluesil Grease 33 NG — Universal grease. Operating temperature range: −40 °C to +175 °C, dropping point 200 °C. For lubricating seals, plain bearings, and valves. Compatible with most elastomers.

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

Bluesil TAP Grease — Fitting and valve grease. Food-grade (NSF H1-compliant — check the TDS for specific details). Used in breweries, the beverage industry, and biotechnology.

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

Bluesil Silicone Grease V-761F — Industrial grease. Bulk package (18 kg), for maintenance of large-scale equipment.

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 prosthetics. The difference from the corresponding Bluesil product does not necessarily lie in the chemistry—it lies in:

1. Documentation. ISO 10993 (biocompatibility), USP Class VI, FDA compliance, Drug Master File, ISO 13485 manufacturing.
2. Traceability. Batch tracking, change control, GMP production.
3. Quality assurance. Testing for heavy metals, extractable substances, and endotoxin levels.

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

10.1 The Main Types of Silbione

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

Silbione RTV 4420 A+B — medium-hard medical-grade casting compound. Shore A 20, viscosity 4,000 mPa·s, pot life 50 min. For medical devices requiring medium hardness — bite splints, dental mouthguard prototypes, therapeutic soft components.

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 clinical settings.

Silbione Paste 70428 — biocompatible paste. Used for syringe coating and sliding medical devices. ISO 10993.

Silbione Emulsion 70001 — biocompatible aqueous emulsion. Application: Coating for textiles and adhesive bandages intended for skin contact.

Silbione Resin 76405 — pharmaceutical silicone resin. Presumably MQ resin with certified purity. Tackifiers and barrier components for transdermal patches.

Silbione DM 300 GMP — GMP-grade silicone oil. 300 cSt PDMS, pharmaceutical-grade.

10.2 Silbione Dispersions (1K/CAF)

SILBIONE CAF 72589 / Dispersion CAF 70004 / 71528. Shore A 15 to 60 depending on the variant. Refers to single-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 Properties of Silbione RTV Systems

Suitable for prosthetics, film masks, and soft tissue applications—low Shore A hardness combined with high elongation and tensile strength.

Noteworthy: Silbione 4411 has an elongation at break of 1,000%—this places it in the category of highly elastic prosthetic liners that must withstand multiple-fold stretching over many years. 4420 combines higher strength (5 MPa) with still good elongation (650%) — for components subjected to higher mechanical stress, such as bite splints or therapeutic soft parts.

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

Table — Silbione 1K/CAF (3 products)

Table — Silbione Oils (3 products)

11. Catalysts — The Driving Force Behind Networking

RTV-2 chemistry only works with the right catalyst. During curing, the catalyst controls the pot life, curing rate, 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-curing additive. Function according to the nomenclature: possibly a pot life extender or adhesion promoter for Pt systems.

Bluesil Additive PC Thixo — Thixotropic agent. Makes a liquid RTV-2 pseudoplastic—it flows during mixing/application but sets when left undisturbed. For vertical application and dam-and-fill casting.

Bluesil Inhibitor 3 — Platinum catalyst inhibitor. Extends the pot life of platinum-based systems in a controlled manner. Dosage in the ppm range. Type: likely 1-ethynylcyclohexanol or similar.

Bluesil Primer 131 / PM 811 A+B / PM 820 / PBM 821 — Adhesion promoters. These are applied to the substrate prior to potting or bonding to ensure proper adhesion of the silicone to metals, glass, and plastics. Without a primer, the silicone will slipp off after a few temperature cycles.

Bluesil SP 3300 — Special component. Listed as "Other" in Odoo — clarify specific function based on the technical data sheet.

Bluesil-Diluant 2030 — Silicone thinner. For diluting dispersions or cleaning tools. A density of 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 structural units, named according to the number of oxygen bonds per silicon atom:

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

Combinations relevant in practice include MQ (chain ends + network nodes, typically used as tackifiers), MDT, MDQ, and methyl and methyl-phenyl variants. Phenyl groups enhance temperature and UV resistance as well as compatibility with organic materials.

Networking takes place through three discussion groups:

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

Silicone resins are supplied in dissolved, emulsified, or diluted form in silicone polymers. After curing, they form thermally highly stable coatings—capable of withstanding temperatures up to 250 °C continuously and up to 500 °C for short periods. Used in high-temperature coatings (exhaust coatings, ovens, engine coatings), as tackifiers for silicone rubbers, as adhesion promoters in PPE adhesives, as release agent components, and for water repellency in construction and textile substrates.

14. Emulsions — Silicone in Water

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

Bluesil Microemul PEX 21860 — Mikroemulsion. Extrem kleine Tröpfchengrösse (< 100 nm), transparent erscheinend. Einsatz in Kosmetik, Glanzmitteln, hochwertigen Trennmitteln.

15. Silcolapse — Defoamer

The Silcolapse series is Elkem’s line of industrial defoamers. Classified under “Compounds” in Elkem’s taxonomy: PDMS + hydrophobic silica particles, active content typically 100%, viscosities between 100 and 1,000,000 cSt. The mechanism of action is interfacial displacement: The oil/silica droplets reach the liquid-air interface, spread out there (due to the low surface tension of the PDMS), and the silica particles mechanically destabilize the foam lamella—causing the bubble to burst.

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

Data gap in Odoo. The Silcolapse line currently has no technical data or linked TDSs in our catalog. 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 preliminary guide, not a definitive answer. It covers the most common SILITECH projects.

16.1 Mold Making — Castings from synthetic resin, plaster, wax, and candles

16.2 Electronic Encapsulants and Dielectrics

16.3 Sealing and Adhesives (1-component from a cartridge)

16.4 Lubrication, Disassembly, Maintenance

16.5 Medical Technology, Skin Contact, Pharmaceuticals

16.6 Defoaming

17. Common Mistakes and Pitfalls

17.1 Incorrect estimation of pot life

Pot life is not the same as curing time. Pot life is the point at which the mixed material no longer flows freely— do not pour after this point. Curing time is 5 to 20 times longer. Planning based on pot life rather than curing time regularly results in wasted batches.

17.2 Platinum Catalysis Poisoned

In the case of addition-curing RTV-2, even trace amounts of the following substances can cause inhibition:

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

Practical tips. Clean all tools, containers, and stirrers thoroughly before each batch. If in doubt: Prepare a small test batch; if inhibition occurs, clean the substrate or switch to condensation.

17.3 Catalytic converter dosage too aggressive

The assumption that "more catalyst = faster curing" is only true in the lower range. If you exceed the manufacturer's recommendation, the elastomer becomes brittle, and both elongation at break and tensile strength decrease. Follow the dosage instructions in the technical data sheet, not your gut feeling.

17.4 Overestimation of mold life

An RTV-3325 mold can produce 50–200 castings, depending on the material:

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

Lagerung: kühl (< 25 °C), dunkel, flach. Mit Silikonspray oder Bluesil 47V 1000 alle 10–20 Abgüsse nachfetten.

17.5 Acetic Acid CAF on Electronics

Standard. Acetic acid-curing CAF types (typical household sanitary silicones) corrode 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.

17.6 Mixing up TDS versions

Elkem regularly updates its TDS. Some older versions are stored in our Odoo system. For accurate design of new developments: Request the TDS directly from Elkem or SILITECH and use the most up-to-date document.

17.7 Derive the Shore A value from the product number

This does not apply to CAF (CAF 4 ≠ Shore A 4), Bluesil RTV (3325 ≠ Shore A 33), or Silbione. The product number is an internal Rhodia/Elkem code and follows historical coding conventions, not a logic based on physical properties.

18. Frequently Asked Questions

How do Rhodorsil, Bluestar Silicones, Elkem Silicones, and Bluesil differ?

These are four names for the same product line spanning four eras of the company. Rhodorsil is the original name from the Rhodia era, Bluestar Silicones was the interim brand from 2007 to 2018, Elkem Silicones took over in 2018, and since mid-2026, the majority of the division has returned to Bluestar. On the product side, everything is currently marketed under Bluesil / Silbione / Silcolapse —the product brands are not immediately affected by the 2026 change in ownership. If you are familiar with a product still listed as "Rhodorsil RTV" or "Bluestar RTV," its current equivalent is the Bluesil product of the same name.

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

In the short term, nothing. The European upstream plant in Roussillon (FR) will remain with Elkem ASA and will continue to supply the downstream plants, which are being transferred to Bluestar, under a 5-year contract. Formulations, part numbers, specifications, and the supply chain will remain unchanged. Possible in the medium term: newly issued MSDSs and certificates with Bluestar as the issuer, and possibly brand adjustments. See Section 1.2 for a complete overview.

What does CAF stand for?

Cold-curing silicone rubber — silicone elastomer, cold-curing. A historical French term from the Rhodia era. Refers to single-component, moisture-curing sealants and elastomers. The number following CAF is a product number, not a Shore hardness rating.

Condensation or addition?

Kondensation (Sn-Katalyse): robust gegen Kontamination, aber schrumpft 0.3–0.8 %, limitierte Formen-Lebensdauer. Addition (Pt-Katalyse): schrumpft < 0.1 %, dimensionsstabil, aber empfindlich gegen S, N, Sn, Amine, Kupfer. Für Präzision immer Addition, für Robustheit/Kunstharz Kondensation.

Which silicone oil should 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 castings, depending on the casting medium. Polyester resin is the most aggressive (~50 castings), while plaster and wax are gentler (up to 200). Re-lubricate with silicone spray between castings; store in a cool, dark place, either flat or in the original support mold.

Bluesil RTV 3325 with epoxy—is that possible?

Yes, but only with the SPU catalyst. The standard CATA-24H degrades more quickly when it comes into contact with epoxy, which cuts the mold's service life in half or to a third.

Do I need a primer?

When bonding to glass, metal, or untreated plastics: yes. Without a primer, the silicone may peel off after just a few temperature cycles. Silicone-to-silicone or silicone to untreated foam often works well without a primer.

Silbione or Bluesil — when should I use Silbione?

If you manufacture a medical device (ISO 13485 production, CE marking), if the product is certified for skin contact or is intended for implantation, 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 products?

No. Silcolapse 5020 has industrial approval but no explicit food-contact approval. For food contact applications, select the Silcolapse 7140 variant (40% active, food-contact approval)—request the TDS and current regulatory information from SILITECH.

I need something that isn't listed here.

The SILITECH product range includes 155 Elkem products; the full Elkem catalog is more extensive. Special orders are available. For specific requirements (hardness, temperature, regulatory compliance), please contact SILITECH directly—we will identify available alternatives from the expanded Elkem portfolio.

19. Sources and Further Reading

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

Technical Data Sheets Cited:

• Bluesil RTV 3325 TDS (Elkem, current version)
• Bluesil ESA 7250 A&B Technical Data Sheet No. 542-V2 (January 13, 2020)
• CAF 530 TDS No. 1896-V11 (September 26, 2023)
• CAF 4 TDS No. 746-V1 (August 22, 2018)
• Bluesil RTV 3040 TDS No. 2859-V5 (August 2, 2021)

Elkem–Bluestar Transaction (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 of the Extraordinary General Meeting (March 9, 2026)
  Minutes of the 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/greases/pastes/compounds).
  Elkem Silicone School PDF

See also 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 following the closing of the Elkem-Bluestar transaction (expected in late April/early May 2026), as soon as specific information regarding brand policy, company name, and document issuance under the new ownership becomes available.