Elkem silicones: the complete range at a glance

Bluesil, Silbione, Silcolapse: three brands, one manufacturer. This guide explains how the product range is actually organized, which product performs which task, and where the differences become truly relevant in practice. The basis is the 155 products that SILITECH AG stores 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 the majority of its Silicones division to Bluestar (China National Bluestar Group). The General Assembly approved this on March 9, 2026, with completion expected at the end of April / beginning of May 2026. For SILITECH customers: Plants, formulations, and delivery capability remain unchanged (details in Section 1.2). Product names and brand management 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-range silicone producers (alongside Dow, Wacker, and Shin-Etsu), with plants in Roussillon (FR), York (USA), Jiangxi (CN), Chakan (IN), and other locations.

1.1 Historical Name Sequence

The same product line has carried four names throughout industrial history:

Rhodorsil, Bluestar Silicones and Elkem Silicones denote technically the same product lines in different corporate eras. If you 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 2026: what customers need to know

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

1.3 Current brand logic

Practical Rule. The brand indicates the use case , not the chemical nature. A Silbione RTV and a Bluesil RTV can be chemically nearly identical; the difference lies in documentation, regulatory compliance, and quality control. Those who do not build medical devices usually pay for Silbione documentation they never need. Those who do build them must not work with Bluesil.

2. The range in 18 product groups

2.1 Elkem's Official Product Taxonomy ↔ SILITECH Product Range

Elkem Silicones itself classifies 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 Elkem's main categories, but in the SILITECH range: Catalysts (6), Additives/Inhibitors/Primers/Diluents (10), Silcolapse defoamers (5), see Ch. 11, 12, 15.

2.2 18 pragmatic product groups (SILITECH classification)

From the 155 products currently carried by SILITECH AG, 18 distinct groups emerge for this reference work. They map the Elkem taxonomy in finer detail, for example, "RTV-2" is split into mold making / electronics potting / medical, because application and selection logic differ there:

3. Bluesil RTV-2: The Core of Mold Making

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

3.1 Condensation vs. Addition: the decisive difference

Honest assessment. Addition is technically almost always the clean solution, unless the application requires robust curing against contamination, or the cost of a platinum system is not viable. Condensation RTV-2 are not "worse", they are more tolerant, which is the decisive point in many real workshops.

3.2 The Most Important Product Families in Detail

Bluesil RTV 141 / 147 / 148: The Workhorse Trio (addition-cure). These three are often confused, but they 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 one must 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 molds with high requirements for edge stability.
• RTV 148: Shore A 40, softer than 147, η ≈ 10'000 mPa·s, pot life 4 h. It is typically combined with RTV 147 B (cross-compounding) to achieve intermediate hardnesses.

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

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

The catalyst determines pot life and curing:

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

Bluesil RTV 3410 / 3535 / 3720: Quick-Cure family. Addition cure, pot life 3 to 15 min, demolding 15 to 35 min. For series production with short cycles, e.g., automatic casting. Important: The fast-curing types are sensitive to surface contamination; any trace of sulfur or tin soap poisons the platinum catalyst.

Bluesil RTV 3440 / 3445 / 3450: the medium hardness class for technical molds. Shore A 40 to 50, η ≈ 13,000 to 15,000 mPa·s, variable pot life (60 to 90 min), demolding 6 to 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 deeply into undercuts, cures overnight. Ideal for components with complex geometry where bubble-free performance is critical.

3.3 Overview of product families: Bluesil RTV-2 mold making

All values from the official Elkem TDS. One line per product family; the variants in the range (A, B, different colors and pack sizes) share the same chemistry and technical data.

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 characteristics of the respective family.

3.4 Mechanical Properties: RTV-2 Mold Making

For the design of mechanically stressed molds and technical cast parts.

For completeness: The electrical characteristics (dielectric strength, volume resistivity, tan δ) are critical for electronic potting, see Chapter 6 (ESA) and dedicated TDS.

4. Bluesil RTV-2 Specialties (Potting, Dielectric, 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 close relatives of the mold-making series.

Bluesil RTV 3040 / 3041: already covered in Section 3.2.

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

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 short-term. Used near engines, exhaust systems, and furnaces.

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

Table: Bluesil RTV-2 Additional (19 Products)

5. CAF Series: One-Component Sealing and Bonding Elastomers

CAF historically stands for Caoutchouc Silicone à Vulcanisation à Froid (silicone elastomer, cold-curing), the abbreviation originates from the French Rhodia line. All CAF products are one-component, moisture-curing: applied from the cartridge, the material forms a skin within minutes upon contact with air humidity and cures in layers (approx. 2 to 3 mm per 24 h at 23 °C and 50 % RH).

Let's clear up a misunderstanding. The CAF number says nothing about Shore hardness. CAF 4 has Shore A 37, CAF 33 has Shore A 25, CAF 530 has Shore A 34. Choosing by number regularly leads to the wrong product. Always select against the TDS.

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 acetic acid-releasing (acetoxy); insurers in electronic applications scrutinize this specification because acetic acid attacks copper components. For metal and electronic contact, use only neutral CAF (oxime/alkoxy).

CAF 3 / CAF 30 / CAF 33: the soft types. Shore A 20 to 26. Typical use in expansion joints, glass seals, sanitary applications (CAF 30 and 33 available in transparent, white, black).

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

CAF 730 MF: the high-temperature classic. Shore A 25, Tmax +200 °C (+225 °C short-term). MF = Medium Flow, but flows under slight pressure. Oven door seals, exhaust environments, thermal machinery.

CAF 99 AXAD: the extreme. Shore A 51, Tmin −70 °C, Tmax +250 °C (+300 °C short-term). 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 cure (suitable for metal/electronics).

5.2 Overview of CAF Families

5.3 Mechanical and Curing Properties of the CAF Series

Skin formation time and through-cure after 24 h are critical during processing; they determine the application time frame and the layer-by-layer cure rate under ambient humidity (23 °C, 50 % RH).

Notes. CAF 1 has the highest tensile strength in the standard series, CAF 530 has the highest tear resistance and the highest dielectric strength, hence the preference for adhesive applications. CAF 33 is the elongation classic (500%), useful for movement joints. CAF 99 AXAD is the mechanically hardest and thermally most extreme (Shore 51, Tmax 250 °C).

6. Bluesil ESA: 2K-Pt addition: Potting, dielectric, bonding

The ESA series (Elastomère Silicone Adhésif) is Elkem's line for potting, embedding, and adhesive sealing in the electronics and electrical industry. 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 sprayed, but rather cast, dispensed, or potted; LSR injection molding is a separate Elkem line (not carried in the SILITECH range).

The five ESA families in the range cover very different applications, and the values are not uniform, but differ significantly by 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 5 min pot life.
• ESA 7244: heat-curing 2K adhesive elastomer (80 to 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 6.2 MPa, Elongation 115 %), Ratio 10:1, accelerable.
• ESA 7252: RT-curing, black/white flame-retardant, thermally conductive potting compound (λ 0.42 W/m·K), ratio 1:1, pot life 1.5 h, through-cure 8 h @ 23 °C.

6.1 Per-Variant Characteristics

Processing (before curing)

Mechanics & Optics (crosslinked)

Thermal, dielectric, fire

*ESA 7244 DK/tan δ at 1 MHz, the others at 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 by the same classes (preventing complete cure): 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 dispensing and curing equipment is mandatory.

6.4 ESASIL 250

Listed separately in the range (item code 40-683.KE.K025). Assigned to the ESA family; TDS available on 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 classical sense, but an integrated classification system.

7.1 Common properties of the 47V series

Values from TDS n° 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 to 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 the 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, assembly

Silicone pastes are silicone oil (usually PDMS) + silica filler: supplemented by additives such as metal oxides (thermal conductivity) or graphite (conductivity). The silica dispersion makes the material pasty, non-dripping, and property-controllable (density, consistency, thermal conductivity). This clearly distinguishes them from silicone grease (→ Chap. 9), which is thickened with lithium soap. Elkem groups 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, facilitates the assembly of rubber and plastic seals. Important for switchgear, starter, and ignition systems.

Bluesil Paste 340: Thermal conductive paste. ρ 1.8, significantly higher density due to metal oxide filler. Thermal conductivity in the range of 0.7 to 1.0 W/m·K. Used for heat sinks, thermal sensors, semiconductor housings.

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 ρ 1.0 and operating range −40 to +200 °C. They differ in consistency (Paste 7 = thinner, B431 = firmer) and package size.

Table: Pastes

9. Greases: Silicone Oil + Thickener

Silicone greases are silicone oil (PDMS or methyl-phenyl) + lithium soap as thickener, which is the structural difference from paste (Chap. 8, thickened with silica). The soap structure remains stable over wide temperature ranges, retains lubricating properties under dynamic and static load, and acts as both sealant and lubricant. Typical application 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, drop 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 location can fall below −40 °C.

Bluesil TAP Grease: Valve and fitting grease. Food-grade approval (similar to NSF-H1, verify with the TDS). Used in breweries, beverage industry, and biotech.

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

Bluesil Silicone Grease V-761F: industrial grease. Bulk packaging (18 kg), for maintenance of larger systems.

Table: Greases

10. Silbione Medical: regulated silicones

Silbione is Elkem's umbrella brand for silicones in regulated industries: medical technology, pharmaceuticals, skin contact, wound care, aesthetic prosthetics. The difference from the corresponding Bluesil product is not necessarily in the chemistry, but 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 cost of Silbione is not marketing; it is documentation cost that is 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 to 15, very soft, 1:1 mix, pot life 20 to 60 min, curing at room temperature. Applications: film mask fabrication, prosthetic liners (leg prostheses, hand prostheses), soft orthopedic insoles. QC = Quick-Cure variant.

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

Silbione RTV 4320: fast impression. Shore A 20, pot life 2 min. Extremely short working time, intended for dental impressions, surgical templates, and rapid prototyping in clinical settings.

Silbione Paste 70428: biocompatible paste. Used in syringe coating, lubricious medical devices. ISO 10993.

Silbione Emulsion 70001: biocompatible aqueous emulsion. Use: textile and dressing coating for skin contact.

Silbione Resin 76405: pharmaceutical silicone resin. Presumably an MQ resin with certified purity. Tackifier and barrier components for transdermal patches.

Silbione DM 300 GMP: Silicone oil in GMP quality. 300 cSt PDMS, pharma-documented.

10.2 Silbione Dispersions (1K/CAF)

SILBIONE CAF 72589 / Dispersion CAF 70004 / 71528. Shore A 15 to 60 depending on the variant. These are 1-component, moisture-curing silicone dispersions in solvents, used as low-viscosity coatings for transdermal patches, electrodes, wound dressings, and textiles. After solvent evaporation, a biocompatible silicone film forms.

10.3 Silbione oils

10.4 Table: Silbione Medical (11 products)

10.5 Mechanical Properties of Silbione RTV Systems

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

Notable: Silbione 4411 with an elongation at break of 1,000%, which is the range of highly elastic prosthetic liners that must withstand repeated body movement 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 mechanical properties are: 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 crosslinking

The RTV-2 chemistry only works with the right catalyst. In condensation , the catalyst controls pot life, cure, and final properties.

12. Additives, Inhibitors, Primers, Thinners

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

Bluesil ADD 11013: addition-cure additive. Function according to nomenclature: possibly a pot life extender or adhesion promoter for Pt systems.

Bluesil Additive PC Thixo: Thixotropic agent. Makes a liquid RTV-2 pseudoplastic, flows during mixing/application, and remains at rest. For vertical application and dam-and-fill potting.

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

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

Bluesil SP 3300: Special component. Listed as "Other" in Odoo; specific function to be clarified from the 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 the linear oils (Ch. 7). The 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)

In practice, relevant combinations are MQ (chain ends + network nodes, typically as tackifier), MDT, MDQ as well as methyl and methyl-phenyl variants. Phenyl groups increase temperature and UV resistance as well as compatibility with organics.

Crosslinking occurs via three reactive groups:

• Hydroxy (-OH): condensation at room temperature, catalyst-dependent (most common type).
• Alkoxy (-OR): hydrolyzes to hydroxy in the presence of air moisture; more storage-stable.
• 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 loadable up to 250 °C, and briefly up to 500 °C. Used in high-temperature paints (exhaust coatings, ovens, engine enamels), as tackifiers for silicone rubbers, as adhesion promoters in PSA adhesives, as a release agent component, and for water repellency of 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: microemulsion. Extremely small droplet size (< 100 nm), appearing transparent. Used in cosmetics, gloss agents, and high-quality release agents.

15. Silcolapse: Defoamers

The Silcolapse series is Elkem's industrial defoamer family. In Elkem's taxonomy, it is classified under "Compounds": PDMS + hydrophobic silica particles, with active content typically 100%, and 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 there (due to the low surface tension of PDMS), and the silica particles mechanically destabilize the foam lamella, causing the bubble to burst.

Practical dosage: 1 to 100 mg/kg (0.0001 to 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. Used in textile finishing, paper industry, wastewater treatment, plastics recycling (PET/HDPE washing processes), chemical, brewing and fermentation processes.

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

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 Electronics potting and dielectrics

16.3 Sealing and Bonding (1K from Cartridge)

16.4 Lubricating, Releasing, Maintaining

16.5 Medical technology, skin contact, pharmaceuticals

16.6 Defoaming

17. Common Errors and Pitfalls

17.1 Pot life misjudged

Pot life is not the same as demolding time. Pot life is the point at which the mixed material no longer flows easily; after this point, do not pour. Cure time is 5 to 20 times longer. Planning with pot life instead of cure time regularly leads to partially used batches.

17.2 Platinum catalysis poisoned

In addition-cure RTV-2, even traces of the following substances lead to inhibition:

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

Practice. Clean tools, containers, and stirrers thoroughly before each batch. When in doubt, make a small test batch; if inhibition occurs, clean the substrate or switch to condensation curing.

17.3 Catalyst dosage too aggressive

The reflex "more catalyst = faster" only holds true in the lower range. Above the manufacturer's recommendation, the elastomer becomes brittle, and tear elongation and tear strength drop off. Dosage according to TDS, not by gut feeling.

17.4 Mold service life overestimated

An RTV-3325 mold achieves 50 to 200 casts depending on the medium:

• Polyester resin with aggressive styrene monomer → approx. 30 to 50 casts
• Epoxy (prepared with CATA SPE) → 100 to 150 pours
• 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 to 20 pours.

17.5 Acetic acid CAF on electronics

Classic. Acetic acid-curing CAF types (typical household sanitary silicones) attack copper and silver in the long term. For electronics, only neutral CAF (alkoxy- or oxime-curing). When in doubt, check the Bluesil product number against the TDS.

17.6 Confusing TDS versions

Elkem regularly updates the TDS. In our Odoo, some older versions are stored. For precise design of new developments: request the TDS directly from Elkem or SILITECH and work with the current document.

17.7 Deriving 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 code conventions, not a property-based logic.

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 corporate eras. Rhodorsil is the original name from the Rhodia period, Bluestar Silicones the interim brand from 2007 to 2018, Elkem Silicones from 2018, and since mid-2026, the majority of the division has returned to Bluestar. On the product side, everything now runs under Bluesil / Silbione / Silcolapse: the product brands are not affected in the short term by the 2026 ownership change. If you know a product as "Rhodorsil RTV" or "Bluestar RTV," the current equivalent is the Bluesil product of the same name.

What does the 2026 ownership change mean for my deliveries?

Nothing in the short term. The European upstream plant Roussillon (FR) remains with Elkem ASA and will continue to supply the downstream plants that are being transferred to Bluestar under a 5-year contract. Formulations, article numbers, specifications, and supply chain remain identical. Possible in the medium term: Newly issued MSDS and certificates with Bluestar as issuer, possibly brand adjustments. See Section 1.2 for the complete overview.

What does CAF mean?

Caoutchouc Silicone à Vulcanisation à Froid, silicone elastomer, cold-curing. Historically French from the Rhodia era. Refers to the 1-component, moisture-curing sealants and elastomers. The number after CAF is a product number, not a Shore hardness value.

Condensation or addition?

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

Which silicone oil as a release agent?

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

Bluesil RTV 3325 with epoxy: is that possible?

Yes, but only with Catalyseur SPU. The standard CATA-24H degrades faster upon epoxy contact, which halves or thirds the mold lifespan.

Do I need a primer?

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

Silbione or Bluesil: when do I need Silbione?

If you manufacture a medical device (ISO 13485 production, CE mark), if the product has certified skin contact or is implanted, or if your QM system requires Drug Master File-documented raw materials. For all other applications, Silbione is usually overkill; Bluesil is sufficient.

Can I use Silcolapse 5020 in food products?

No. Silcolapse 5020 has an industrial approval, but no explicit food approval. For food contact, choose the variant Silcolapse 7140 (40% active, food contact approval); request the TDS and current regulations from SILITECH.

I need something that is not listed here.

The SILITECH range includes the 155 Elkem products we carry; the complete Elkem catalog is larger. Special orders are possible. For specific requirements (hardness, temperature, regulatory compliance), please contact SILITECH directly; we will identify 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 No. 1896-V11 (2023/09/26)
• CAF 4 TDS No. 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, 13.02.2026)
  Elkem Strategic project announcement PDF
• Elkem ASA: Strategic divestment for profitable growth, Selling majority of Silicones division to Bluestar (Investor Presentation, 13.02.2026)
  Elkem Investor Presentation Bluestar PDF
• Elkem ASA: Minutes from Extraordinary General Meeting (EGM Minutes, 09.03.2026)
  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/greases/pastes/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 note. This article will be reviewed and adjusted after the closing of the Elkem-Bluestar transaction (expected 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.