What are casting compounds?
Potting compounds are liquid or paste-like materials that completely encapsulate electronic assemblies and provide permanent protection once cured. Unlike conformal coatings, which form only a thin protective layer of 25 to 75 micrometers, potting compounds fill the entire cavity around the electronics. The result is solid, long-lasting protection against moisture, vibrations, chemicals, temperature fluctuations, and mechanical stress.
Encapsulants prevent corrosion and electrochemical migration caused by moisture, increase creep current resistance between adjacent conductors, secure components against vibration and shock, dissipate heat effectively in thermally conductive variants, and protect against chemical influences such as oils, fuels, and cleaning agents. In safety-critical applications, they also serve as tamper protection, as encapsulated assemblies cannot be opened without causing damage.
Full encapsulation or selective encapsulation?
Before the material issue is resolved, a fundamental decision must be made: Will the assembly be fully encapsulated (potting) or only selectively coated (encapsulation)?
Potting (full encapsulation)
All electronic components are fully encapsulated in a housing with potting compound. Maximum IP protection (up to IP68/IP69K), uniform heat dissipation, secure mounting, and tamper resistance.
Disadvantages: Higher material consumption, added weight, and, in the case of epoxy, cannot be repaired.
Encapsulation (selective)
Critical areas are selectively coated, while connectors and test points remain accessible. This saves material and weight and allows for component replacement.
Disadvantages: IP protection is limited to IP54–IP67; uncoated areas remain vulnerable.
Rule of thumb: IP68/IP69K required → potting. Repairability required → encapsulation. Power dissipation over 5 W → potting with thermally conductive compound. Weight is a critical factor → encapsulation.
A Comparison of the Three Material Classes
Silicone casting compounds
Silicones are the most versatile class of materials for electronics potting. They remain elastic over an extremely wide temperature range (−60 °C to +200 °C; special grades up to +300 °C). Their low mechanical stress protects sensitive components and solder joints. For LED applications, silicones are often the only sensible choice: Special optical formulations are transparent, do not yellow, and have a suitable refractive index.
Typical applications: LED modules, automotive control units, outdoor electronics, solar inverters, sensor technology, medical electronics, aerospace.
Epoxy casting compounds
Epoxy resins offer the highest mechanical strength (Shore D 70–90), excellent adhesion to metals and ceramics, and the highest dielectric strength (up to 25 kV/mm). The main drawback: virtually irreparable after curing, brittleness during temperature changes, and a narrow temperature range (−40 to +130 °C).
Typical applications: high-voltage power supplies, transformers, ignition electronics, underwater electronics, tamper protection.
Polyurethane casting compounds (PU)
PU falls between epoxy and silicone: a balanced set of properties at the lowest cost. Shore hardness can be adjusted (Shore A 60 to Shore D 50), good abrasion resistance. Main drawbacks: hygroscopic, UV-sensitive, very narrow temperature range (−40 to +120 °C).
Typical applications: Industrial control systems, switching power supplies (indoor), e-mobility chargers, BMS modules, building automation.
Material Comparison: Silicone vs. Epoxy vs. Polyurethane
Rating on a scale of 1–10. Higher = better.
Comparison Table
| property | silicone | epoxy | polyurethane |
|---|---|---|---|
| temperature range | −60 to +200 °C (up to +300) | −40 to +130 °C (up to +150) | −40 to +120 °C |
| Shore hardness | Shore A 15–60 | Shore D 70–90 | Shore A 60 – Shore D 50 |
| Dielectric strength | 15–21 kV/mm | 20–25 kV/mm | 16–22 kV/mm |
| λ (default) | 0.16–0.20 W/(m·K) | 0.2–0.3 W/(m·K) | 0.2–0.3 W/(m·K) |
| λ (filled) | 0.30–0.42 W/(m·K) | up to 5 W/(m·K) | up to 1.5 W/(m·K) |
| chemical resistance | very good | awarded | good |
| UV resistance | awarded | good | moderate |
| repairability | good | very difficult | possible |
| price level | high | medium to high | low to medium |
Thermally conductive encapsulants: The λ value is the deciding factor
Modern electronics operate in increasingly compact spaces with ever-higher power densities. Standard encapsulants tend to act as thermal insulators (0.16–0.20 W/(m·K))—they protect the electronics but at the same time trap heat within the component.
Rule of thumb: In many cases, an increase in operating temperature of 10 K can roughly halve the service life of electronic components.
The λ-value (thermal conductivity, W/(m·K)) describes how well a material conducts heat. Still air: 0.025 — unfilled silicones: 0.16–0.20 — filled silicones: 0.30–0.42 — hybrid systems: up to 1.05 — aluminum: 237.
Thermal conductivity is increased by adding mineral or ceramic fillers: aluminum oxide (Al₂O₃), boron nitride (BN), or silicon carbide (SiC). The higher the filler content, the better the thermal conductivity—but also the higher the viscosity.
Thermal conductivity of all SILITECH encapsulation products
λ values from the manufacturer's TDS. Higher value = better heat dissipation.
When is thermally conductive potting worthwhile? From approximately 1 W of power dissipation per cm² of component surface area. For standard sensors: 0.16–0.20 W/(m·K). For power electronics: 0.30–0.50 W/(m·K). For critical thermal management with fire protection: Permabond MT3836 with 1.05 W/(m·K) and UL 94 V-0.
SILITECH Encapsulation Product Line
SILITECH AG stocks potting compounds of all material classes in its Swiss warehouse—ranging from simple protective encapsulation to high-performance thermally conductive potting compounds.
Silicone potting compounds from Elkem (Bluesil) and Dow
Single-component systems (CAF series)
Elkem's CAF series consists of one-component silicone elastomers that cure at room temperature upon contact with moisture in the air. Ready to use; no mixing required.
| product | Shore A | Temperature range | λ W/(m·K) | kV/mm | Networking & Unique Features |
|---|---|---|---|---|---|
| CAF 4 | 37 | −60 / +225 °C | 0,30 | 21 | Acetate, self-leveling, transparent |
| CAF 33 | 25 | −65 / +250 °C | 0,20 | 19 | Acetate, rigid, black / white / translucent |
| CAF 530 | 34 | −60 / +150 °C | – | 24 | Alkoxy (neutral), primerless, electronics & solar |
| CAF 730 MF | 24 | −55 / +200 °C | – | 19 | Oxim (MEKO-free), neutral, aviation & maintenance |
CAF product numbers do not indicate Shore hardness. CAF stands for "Compound à Froid" (cold-curing compound). The technical data sheet is always the authoritative source for making the correct selection.
Two-component systems (addition curing)
Addition-curing two-component silicones cure via platinum catalysis without producing byproducts. Pot life and cure times can be precisely controlled, with virtually no shrinkage.
| product | Shore A | MV | λ W/(m·K) | kV/mm | special feature |
|---|---|---|---|---|---|
| Bluesil RTV 141 | 50 | 100:10 | 0,16 | 20 | Transparent, optically clear, n=1.406. LED & optoelectronics. |
| Bluesil RTV 147 | 60 | 100:10 | 0,31 | 18 | Thermally conductive, high strength. Encapsulation for electrical engineering. |
| Bluesil RTV 148 (+ 147 B) | 40 | 100:10 | 0,31 | 18 | Lower viscosity, same λ. Miscible with 147 A. |
| Bluesil ESA 7250 | 52 | 10:1 | 0,16 | 20 | Visually clear, 6.2 MPa strength. UL 94 HB. Photovoltaics. |
| Bluesil ESA 7252 UL94 V0 | 48 | 1:1 | 0,42 | 18 | Highest λ value for silicones, flame-retardant. Aerospace & On-Board. |
| DOWSIL EI-2888 UL746C f1 | ~10 | 1:1 | – | 19 | Primerless, optically clear. Outdoor LEDs & displays. |
Which silicone system for which application? For transparent potting: RTV 141, ESA 7250, or DOWSIL EI-2888. When heat dissipation is critical: RTV 147/148 (λ = 0.31) or ESA 7252 (λ = 0.42). For simple sealing without mixing: CAF series. For UL 94 V0 flame retardancy: ESA 7252. For outdoor LEDs without primer: DOWSIL EI-2888.
PU electrical casting resins (SILIRESIN Biothan)
Biobasierte PU-Giessharze auf Basis nachwachsender Rohstoffe. Kennzeichnungsfrei (weder Harz noch Härter), VOC 0,0 %, Schrumpf < 0,1 %.
| product | hardness | λ W/(m·K) | kV/mm | special feature |
|---|---|---|---|---|
| Biothan 2 MD 207 E UL94 V0 | Shore D 80–83 | 0,455 | > 36 | Hard, temperature-stable up to 200 °C, X-ray-stable. Transformers & HV. |
| Biothan 2 MD 2140 | Shore A 25–55 | 0,215 | > 22 | Flexible, cold-resistant down to −45 °C. Variable hardness (MV 2:1–4:1). |
| Biothan 2 MD 2170-200 | Shore 60 D – 80 A | 0,355 | > 30 | Filled with Al(OH)₃ + ZnO. Heat-resistant up to 143 °C (200 hours). |
Noteworthy: With a thermal conductivity of λ = 0.455 W/(m·K) and a UL 94 V-0 rating, Biothan 2 MD 207 E delivers performance that exceeds that of many silicone potting compounds—at a significantly lower price.
Epoxy and hybrid potting compounds (Permabond, Loctite)
Classic epoxides
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Loctite STYCAST 2057M | 2-component epoxy, 100:4.5 | Shore D 90 | – | General-purpose, low-viscosity, machinable. −40/+130 °C. |
| Permabond ET530 | 2-component epoxy, 2:1 | Shore D 77 | 0,40 | Transparent, low yellowing. Tg 50 °C. |
Flexible-modified epoxies (MT Series) — for electronics potting
The Permabonds MT Series combines epoxy chemistry with flexibility. Soft to medium-strength, high elongation at break, good substrate adhesion.
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Permabond MT382 | 2-component epoxy, 2:1 | Shore A 55–85 | 0,47 | Self-leveling, 20–30 kV/mm, elongation 150–200%. |
| Permabond MT3809 | 2-component epoxy, 10:1 | Shore A 75–85 | – | Soft & flexible, low viscosity. Fine-grained casting. |
Thermally Conductive Hybrid Encapsulant
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Permabond MT3836 UL94 V0 | 2K MS polymer, 2:1 | Shore A 60 | 1,05 | Highest λ in the product range. 18–20 kV/mm. BMS, e-mobility. |
MT3836 is particularly suitable for applications where both heat dissipation and flame resistance are required—such as battery management systems, power electronics, and e-mobility charging modules. With a thermal conductivity of λ = 1.05 W/(m·K), it significantly outperforms all other silicone potting compounds in the product range.
Permabond PU structural adhesives (also for potting)
| product | Type | hardness | pot life | special feature |
|---|---|---|---|---|
| Permabond PT326 | 2K PU, 1:1 | Shore D 65–75 | 4–7 min | Thixotropic, 12–20 MPa shear strength. |
| Permabond PT328 | 2K PU, 1:1 | Shore D 60–75 | 15–20 min | Longer pot life for larger volumes. |
thermal pastes
| product | Type | λ W/(m·K) | Temp. | special feature |
|---|---|---|---|---|
| Bluesil PAST 340 | Silicone paste | 0,41 | −40 / +250 °C | Dielectric (15 kV/mm), sensors & resistors. |
| DOWSIL 340 | Silicone paste (ZnO) | 0,67 | up to +177 °C | Does not cure; no oven required. Shelf life: 60 months. |
Selecting Materials Based on Application
| Application | Material | SILITECH product | Why? |
|---|---|---|---|
| LED Modules (Indoor) | silicone | RTV 141 / ESA 7250 | Visually clear, no yellowing |
| Outdoor LED | silicone | DOWSIL EI-2888 | Primerless, UL 746C f1 |
| Automotive (Engine Compartment) | silicone | RTV 147 / ESA 7252 | High T, λ > 0.3 |
| Aerospace | silicone | ESA 7252 | UL94 V0, λ = 0.42 |
| BMS / Power Electronics | MS polymer | MT3836 | λ = 1.05, UL94 V0 |
| Electronics potting (flexible) | Mod. Epoxy | MT382 | λ = 0.47, 20–30 kV/mm |
| Sensors, connectors | Mod. Epoxy | MT3809 | Low viscosity, soft |
| Transformers, High Voltage | PU | Biothan 207 E | Shore D 83, UL94 V0, λ = 0.455 |
| Cable encapsulation | PU | Biothan 2140 | Flexible, adjustable, −45 °C |
| Industrial control | PU / Silicone | Biothan 2170 / CAF 33 | Cost-effective / versatile |
| High-voltage power supply | epoxy | STYCAST 2057M | Shore D 90, tamper-proof |
| Simple Sealing | One-component silicone | CAF 4 / CAF 33 | Ready to use, no mixing required |
Processing instructions
Mixing ratio and dosage
All 2K casting compounds require strict adherence to the mixing ratio. Deviations of more than ±5% result in incomplete curing, a sticky surface, or reduced mechanical strength.
vacuum degassing
Air bubbles significantly reduce dielectric strength and create thermal weak points. Vacuum degassing at 30–50 mbar is essential for high-quality encapsulations. Low-viscosity systems (RTV 141: 4,000 mPa·s) degas more easily than high-viscosity ones (RTV 147: 150,000 mPa·s).
curing
Most silicone potting compounds cure at room temperature, and the curing process can be accelerated by heat: 4 hours at 60 °C, 2 hours at 100 °C, or 1 hour at 150 °C. Heating too quickly (> 3 °C/min) can cause stress cracks.
Caution — Inhibition with addition-cured silicones: Contact with sulfur-containing rubbers, tin-catalyzed silicones, amine-cured epoxies, or tin-stabilized PVC can inhibit platinum catalysis. If in doubt, conduct a preliminary test on a small area.
Frequently asked questions
Can I repair a potted assembly?
Which Shore hardness for which application?
Do I absolutely need a thermally conductive potting compound?
What is the difference between CAF 4 and CAF 33?
Why isn't my addition-cure silicone curing?
Which system is best for outdoor LED lighting?
Request a consultation now
Are you looking for the right encapsulant? Our specialists can advise you on material selection, provide samples, and support your validation process—from your initial inquiry through to production approval.
Contact & Technical Support →SILITECH AG · Worbstrasse 173 · CH-3073 Gümligen · Tel. +41 31 398 50 70 · info@silitech.ch
What are casting compounds?
Potting compounds are liquid or paste-like materials that completely encapsulate electronic assemblies and provide permanent protection once cured. Unlike conformal coatings, which form only a thin protective layer of 25 to 75 micrometers, potting compounds fill the entire cavity around the electronics. The result is solid, long-lasting protection against moisture, vibrations, chemicals, temperature fluctuations, and mechanical stress.
Encapsulants prevent corrosion and electrochemical migration caused by moisture, increase creep current resistance between adjacent conductors, secure components against vibration and shock, dissipate heat effectively in thermally conductive variants, and protect against chemical influences such as oils, fuels, and cleaning agents. In safety-critical applications, they also serve as tamper protection, as encapsulated assemblies cannot be opened without causing damage.
Full encapsulation or selective encapsulation?
Before the material issue is resolved, a fundamental decision must be made: Will the assembly be fully encapsulated (potting) or only selectively coated (encapsulation)?
Potting (full encapsulation)
All electronic components are fully encapsulated in a housing with potting compound. Maximum IP protection (up to IP68/IP69K), uniform heat dissipation, secure mounting, and tamper resistance.
Disadvantages: Higher material consumption, added weight, and, in the case of epoxy, cannot be repaired.
Encapsulation (selective)
Critical areas are selectively coated, while connectors and test points remain accessible. This saves material and weight and allows for component replacement.
Disadvantages: IP protection is limited to IP54–IP67; uncoated areas remain vulnerable.
Rule of thumb: IP68/IP69K required → potting. Repairability required → encapsulation. Power dissipation over 5 W → potting with thermally conductive compound. Weight is a critical factor → encapsulation.
A Comparison of the Three Material Classes
Silicone casting compounds
Silicones are the most versatile class of materials for electronics potting. They remain elastic over an extremely wide temperature range (−60 °C to +200 °C; special grades up to +300 °C). Their low mechanical stress protects sensitive components and solder joints. For LED applications, silicones are often the only sensible choice: Special optical formulations are transparent, do not yellow, and have a suitable refractive index.
Typical applications: LED modules, automotive control units, outdoor electronics, solar inverters, sensor technology, medical electronics, aerospace.
Epoxy casting compounds
Epoxy resins offer the highest mechanical strength (Shore D 70–90), excellent adhesion to metals and ceramics, and the highest dielectric strength (up to 25 kV/mm). The main drawback: virtually irreparable after curing, brittleness during temperature changes, and a narrow temperature range (−40 to +130 °C).
Typical applications: high-voltage power supplies, transformers, ignition electronics, underwater electronics, tamper protection.
Polyurethane casting compounds (PU)
PU falls between epoxy and silicone: a balanced set of properties at the lowest cost. Shore hardness can be adjusted (Shore A 60 to Shore D 50), good abrasion resistance. Main drawbacks: hygroscopic, UV-sensitive, very narrow temperature range (−40 to +120 °C).
Typical applications: Industrial control systems, switching power supplies (indoor), e-mobility chargers, BMS modules, building automation.
Material Comparison: Silicone vs. Epoxy vs. Polyurethane
Rating on a scale of 1–10. Higher = better.
Comparison Table
| property | silicone | epoxy | polyurethane |
|---|---|---|---|
| temperature range | −60 to +200 °C (up to +300) | −40 to +130 °C (up to +150) | −40 to +120 °C |
| Shore hardness | Shore A 15–60 | Shore D 70–90 | Shore A 60 – Shore D 50 |
| Dielectric strength | 15–21 kV/mm | 20–25 kV/mm | 16–22 kV/mm |
| λ (default) | 0.16–0.20 W/(m·K) | 0.2–0.3 W/(m·K) | 0.2–0.3 W/(m·K) |
| λ (filled) | 0.30–0.42 W/(m·K) | up to 5 W/(m·K) | up to 1.5 W/(m·K) |
| chemical resistance | very good | awarded | good |
| UV resistance | awarded | good | moderate |
| repairability | good | very difficult | possible |
| price level | high | medium to high | low to medium |
Thermally conductive encapsulants: The λ value is the deciding factor
Modern electronics operate in increasingly compact spaces with ever-higher power densities. Standard encapsulants tend to act as thermal insulators (0.16–0.20 W/(m·K))—they protect the electronics but at the same time trap heat within the component.
Rule of thumb: In many cases, an increase in operating temperature of 10 K can roughly halve the service life of electronic components.
The λ-value (thermal conductivity, W/(m·K)) describes how well a material conducts heat. Still air: 0.025 — unfilled silicones: 0.16–0.20 — filled silicones: 0.30–0.42 — hybrid systems: up to 1.05 — aluminum: 237.
Thermal conductivity is increased by adding mineral or ceramic fillers: aluminum oxide (Al₂O₃), boron nitride (BN), or silicon carbide (SiC). The higher the filler content, the better the thermal conductivity—but also the higher the viscosity.
Thermal conductivity of all SILITECH encapsulation products
λ values from the manufacturer's TDS. Higher value = better heat dissipation.
When is thermally conductive potting worthwhile? From approximately 1 W of power dissipation per cm² of component surface area. For standard sensors: 0.16–0.20 W/(m·K). For power electronics: 0.30–0.50 W/(m·K). For critical thermal management with fire protection: Permabond MT3836 with 1.05 W/(m·K) and UL 94 V-0.
SILITECH Encapsulation Product Line
SILITECH AG stocks potting compounds of all material classes in its Swiss warehouse—ranging from simple protective encapsulation to high-performance thermally conductive potting compounds.
Silicone potting compounds from Elkem (Bluesil) and Dow
Single-component systems (CAF series)
Elkem's CAF series consists of one-component silicone elastomers that cure at room temperature upon contact with moisture in the air. Ready to use; no mixing required.
| product | Shore A | Temperature range | λ W/(m·K) | kV/mm | Networking & Unique Features |
|---|---|---|---|---|---|
| CAF 4 | 37 | −60 / +225 °C | 0,30 | 21 | Acetate, self-leveling, transparent |
| CAF 33 | 25 | −65 / +250 °C | 0,20 | 19 | Acetate, rigid, black / white / translucent |
| CAF 530 | 34 | −60 / +150 °C | – | 24 | Alkoxy (neutral), primerless, electronics & solar |
| CAF 730 MF | 24 | −55 / +200 °C | – | 19 | Oxim (MEKO-free), neutral, aviation & maintenance |
CAF product numbers do not indicate Shore hardness. CAF stands for "Compound à Froid" (cold-curing compound). The technical data sheet is always the authoritative source for making the correct selection.
Two-component systems (addition curing)
Addition-curing two-component silicones cure via platinum catalysis without producing byproducts. Pot life and cure times can be precisely controlled, with virtually no shrinkage.
| product | Shore A | MV | λ W/(m·K) | kV/mm | special feature |
|---|---|---|---|---|---|
| Bluesil RTV 141 | 50 | 100:10 | 0,16 | 20 | Transparent, optically clear, n=1.406. LED & optoelectronics. |
| Bluesil RTV 147 | 60 | 100:10 | 0,31 | 18 | Thermally conductive, high strength. Encapsulation for electrical engineering. |
| Bluesil RTV 148 (+ 147 B) | 40 | 100:10 | 0,31 | 18 | Lower viscosity, same λ. Miscible with 147 A. |
| Bluesil ESA 7250 | 52 | 10:1 | 0,16 | 20 | Visually clear, 6.2 MPa strength. UL 94 HB. Photovoltaics. |
| Bluesil ESA 7252 UL94 V0 | 48 | 1:1 | 0,42 | 18 | Highest λ value for silicones, flame-retardant. Aerospace & On-Board. |
| DOWSIL EI-2888 UL746C f1 | ~10 | 1:1 | – | 19 | Primerless, optically clear. Outdoor LEDs & displays. |
Which silicone system for which application? For transparent potting: RTV 141, ESA 7250, or DOWSIL EI-2888. When heat dissipation is critical: RTV 147/148 (λ = 0.31) or ESA 7252 (λ = 0.42). For simple sealing without mixing: CAF series. For UL 94 V0 flame retardancy: ESA 7252. For outdoor LEDs without primer: DOWSIL EI-2888.
PU electrical casting resins (SILIRESIN Biothan)
Biobasierte PU-Giessharze auf Basis nachwachsender Rohstoffe. Kennzeichnungsfrei (weder Harz noch Härter), VOC 0,0 %, Schrumpf < 0,1 %.
| product | hardness | λ W/(m·K) | kV/mm | special feature |
|---|---|---|---|---|
| Biothan 2 MD 207 E UL94 V0 | Shore D 80–83 | 0,455 | > 36 | Hard, temperature-stable up to 200 °C, X-ray-stable. Transformers & HV. |
| Biothan 2 MD 2140 | Shore A 25–55 | 0,215 | > 22 | Flexible, cold-resistant down to −45 °C. Variable hardness (MV 2:1–4:1). |
| Biothan 2 MD 2170-200 | Shore 60 D – 80 A | 0,355 | > 30 | Filled with Al(OH)₃ + ZnO. Heat-resistant up to 143 °C (200 hours). |
Noteworthy: With a thermal conductivity of λ = 0.455 W/(m·K) and a UL 94 V-0 rating, Biothan 2 MD 207 E delivers performance that exceeds that of many silicone potting compounds—at a significantly lower price.
Epoxy and hybrid potting compounds (Permabond, Loctite)
Classic epoxides
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Loctite STYCAST 2057M | 2-component epoxy, 100:4.5 | Shore D 90 | – | General-purpose, low-viscosity, machinable. −40/+130 °C. |
| Permabond ET530 | 2-component epoxy, 2:1 | Shore D 77 | 0,40 | Transparent, low yellowing. Tg 50 °C. |
Flexible-modified epoxies (MT Series) — for electronics potting
The Permabonds MT Series combines epoxy chemistry with flexibility. Soft to medium-strength, high elongation at break, good substrate adhesion.
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Permabond MT382 | 2-component epoxy, 2:1 | Shore A 55–85 | 0,47 | Self-leveling, 20–30 kV/mm, elongation 150–200%. |
| Permabond MT3809 | 2-component epoxy, 10:1 | Shore A 75–85 | – | Soft & flexible, low viscosity. Fine-grained casting. |
Thermally Conductive Hybrid Encapsulant
| product | Type | hardness | λ W/(m·K) | special feature |
|---|---|---|---|---|
| Permabond MT3836 UL94 V0 | 2K MS polymer, 2:1 | Shore A 60 | 1,05 | Highest λ in the product range. 18–20 kV/mm. BMS, e-mobility. |
MT3836 is particularly suitable for applications where both heat dissipation and flame resistance are required—such as battery management systems, power electronics, and e-mobility charging modules. With a thermal conductivity of λ = 1.05 W/(m·K), it significantly outperforms all other silicone potting compounds in the product range.
Permabond PU structural adhesives (also for potting)
| product | Type | hardness | pot life | special feature |
|---|---|---|---|---|
| Permabond PT326 | 2K PU, 1:1 | Shore D 65–75 | 4–7 min | Thixotropic, 12–20 MPa shear strength. |
| Permabond PT328 | 2K PU, 1:1 | Shore D 60–75 | 15–20 min | Longer pot life for larger volumes. |
thermal pastes
| product | Type | λ W/(m·K) | Temp. | special feature |
|---|---|---|---|---|
| Bluesil PAST 340 | Silicone paste | 0,41 | −40 / +250 °C | Dielectric (15 kV/mm), sensors & resistors. |
| DOWSIL 340 | Silicone paste (ZnO) | 0,67 | up to +177 °C | Does not cure; no oven required. Shelf life: 60 months. |
Selecting Materials Based on Application
| Application | Material | SILITECH product | Why? |
|---|---|---|---|
| LED Modules (Indoor) | silicone | RTV 141 / ESA 7250 | Visually clear, no yellowing |
| Outdoor LED | silicone | DOWSIL EI-2888 | Primerless, UL 746C f1 |
| Automotive (Engine Compartment) | silicone | RTV 147 / ESA 7252 | High T, λ > 0.3 |
| Aerospace | silicone | ESA 7252 | UL94 V0, λ = 0.42 |
| BMS / Power Electronics | MS polymer | MT3836 | λ = 1.05, UL94 V0 |
| Electronics potting (flexible) | Mod. Epoxy | MT382 | λ = 0.47, 20–30 kV/mm |
| Sensors, connectors | Mod. Epoxy | MT3809 | Low viscosity, soft |
| Transformers, High Voltage | PU | Biothan 207 E | Shore D 83, UL94 V0, λ = 0.455 |
| Cable encapsulation | PU | Biothan 2140 | Flexible, adjustable, −45 °C |
| Industrial control | PU / Silicone | Biothan 2170 / CAF 33 | Cost-effective / versatile |
| High-voltage power supply | epoxy | STYCAST 2057M | Shore D 90, tamper-proof |
| Simple Sealing | One-component silicone | CAF 4 / CAF 33 | Ready to use, no mixing required |
Processing instructions
Mixing ratio and dosage
All 2K casting compounds require strict adherence to the mixing ratio. Deviations of more than ±5% result in incomplete curing, a sticky surface, or reduced mechanical strength.
vacuum degassing
Air bubbles significantly reduce dielectric strength and create thermal weak points. Vacuum degassing at 30–50 mbar is essential for high-quality encapsulations. Low-viscosity systems (RTV 141: 4,000 mPa·s) degas more easily than high-viscosity ones (RTV 147: 150,000 mPa·s).
curing
Most silicone potting compounds cure at room temperature, and the curing process can be accelerated by heat: 4 hours at 60 °C, 2 hours at 100 °C, or 1 hour at 150 °C. Heating too quickly (> 3 °C/min) can cause stress cracks.
Caution — Inhibition with addition-cured silicones: Contact with sulfur-containing rubbers, tin-catalyzed silicones, amine-cured epoxies, or tin-stabilized PVC can inhibit platinum catalysis. If in doubt, conduct a preliminary test on a small area.
Frequently asked questions
Can I repair a potted assembly?
Which Shore hardness for which application?
Do I absolutely need a thermally conductive potting compound?
What is the difference between CAF 4 and CAF 33?
Why isn't my addition-cure silicone curing?
Which system is best for outdoor LED lighting?
Request a consultation now
Are you looking for the right encapsulant? Our specialists can advise you on material selection, provide samples, and support your validation process—from your initial inquiry through to production approval.
Contact & Technical Support →SILITECH AG · Worbstrasse 173 · CH-3073 Gümligen · Tel. +41 31 398 50 70 · info@silitech.ch
