If you’re using silicone sheets near electrical components without knowing their dielectric rating, you’re taking a serious risk.
Silicone sheets have high dielectric strength, typically ranging from 20 to 30 kV/mm, making them ideal insulators in electrical and electronic applications.
I started paying attention to dielectric strength after a client experienced a short circuit in a control box. Turns out the gasket they used wasn’t insulating enough. That experience taught me how critical dielectric properties are when working with silicone sheets in electrical environments.
What Is Dielectric Strength in Silicone Sheets?
Dielectric strength isn’t just a number—it’s a safety guarantee.
Dielectric strength is the maximum voltage a material can withstand without breaking down electrically; for silicone sheets, it’s typically between 20–30 kV/mm.
Dielectric strength is measured in kilovolts per millimeter (kV/mm). It tells you how much voltage the material can resist before it conducts electricity. Silicone has excellent insulation properties because of its molecular structure, which remains stable even at high temperatures and in humid environments.
For example:
- A silicone sheet rated at 25 kV/mm and 1 mm thick can resist up to 25,000 volts before breakdown.
- Thicker sheets offer more voltage resistance, but other factors like temperature and moisture still affect performance.
When I worked on an LED lighting system, we used 2mm silicone pads with 24 kV/mm dielectric strength. It provided both thermal and electrical insulation in one layer, saving space and reducing parts.
Why Is Silicone Preferred for Electrical Insulation?
I once used PVC for insulation—until it cracked under heat. That’s when I switched to silicone and never looked back.
Silicone is preferred in electrical systems because it maintains insulation properties across wide temperature ranges and doesn’t degrade under UV or moisture.
Unlike other polymers, silicone doesn’t carbonize or melt when exposed to high temperatures. That’s why it’s ideal for environments where both heat and electricity are involved, such as:
- Power distribution boxes
- Control panels
- Motor windings
- High-voltage connectors
Here’s a quick comparison:
| Material | Dielectric Strength (kV/mm) | Temp Resistance | Flexibility | UV Resistance |
|---|---|---|---|---|
| Silicone | 20–30 | –60°C to +230°C | Excellent | Excellent |
| PVC | 10–18 | –20°C to +70°C | Poor | Poor |
| Rubber (EPDM) | 10–15 | –40°C to +120°C | Good | Fair |
I recommend silicone sheets for electrical sealing whenever the system includes heat, UV exposure, or needs to operate continuously. It’s more expensive up front—but lasts far longer.
How Is Dielectric Strength Measured in Silicone?
Before I trusted any supplier’s spec sheet, I had to learn how these numbers are tested.
Dielectric strength is measured by applying an increasing voltage across a silicone sheet until electrical breakdown occurs—according to ASTM D149 or IEC 60243 standards.
The standard procedure includes:
- Using two metal electrodes on both sides of the silicone sample
- Applying voltage gradually until electrical arcing or puncture occurs
- Recording the voltage and dividing by the material thickness to get kV/mm
Several factors affect the result:
- Material thickness: Thinner samples show higher kV/mm values
- Humidity and surface condition: Moisture or contaminants can reduce insulation
- Temperature: Testing is usually done at 23°C unless otherwise specified
Always check whether the dielectric strength quoted is average, minimum, or initial test result. I once got caught out by a supplier quoting lab-only values, not actual production material ratings.
What Applications Rely on Silicone’s Dielectric Ratings?
One of my clients needed a thermal pad for a battery management system—but also needed electrical isolation. Silicone did both.
Applications such as transformers, switchgear, power supplies, and electric vehicles rely on silicone’s dielectric strength for insulation and safety.
Here are some examples:
- Transformers: As insulation between windings and casings
- Electric motors: For slot liners and end-turn protection
- Solar panels: As a non-conductive, weatherproof backing layer
- EV battery systems: Silicone pads separate modules and prevent short circuits
I’ve personally used silicone sheets in:
- Control panels in industrial food machinery
- High-voltage inverter cabinets
- Electric mobility scooters—under seats and battery covers
For all of these, one sheet provided both thermal insulation and electrical protection, reducing part count and installation time.
What Thickness and Hardness Are Best for Electrical Insulation?
I made the mistake once of using a soft 1mm sheet for a high-voltage pad. It compressed too much and failed the insulation test.
For effective dielectric insulation, use silicone sheets between 1–3 mm thick with Shore A hardness of 50–70, depending on pressure and temperature conditions.
Thickness affects both mechanical strength and dielectric capacity. Here’s a basic reference:
| Thickness (mm) | Typical Dielectric Rating (kV) | Use Case |
|---|---|---|
| 0.5 mm | ~12–15 kV | Low-voltage electronics |
| 1 mm | ~20–25 kV | Control panels, battery insulation |
| 2 mm | ~35–40 kV | High-voltage enclosures |
| 3 mm | ~50+ kV | Transformers, motor windings |
Hardness affects compressibility. If the silicone is too soft, it may deform under load and reduce spacing between conductive parts. For most electrical applications, 60 Shore A is the safe middle ground.
Always ask your supplier for certified dielectric test data based on actual thickness—not just theoretical values.
How Do I Select a Reliable Silicone Sheet for Electrical Use?
I once bought cheap silicone sheets from a general supplier—then failed UL testing because the insulation broke down at 15 kV.
Choose silicone sheets from certified suppliers who offer test reports, consistent quality, and customization options for electrical applications.
Here’s what I now demand from any supplier:
- Tested to ASTM D149 or IEC standards
- UL 94 V-0 flame rating (for fire safety)
- Available in various thicknesses and durometer options
- Backed with technical support
- Optional adhesive backing or thermal conductivity
RuiYang Silicone manufactures silicone sheets specifically designed for electrical applications. Our products are tested for dielectric strength, meet flame retardancy standards, and are available in cut-to-size options. Whether you’re building control panels, EV batteries, or industrial power systems—we’ve got the sheet that fits.
Conclusion
Silicone sheets with high dielectric strength offer reliable, long-term insulation for electrical and high-voltage applications.
