Quick3D Dielectric strength
Dielectric strength is how much voltage a material can block before it breaks down. Learn how it is tested and why thickness matters.
What it means in practice
Dielectric strength is the electric field an insulating material can withstand before current punches through it. Above that point the material breaks down, often leaving a tiny burnt channel, and stops insulating.
Key takeaways
- Dielectric strength is the electric field an insulator withstands before current punches through.
- Thin samples read higher per mm, so compare values at similar thickness.
- Printed walls with voids usually insulate less well than moulded test plaques.
- A dielectric value alone does not make a design safe; test the finished part.
It matters for printed parts that separate live conductors from each other or from people:
- Insulating spacers, bushings and standoffs.
- Housings for power supplies, battery packs and chargers.
- Coil formers and bobbins.
- Test fixtures and probe holders that touch high-voltage circuits.
Watch out
Conductive and ESD-safe materials are the opposite. They are not insulators and should not be used where insulation is needed.
How it’s measured
A flat sample sits between two electrodes, often under oil to stop sparks running around the edge. The voltage is raised until the sample breaks down. The breakdown voltage divided by the sample thickness gives the dielectric strength.
- Standards: IEC 60243-1 and ASTM D149. Both allow a quick, steady ramp (short-time method) or slower step-by-step methods.
- Units: kV/mm. US sheets often use volts per mil; 1 kV/mm is about 25.4 V/mil.
How to read and compare it
- Thickness changes the number. Thin samples usually give a higher kV/mm than thick ones. Doubling wall thickness does not double the voltage a part can block. Compare values measured at similar thickness.
- Method and conditions. Short-time tests give higher values than slow step tests. AC and DC results differ. Humidity, temperature and the surrounding medium also matter.
- Printed parts have voids. Gaps between extrusion lines and layers can hold air, which breaks down more easily than solid plastic. Printed walls usually insulate less well than a moulded test plaque. Use 100% infill and generous wall thickness for insulating parts.
- Moisture. Water-absorbing materials such as nylon lose insulation as they take up moisture.
- Not the whole story. Electrical safety also depends on creepage and clearance distances, tracking resistance and flammability. A dielectric value alone does not make a design safe. Follow the safety standard for your product and test the finished part.
Range in our catalog
Few datasheets report dielectric strength, so the sample is small.
- All materials: 4.38–172 kV/mm (median 19.75 kV/mm, 26 materials)
- Resins: 15–37 kV/mm (median 17.9 kV/mm, 15 materials)
- Powders (SLS and MJF): 4.38–42 kV/mm (median 27 kV/mm, 5 materials)
- Engineering materials: 7.6–42 kV/mm (median 28 kV/mm, 14 materials)
- Resin 1515–37
- Filament 66.05–172
- Powder 54.38–42
Bar = lowest to highest, dot = median. 26 materials, live from our database.
Highest and lowest in our catalog
Highest dielectric strength
| Material | Polymer | Dielectric strength |
|---|---|---|
| 3D4Makers PI Z2 | PI | 172 kV/mm |
| Ultrasint PP 1400 Black | PP | 42 kV/mm |
| Ultracur3D RG 35 | Photopolymer | 37 kV/mm |
| Ultracur3D SLA 7700 | Photopolymer | 34 kV/mm |
| Ultrafuse PC/ABS FR Black | PC/ABS | 33 kV/mm |
Lowest dielectric strength
| Material | Polymer | Dielectric strength |
|---|---|---|
| Ultrasint TPU 01 | TPU | 4.38 kV/mm |
| Fiberon PPS-GF20 | PPS | 6.05 kV/mm |
| HP 3D HR PA 12 FR | PA12 | 7.6 kV/mm |
| Formfutura PPSU | PPSU | 15 kV/mm |
| Somos WaterClear Ultra 10122 | Photopolymer | 15 kV/mm |
Tip
Check the thickness and method on each datasheet before ranking materials by these values.
Related properties
- Surface resistivity and ESD — how charge moves across a surface.
- Flame retardancy (UL 94) — usually required for electrical housings too.
- Heat deflection temperature — for parts near warm components.
- Glass transition temperature — electrical and mechanical behaviour both shift as a plastic nears it.
See flame-retardant materials for electrical housings 37 materials