Polyethylene (PE) insulation is widely used in cable design because of its strong electrical properties, low dielectric constant and good moisture resistance. Common PE insulation types include low-density polyethylene, high-density polyethylene, cross-linked polyethylene and foamed polyethylene.
The table below compares typical PE insulation properties. Values are indicative and should be checked against the cable manufacturer’s datasheet for the exact compound and cable construction being specified.
PE insulation material comparison
| Property | LDPE Low-density polyethylene | HDPE High-density polyethylene | VPE / XLPE Cross-linked polyethylene | O2Y Foamed polyethylene |
|---|---|---|---|---|
| Density, g/cm3 | 0.92-0.94 | 0.94-0.98 | 0.92 | ≈0.65 |
| Breakdown voltage, kV/mm at 20 °C | 70 | 85 | 50 | 30 |
| Specific volume resistivity, Ω cm at 20 °C | 1017 | 1017 | 1012-1016 | 1017 |
| Dielectric constant, 50 Hz at 20 °C | 2.3 | 2.3 | 4-6 | ≈1.55 |
| Dielectric loss factor, tan δ | 2 × 10-4 | 3 × 10-4 | 2 × 10-3 | 5 × 10-4 |
| Permanent working temperature, °C | -50 to +70 | -50 to +100 | -35 to +90 | -40 to +70 |
| Short-time temperature, °C | +100 | +120 | +100 | +100 |
| Melt temperature, °C | 105-110 | 130 | – | 105 |
| Flame resistance | Flammable | Flammable | Flammable | Flammable |
| Oxygen index, LOI (% O2) | ≤22 | ≤22 | ≤22 | 18-30 |
| Heating value H0, MJ/kg | 42-44 | 42-44 | 42-44 | 42-44 |
| Thermal conductivity, W/(K·m) | 0.3 | 0.4 | 0.3 | 0.25 |
| Corrosive gases in case of fire | No | No | No | No |
| Radiation resistance, max Mrad | 100 | 100 | 100 | 100 |
| Tensile strength, N/mm2 | 10-20 | 20-30 | 12.5-20 | 8-12 |
| Elongation at break, % | 400-600 | 500-1000 | 300-400 | 350-450 |
| Shore hardness | 43-50 (D) | 60-63 (D) | 40-45 (D) | – |
| Abrasion resistance | Medium | Good | Medium | – |
| Water absorption, % | 0.1 | 0.1 | 0.1 | – |
| Halogen free | Yes | Yes | Yes | Conditional |
| Weather resistance | Medium; black compounds good | Medium; black compounds good | Good | – |
| Cold resistance | Good | Good | Good | Good |
Design notes
PE materials can offer excellent dielectric performance, but the final selection depends on operating temperature, fire performance, mechanical requirements, environmental exposure and the cable standard being applied. XLPE is widely used where a higher operating temperature is required.