All polyethylenes have excellent dielectrics - high dielectric strength, low dielectric constant, and low dissipation factor at all frequencies.
This makes PE is used across a range of different cable types including telephone and high-speed transmission, high-frequency signal and control cable, low, medium and high voltage power cables, overhead line wire and service drop cables. PE naturally has poor fire resistance it can be significantly improved by the addition of fillers – either halogenated types or halogen-free types. PE can also be compounded to include additives that enhance other properties such as resistance to sunlight, weathering and chemical degradation. PE is a hard and abrasion-resistant material which makes it useful as a sheathing material in various applications but where a more flexible material has required the addition of the small amount of butyl or ethylene propylene rubber (EPR) can improve flexibility. The toughness of the PE also makes it suitable for direct burial in the ground.
The temperature range is typical -65°C to +75°C but cross-linking the polyethylene can extend this temperature range to +90°C.
The benefits of MDPE insulated cables
MDPE stands for medium density polyethylene. This material is used principally as a sheathing material on larger size cables with higher voltage ratings.
Polyethylene materials all have excellent insulation resistance, dielectric strength, low dissipation factors, and abrasion resistance. They are classified by their density which is associated with the crystallinity levels of the polyethylene. The higher the crystallinity or density, the greater the toughness of the cable sheath.
MDPE has very high resistance to abrasion: it is extremely hard and has a low dielectric constant with superior oxidation resistance. The MDPE cable sheathing protects the cable from sharp objects dropped or loaded onto the cable. This means MDPE finds particular usage in transmission cables in the toughest of environments, notably those with the high ambient temperatures found in tropical and subtropical countries.
Various additives can be applied to MDPE compounds to improve fire retardant properties, UV and weathering resistance and the chemical degradation.
Common Types of PE Wire or Cable
Oil and Gas Industry
Networking and Data Wiring