Typical Properties of Multi/Cable Insulations for Multi Conductor Cables
|Resin Compound||PVC||Polyethylene (Unfilled)||Polypropylene (Unfilled)||Nylon||Fluorocarbon|
|Ultimate Tensile Strength, psi||3000||2200||3400||5000||8000||3500||3000|
|Ultimate Elongation, %||200||625||250||200||200||300||250|
|Rated Max Temp, °C||105||75||95||105||120||260||200|
|Rated Min Temp,°C||-40||-65||-65||-40||-40||-65||-65|
|Volume Resistivity, ohm-cm||8 x 10||1 x 10||1 x 10||1 x 10||1 x 10||1 x 10||1 x 10|
|Dielectric Constant, 1k hz||5.0||2.25||2.32||2.22||4.5||2.0||2.1|
Because of its wide range of properties, PVC is typically used either as a dielectric or sheathing or both in applications such as: power distribution cables, building wiring, appliances wiring, flexible cords, high temperature wiring, industrial wiring, coaxial cables.
All of the polyethylenes are excellect dielectrics. Outstanding electrical properties include high insulation resistance, high dielectric strength, low dielectric constant, low dielectric loss at all frequencies, excellent resistance to cold flow, and good abrasion resistance.
Polyethylene is widely used for insulation on telephone signal and control cables, high frequency electronic cables, high and low voltage power cables, line wire, neutral supported secondary and service drop cable.
Low Density Polyethylene (LDPE)
LDPE exhibits good fluid resistance at room temperature. It also has very low water absorption. The mechanical properties of LDPE are not outstanding. Generally, where mechanical abuse is anticipated on relatively thin-walled hook-up wire constructions, a nylon jacket or some other suitable outer covering is usually recommended to improve abrasion and cut-through resistance.
The electrical properties of LDPE are outstanding. It is a low loss material and is used as the dielectric for many coaxial cables in involving high frequency applications. It exhibits good resistance to breakdown under corona and is often used in high voltage applications.
High Density Polyethylene (HDPE)
High density polyethylene has chemical and electrical properties similar to the low density resins. Its fluid resistance is somewhat better. The major difference between the two types lies in the mechanical area. High density resins are harder, stiffer, and better in abrasion and cut-through resistance than the low density resins. These resins are suitable for jackets or sheaths since they have good resistance to environmental degradation.
Polypropylene has a lower density than the polyethylene resins. The chemical and electrical and electrical properties of this polymer are similar to those of the polyethylenes. Its fluid resistance is somewhat superior. Its dielectric constant is somewhat lower than that of LDPE. Polypropylene is considerable harder and stiffer than polyethylene. It also has relatively poor low-temperature flexibility. It can be degraded by heat and light unless protected by antioxidants.
Nylon generally carries a high temperature rating of 150ºC for continuous service. Its low temperature limit is dependent upon the wall thickness and the diameter of the construction. As both of these parameters increase, the susceptibleness to cracking or flexing at low temperatures also increases.
It is non-polar and has outstanding electrical properties. The good electrical properties are combined with very high resistance to chemicals and temperature: service operation up to 260ºC is possible and flexibility remains at very low temperatures. Polymers of TFE possess unexcelled fluid resistance and are attacked only by alkali metals such as barium, sodium, potassium, and by fluorine at high temperatures and pressures.
Fluorinated Ethylene Propylene (FEP)
The low temperature properties of FEP are similar those of TFE and result in a -65ºC rating. The mechanical and electric properties of FEP are also similiar to TFE. However, they deteriorate faster under adverse conditions.