When buying bulk cables or cable assemblies, you’re probably concerned about things like conductor AWG size, shielding for EMI/RFI, connector molding construction, etc. Why would you spare a thought to the jacket that just goes around the conductors? Actually, cable jacket is much more important than you may think. Choosing the wrong cable jacket can have implications in a range of things, from extending the life of your cable, to using the cable in the field. The following part will briefly introduce several commonly used cable jackets for your references.
The Importance of Cable Jacket
The cable jacket is the first line of mechanical, moisture, flame and chemical defense for a cable. More specifically, the jacket provides protection for the shielding and conductors. It protects the cable from mechanical damage during and after installation. Jackets are not intended to replace cable armors, but they can provide a fairly high level of moisture and chemical protection along with UV and ozone protection. The following image shows the structure of optical cable.
Commonly Used Cable JacketsPVC
PVC (polyvinyl chloride) is the most widely used nonmetallic jacketing material in the wire and cable industry. Starting in 1935, when it first became available, the use of PVC grew rapidly because of its low cost, easy processing and excellent combination of overall properties including fire and chemical resistance. Nevertheless this kind of jacket also has shortcomings. For example, PVC is a thermoplastic material, so it cannot take high temperature. In industries that handle large amounts of heated material, or where there are the possibilities of excessive heat, the use of PVC should be avoided, because of its tendency to melt or deform when heated to a high temperature.
Increasing concern for worker safety and electronic circuit life circle is driving demand for low-smoke,zero-halogen (LSZH) material. LSZH is composed of thermoplastic or thermoset compounds which will emit limited smoke and no halogen when wires or patch cables are damaged by fire or a short circuit fault. This type of jacket is typically used in poorly ventilated areas such as aircraft, rail cars, or ships. It is becoming very popular and, in some cases, a requirement where there is a need for the protection of people and equipment from toxic and corrosive gas.
Polyurethane, also referred to as PUR, is a thermoplastic material, commonly used in harsh environment. PUR is resistant to swelling and degradation when exposed to water for a long period of time, making it suitable for undersea equipment, like submarine cables. Besides, its flexibility and hardness allow it become a useful compound for isolating electronic components from vibration and shock. However, the only demerit of PUR jacket is that it is more expensive than other types of common jackets.
EPR (ethylene propylene rubber) is a chemically cross-linked, thermosetting high-temperature rubber insulation. It has excellent electrical properties combined with outstanding thermal stability and flexibility. It can also withstand the cold temperature down to -60 Celsius degree. With fairly good high-temperature characteristics overall, when formulated correctly, EPR can be rather flame retardant as well.
As a form of synthetic rubber, silicon has excellent electrical properties plus ozone resistance, low moisture, weather and radiation resistance. While silicon rubber burns slowly, it forms a non-conductive ash which, in some cases, can maintain the integrity of the electrical circuit. Silicon jacket is typically used for applications where lots of wire bending are required.
Cable jacket is not as simple as you think. When you choose patch cables or coppers, you should also take jacket factor into consideration. There are various types of cable jackets available on the market and each of them can be used in different circumstances. After reading this passage, hope you can choose the best one for your applications.