Wire and Cable Insulation Materials

What is Insulation?

Insulation is a nonconductive material within a cable's construction. It is also often called a dielectric in radio frequency cables.

Insulation resists electrical leakage, which prevents the wire’s current from coming into contact with other wires and cables nearby. It also preserves the material integrity of the wire by protecting against environmental threats such as water and heat. The longevity and effectiveness of a wire depend on its insulation.

What are the different types of Insulation?

There are many different kinds of insulation. The three main categories are Plastic, Rubber, and Fluoropolymer. Following is a list of insulation materials with information on the typical uses, advantages, and disadvantages for each option.

Plastic Insulation

Comparative Properties of Plastic Insulations

Rubber Insulation

Comparative Properties of Rubber Insulations

Fluoropolymer Insulation

Comparative Properties of Fluoropolymer Insulations

Plastic Insulation Types

Polyvinyl Chloride (PVC)

  • PVC is a relatively inexpensive and easy-to-use material with the potential to be used in diverse applications. PVC has a temperature range of -55° Celsius to +105° Celsius and is resistant to flame, moisture, and abrasion. It can also endure exposure to gasoline, ozone, acids, and solvents.
  • PVC can be used for medical and food-related purposes as it is odorless, tasteless, and nontoxic. PVC insulation can be used in heavy- and thin-wall applications. However, it should not be used when flexibility and extended flex life are required at low temperatures. When used in retractile cord applications, it shows below-average flexibility. PVC displays high attenuation and capacitance loss, meaning that power is lost when used in an electrical system.

Semi-Rigid PVC (SR-PVC)

  • Semi-Rigid PVC is mainly used as primary insulation and is very abrasion-resistant. (For 30-16 gauge, a 10-mil. wall meets UL style 1061, 80 degrees Celsius, 300 volts.) Semi-rigid PVC is also resistant to heat, water, acid, and alkali. It is also flame-retardant.

Plenum Polyvinyl Chloride (Plenum PVC)

  • Plenum PVC is suitable for use in plenum spaces -- building spaces behind dropped ceilings or raised floors left open to allow for air circulation. Standard PVC is considered a non-plenum insulation option because it does not exhibit the qualities necessary for safe usage in plenum areas. To be plenum-rated, the insulation must meet more-stringent fire safety regulations.

Polyethylene (PE)

  • PE is mostly used in coaxial and low-capacitance cables because of its exemplary electric qualities. It is often used in these applications because it is affordable and can be foamed to reduce the dielectric constant to 1.50. This makes PE a popular option for cables requiring high-speed transmission.

  • PE can also be cross-linked to produce high resistance to cracking, cut-through, soldering, and solvents. It can be used in temperatures ranging from -65° Celsius to +80° Celsius. All densities of PE are stiff, hard, and inflexible. This material is also flammable. Additives can be used to make it flame-retardant, but this will sacrifice the dielectric constant and increase power loss.

Polypropylene (PP)

  • PP is very similar to PE but has a wider temperature range of -30° Celsius to +105° Celsius. It is used primarily for thin-wall primary insulations and can be foamed to improve its electrical properties.

Polyurethane (PUR)

  • PUR is known for its extreme toughness, flexibility, and flex life even in low temperatures. It also has excellent ratings for chemical, water, and abrasion resistance. This material works well in retractile cord applications and is a popular option for salt-spray and low-temperature military purposes.
  • PUR is a flammable material. It can be made flame-retardant, but this sacrifices strength and surface finish. PUR's main disadvantage, however, is its poor electrical properties. Because of this, it is used for jackets more than insulation.

Chlorinated Polyethylene (CPE)

  • CPE has very good heat, oil, and weather resistance. CPE serves as a lower-cost, more environmentally friendly alternative to CSPE. Its reliable performance when exposed to fire also makes it a favorable alternative to PVC insulation. CPE is commonly found in power and control cables as well as industrial power plant applications.

Nylon

  • Nylon is usually extruded over softer insulation compounds. It serves as a tough jacket, exhibiting strong abrasion, cut-through, and chemical resistance, especially in thin-wall applications. It is also extremely flexible. One disadvantage of nylon is its absorption of moisture. This degrades some of its electrical properties.

Comparative Properties of Plastic Insulations

PVC PE LD
PE
Cellular
PE
HD
PE
PP Cellular
PUR
PVC Plenum
Nylon
CPE
Oxidation Resistance E E E E E E E E E E
Heat Resistance G-E G G E E E G G-E E E
Oil Resistance F G-E G G-E F F E F E E
Low-Temperature Flexibility P-G E E E P P G P-G G E
Ozone Resistance E E E E E E E E E E
Weather (Sun Resistance) G-E E E E E E G G E E
Abrasion Resistance F-G G F E F-G F-G O F-G E E-O
Electrical Properties F-G E E E E E P G P E
Flame Resistance E P P P P P P E P E
Nuclear Radiation Resistance F G-E G G-E F F G F F-G O
Water Resistance F-G E E E E E P-G F P-F O
Acid Resistance G-E G-E G-E E E E F G P-F E
Alkali Resistance G-E G-E G-E E E E F G E E
Alcohol Resistance P-E E E E E E P-G G P E
Aliphatic Hydrocarbons Resistance P G-E G G-E P-F P P-G P G E
Aromatic Hydrocarbons Resistance P-F P P P P-F P P-G P-F G G-E
Halogenated Hydrocarbon Resistance P-F G G G P P P-G P-F G E
Underground Burial F-G G - G - - G P - P
P = POOR F = FAIR G = GOOD E = EXCELLENT O = OUTSTANDING

Rubber Insulation Types

Thermoplastic Rubber (TPR)

  • In many applications, TPR is used to replace true thermoset rubber. It has improved colorability, higher processing speeds, and a wider usable temperature range. It also displays excellent heat, weather, and age resistance without curing. TPR is not cut-through resistant but can be used in applications where other properties of rubber are preferred.

Neoprene (Polychloroprene)

  • Neoprene is a synthetic thermoset rubber that must be vulcanized to obtain its desired qualities. It exhibits supreme abrasion, cut-through, oil, and solvent resistance. Neoprene is also known for its long service life, wide temperature range, and usability. It is remarkably flame retardant and self-extinguishing. Neoprene is especially desirable for hand-held cord sets and is often used in Military products.

Styrene-Butadiene Rubber (SBR)

  • SBR is a thermoset compound with qualities similar to neoprene. It has a temperature range of -55° Celsius to +90° Celsius. SBR is primarily used in Mil-C-55668 cables.

Silicone

  • Silicone is extremely heat-resistant, flame-retardant, and can be used in temperatures up to +180° Celsius. It is moderately abrasion-resistant and extremely flexible. Benefits include a long storage life and good bonding properties, which are necessary for many electrical applications.

Fiberglass

  • Fiberglass is the most widely used glass insulation. It can be used continuously in temperatures up to +482° Celsius. This material is resistant to moisture and chemicals but is only fairly abrasion-resistant. Its common applications include heat treating, glass and ceramic kilns, foundries, and extensive applications in aluminum processing.

Ethylene Propylene Rubber (EPR)

  • EPR is known for its excellent thermal characteristics and electrical properties, allowing a smaller cross-sectional area for the same load-carrying capacity of other cables. It is commonly used in high-voltage cables. EPR is heat, oxidation, weathering, water, acid, alcohol, and alkali resistance.
  • The flexibility of this material also makes it appropriate for temporary installations and applications in the mining industry. EPR has a temperature range of -50° Celsius to +160° Celsius but is not as tear-resistant as other insulation options. It is also relatively soft and may require more care during installation to avoid damage.

Rubber

  • Rubber insulation generally refers to both natural rubber and SBR compounds, each available in a variety of formulas for use in a wide range of applications. Because formulas vary, so do temperature ranges and some other basic characteristics. While this type of insulation has poor oil and ozone resistance, it exhibits good low-temperature flexibility, electrical properties, and water, alcohol, and abrasion resistance.

Chlorosulfonated Polyethylene (CSPE)

  • CSPE works well as low-voltage insulation. It is known for its ability to perform in a wide temperature range and its resistance to chemicals and UV rays. This insulation material can be found in appliance wire, lead wire, coil leads, transformer leads, and motor lead wire. CSPE is also referred to as Hypalon, a registered trademark of Dupont.

Ethylene Propylene Diene Monomer (EPDM)

  • This synthetic rubber insulation displays outstanding heat, ozone, weather, and abrasion resistance. EPDM also exhibits excellent electrical properties. Further benefits include excellent flexibility at both high and low temperatures, from -55° Celsius to +150° Celsius, as well as good dielectric strength. EPDM is used as a replacement for silicone rubber in some applications.

Comparative Properties of Rubber Insulations

Rubber Neoprene CSPE EPDM Silicone
Oxidation Resistance F G E E E
Heat Resistance F G E E O
Oil Resistance P G G P F-G
Low-Temperature Flexibility G F-G F G-E O
Ozone Resistance P G E E O
Weather (Sun Resistance) F G E E O
Abrasion Resistance E G-E G G P
Electrical Properties G P G E G
Flame Resistance P G G P F-G
Nuclear Radiation Resistance F F-G E G E
Water Resistance G E E G-E E
Acid Resistance F-G G E G-E F-G
Alkali Resistance F-G G E G-E F-G
Alcohol Resistance G F G P G
Aliphatic Hydrocarbons Resistance P G F P P-F
Aromatic Hydrocarbons Resistance P P-F F F P
Halogenated Hydrocarbons Resistance P P P-F P P-G
P = POOR F = FAIR G = GOOD E = EXCELLENT O = OUTSTANDING

Fluoropolymer Insulation Types

PFA

  • PFA has different temperature ratings depending on the cables' construction, ranging from -65° Celsius to +250° Celsius. It also has a very low dissipation factor, making it an electrically efficient option. It does not exhibit thermoset qualities, limiting it to use only in select applications. Although PFA can be processed in long lengths, it is also an expensive material.

Polytetrafluoroethylene (PTFE)

  • PTFE is a thermoplastic material that has a temperature range of -73° Celsius to +204° Celsius. It is extremely flexible, as well as resistant to water, oil, chemicals, and heat. The mechanical properties of PTFE are low compared with other fluoropolymer materials.

Fluorinated Ethylene Propylene (FEP)

  • This material is mostly used because of its processing characteristics and a wide range of application uses. It is also highly flame-resistant. Improved data transmission can also be achieved when FEP is foamed. Pricing and processing are also being improved. FEP is commonly used in plenum cable and military applications.

ETFE and ECTFE Halar

  • These materials are stronger and more flexible than PFA or FEP and can become thermoset through irradiation. Foaming ECTFE and ETFE improves data transmission and reduces weight. However, ETFE and ECTFE lack many of the electrical advantages of FEP.

Polyvinylidene Fluoride (PVDF)

  • PVDF is a flexible, lightweight, and thermally stable material. It is also resistant to chemicals, heat, weather, abrasion, and fire. PVDF is a relatively low-cost insulation option, so it is used in a wide range of industries and applications. It is often found in cables that need to meet the UL standard 910 Plenum Cable Flame Test, which labels cables as suitable for use in a building’s space for air circulation. PVDF is also commonly called Kynar, a registered trademark of Arkema Inc.

Thermoplastic Elastomers (TPE)

  • Thermoplastic elastomers consist of a mix of polymers, typically plastic and rubber, to combine the benefits of each material into one insulating product. TPE can be molded, extruded, and reused like plastic materials while maintaining the flexibility and stretch of rubber.
  • TPE is commonly used in applications where conventional elastomers cannot provide the necessary range of physical properties. TPE is now being used more and more in automotive applications and household appliances. Disadvantages of TPE include poor chemical and heat resistance, low thermal stability, and a higher cost than other types of insulation.

Comparative Properties of Fluoropolymer Insulations

FEP ETFE PTFE PVDF ECTFE TPE
Oxidation Resistance O E O O O E
Heat Resistance O E O O O E
Oil Resistance O E E-O E O G
Low-Temperature Flexibility O E O F O E
Ozone Resistance E E O E E E
Weather (Sun Resistance) O E O E-O O E
Abrasion Resistance E E O E E F-G
Electrical Properties E E E G-E E E
Flame Resistance O G E E E-O F-G
Nuclear Radiation Resistance P-G E P E E G
Water Resistance E E E E E G-E
Acid Resistance E E E G-E E G
Alkali Resistance E E E E E G-E
Alcohol Resistance E E E E E G
Aliphatic Hydrocarbons Resistance E E E E E P
Aromatic Hydrocarbons Resistance E E E G-E E P
Halogenated Hydrocarbonic Resistance E E E G E -
Underground Burial E E E E E P
P = POOR F = FAIR G = GOOD E = EXCELLENT O = OUTSTANDING