Typical Characteristics of Popular Insulation & Jacketing Compounds

CSPE Chlorosulfinated Polyethylene 

CSPE is better known as Hypalon (a DuPont trademark). Used as a 105°C rated motor lead wire insulation, but is primarily a jacketing compound. It has excellent tear and impact strength, excellent abrasion, ozone, oil, and chemical resistance and good weathering properties. The material also has low moisture absorption, excellent resistance to flame and heat, and good dielectric properties.

EPDM (ethylene-propylene-diene elastomer) is a chemically cross-linked elastomer with excellent flexibility at high and low temperatures (150° to –55°C). It has good insulation resistance and dielectric strength, as well as excellent abrasion resistance and mechanical properties. EPDM also has better cut-through resistance than Silicone rubber, which it replaces in some applications. 

EPDM is compatible with most varnishes, but after the dip and bake cycle varnish tends to adhere to the insulation (because EPDM, unlike some rubber insulations, does not exude oils or waxes). As lead wires are pulled apart for termination, the varnish cracks, sometimes breaking the insulation. To resolve this problem, a stearic solution is applied to the lead wire during the put-up process. This ensures that rigid varnish does not cause EPDM insulation to rupture when the wire is terminated. Field evaluations by numerous users reveal that the coated EPDM has excellent varnish resistance at least equal to synthetic elastomers, cross-link polyethylene, or Silicone glass braid in dip and bake systems.

A very good insulation in terms of electrical properties. Low dielectric constant, a stable dielectric constant over all frequencies, very high insulation resistance. In terms of flexibility, polyethylene can be rated stiff to very hard, depending on molecular weight and density—low density being the most flexible, with high-density, high-molecular weight formulation being very hard. Moisture resistance is rated excellent. Correct Brown and Black formulations have excellent weather resistance. The dielectric constant is 2.3 for solid insulation and typically 1.64 for foam designs. Flame retardant formulations are available with dielectric constants ranging from about 1.7 for foam flame retardant to 2.58 for solid flame retardant polyethylene. 

Similar in electrical properties to polyethylene. This material is primarily used as an insulation material. Typically, it is harder than polyethylene. This makes it suitable for thin wall insulations. UL maximum temperature rating may be 60°C or 80°C. Most UL styles call for 60°C maximum. The dielectric constant is 2.25 for solid and typically 1.55 for foam designs.

This material is used primarily as a cable jacket material. It has excellent oxidation, oil, and ozone resistance. Some formations also have good flame resistance. It is a hard material with excellent abrasion resistance. It has outstanding “memory” properties, making it an ideal jacket material for retractile cords.

The temperature range of this material can vary from –55°C to 90°C. The actual range would depend on the formulation used. Neoprene is both oil-resistant and sunlight resistant, making it ideal for many outdoor applications. The most stable colors are Black, Dark Brown, and Gray. The electrical properties are not as good as other insulation materials. Because of this, thicker insulation should be used. Typical designs where this material is used are lead wire insulation and cable jackets.

Sometimes referred to as vinyl or polyvinylchloride. Extremely high or low temperature properties cannot be found in one formulation. Certain formulations may have –55°C to 105°C rating. Other common vinyls may have –20°C to 60°C. There are many formulations for the variety of different applications. The many varieties of PVC also differ in pliability and electrical properties. The price range can vary accordingly. Typical dielectric constant values can vary from 3.5 to 6.5.

• Standard PVC is the 1000 volt or less plastic for hook-up, computer and control wires. Different compounds are used for 60°C, 80°C, 90°C and 105°C service, and for commercial and military applications.
• Semi-Rigid PVC is much tougher than standard vinyl. It has greater resistance to abrasion and cut-through and more stable electrical properties.
• Irradiated PVC has improved resistance to abrasion, cut-through, soldering and solvents. Irradiation changes the vinyl from a thermoplastic to a thermosetting material.

The description of rubber normally includes natural rubber and SBR compounds. Both of these materials can be used for insulations and jackets. There are many formulations of these basic materials. Each formulation is for a specific application. Some formulations are suitable for –55°C minimum, while others are suitable for 75°C maximum.

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's resistance to compression, cutting, impact, tearing and abrasion is good. EPR is not attacked by acids, alkalis and many organic solvents. It is also highly moisture resistant. It has temperature ratings up to 150°C.

Thermoplastic rubber has properties similar to those of vulcanized (thermosetting) rubbers. The advantage is that processed like thermoplastics, it is extruded over the conductor. Like many conventional rubber materials, TPR is highly resistant to oils, chemicals, ozone and other environmental factors. It has low water absorption and excellent electrical properties, and is very flexible with good abrasion resistance.

This is a very soft insulation which has a temperature range from –80°C to 200°C. It has excellent electrical properties plus ozone resistance, low moisture absorption, weather resistance, and radiation resistance. It typically has low mechanical strength and poor scuff resistance.

Nylon

Nylon exhibits excellent jacket toughness, especially in thin-wall applications, and has excellent abrasion, cut-through, and chemical resistance. Its main application is to provide these qualities when extruded over softer insulation compounds. Nylon* has a very low coefficient of friction, making it a good choice for use in high flex applications.

Nylon does absorb moisture, which somewhat degrades its electrical properties from their original state.

Cross-Linked Polyethylene is rated up to 150°C. Cross-linking changes thermoplastic polyethylene to a thermosetting material which has greater resistance to environmental stress cracking, cut-through, ozone, solvents and soldering than either low or high density polyethylene. Sometimes it is designated as XLPE. Can be cross-linked either chemically or irradiated.

This material has excellent electrical properties, temperature range and chemical resistance. It is not suitable where subjected to nuclear radiation and does not have good high voltage characteristics. FEP Teflon is extrudable in a manner similar to PVC and  polyethylene. This means that long wire and cable lengths are available. TFE Teflon is extrudable in a hydraulic ram type process. Lengths are limited due to amount of material in the ram, thickness of the insulation, and preform size. TFE must be extruded over  a silver- or nickel coated wire. The nickel- and silver-coated designs are rated 260°C and 200°C maximum, respectively. The cost of Teflon is approximately 8 to 10 times more per pound than PVC compounds.

Fluorocopolymer thermoplastic material having excellent electrical properties, heat resistance, chemical resistance, toughness, radiation resistance, and flame resistance. The temperature rating is –65°C to 150°C. 

Kynar has great mechanical strength, superior resistance to abrasion and cut-through and substantially reduced cold-flow which makes it an excellent back plane wire insulation. Kynar is self-extinguishing and radiation resistant.

Thermoplastic fluoropolymer material with excellent chemical resistance, electrical properties, thermal characteristics, and impact resistance. The temperature rating is –70°C to 150°C.