Fluorocarbons and Insulation
Now that we’ve discussed the different types of thermoplastic insulation compounds, let’s talk about Fluorocarbon insulation. These compounds contain fluorine in the molecular structure, thus having less hydrogen atoms. Below are some examples of materials used in wire and cable insulation construction.
Tetrafluoroethylene (TFE): Used as both insulation and jacket and has a maximum continuous operating temperature rating of 260°C and a maximum intermittent operating temperature range of 316°C, TFE was first produced by DuPont Corporation in the late 1930’s. Originally developed for military applications in the late 1940’s, TFE found its way into commercial markets. TFE offers excellent chemical resistance and good electrical properties; however, it can’t be extruded using conventional extrusion equipment like those used for thermoplastics. TFE requires special ram extrusion equipment that uses high pressure as opposed to high heat, which sets it apart from the more conventional heat extrusion models. Since TFE can’t be melt extruded, it is impossible to have long continuous lengths. The only way to fabricate relatively long lengths is to form the material into rolls of TFE tape. Once it is in the form of a tape, then it can be applied helically around a conductor and would have to pass through 600°C sintering towers to fuse the tape edge together. Due to the high heat needed for tape fusing, the conductor must be either silver or nickel coated, since tin coating would oxidize at best or melt at worst.
Fluorinated Ethylene-Propylene (FEP): FEP was developed to offset some of the shortcomings of TFE. It has a maximum continuous operating temperature rating of 200°C with a maximum intermittent operating temperature of 232°C. An advantage of FEP compared to TFE is that it can be heat extruded using conventional extrusion equipment.
Ethylene-Tetrafluoroethylene-Copolymer (ETFE): ETFE is a modified copolymer of tetrafluoroethylene and ethylene and provides excellent chemical and abrasion resistance as well as mechanical strength. The maximum continuous operating temperature rating is 150°C and the maximum intermittent operating temperature is 199°C. ETFE also has a low dielectric constant, so it has good electrical properties.
Polyvinylidene Fluoride (PVDF): This compound has a temperature range of -40°C to 150°C and affords high resistance to acids and alkalis. It also has high impact resistance and tensile strength. PVDF is a very stable and pure resin, which is used in several industries, such as electrical and electronic manufacturing, tubing, piping and those products used for handling fluids.
ECTFE: This is a copolymer of ethylene and chlorotrifluoroethylene that provides excellent chemical and abrasion resistance. It can be used for those applications where one requires better performance than offered by PVDF.
Our next blog will discuss the final grouping of popular insulation materials, thermosets.