Triple insulated litz wire requires insulation materials that offer good thermal-mechanical-electrical stability. For such severe conditions environment, fluoropolymers have been known the best materials and PTFE, FEP, PFA and ETFE are the four most popular ones. 

Although these synthetic polymers have outstanding resistance to chemicals and good dielectric strength, the varying properties of temperature resistance, mechanical strength and the process-ability distinguishes their utilities. With everything from -200°C to +260°C, the temperature range over which PTFE (Polytetrafluoroethylene) can be used is the widest among any of the “plastics”. It exhibits near universal chemical resistance and has the lowest dielectric constant (2.1) of all the fluoropolymers. Also PTFE cannot be processed by melt, instead it must be paste extruded then sintered at high temperature, therefore the processing is complex and costly. For a triple-layer, twisted pairs cable used in aerospace, oil field logging, or semiconductor vacuum device, only PTFE satisfies the thermal and chemical requirements.

FEP reserves more than 80 % of the fundamental nature of the PTFE in spite of being melt processable by the way of typical extrusion. The Dielectric Constant is 2.1 while the Operating Temperature is as high as 200°C. FEP presents better surface finishes and more consistent results along the processing compared with PTFE and it is the most cost efficient fluoropolymer for insulated wire. "It's mainly demanded in wiring harnesses for new energy vehicles and industrial high temperature machinery.

The PFA is a perfluorinated polymer based on the fluoropolymer chemistry of Teflon. It offers excellent creep resistance, ultrahigh purity, and a dielectric constant of 2.1. While costly, PFA is the material of choice for semiconductor tool, medical sterilization cables and aerospace harnesses, in which both extreme temperature resistance and contamination control are necessary. ETFE (Ethylene tetrafluoroethylene) is a random copolymer of TFE (Tetrafluoroethylene) and ethylene and is not a perfluorinated polymer like the ones above: it contains ethylene (which has hydrogen atoms) in the copolymer chain making it less chemically inert and drastically increasing its mechanical toughness. ETFE has the lowest thermal rating of the four, with a continuous processing temperature of 150°C (200°C maximum for short-term use). However, it is more resistant to moisture, vibrations, friction and radiation and its low density (about 1.7g/cm³) make it an ideal candidate for weight saving. ETFE is the preferred airframe wiring in aerospace and is superb for nuclear containment, and dynamic flexing applications.