Safety First: Why Paste-Extruded PTFE is Essential to Wire and Cable Construction in Aerospace

The qualities provided by VERSIV? Extruded PTFE Films are of tremendous value to the world’s aerospace wire and cable applications. ?

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Indeed, without these films, there would be a severe challenge for aeronautical engineers in ensuring aircraft safety and meeting a range of key performance criteria such as those specified in AS-22759. VERSIV? PTFE films are used as primary insulation in the miles of wire and cable used in an aircraft offering excellent dielectric properties and resistance to broad temperature ranges (high & low), fire, smoke, and chemicals. ?

Another critical segment for wire and cable is coaxial communication cables that are used within aircraft for signal transmission of data between devices.? The expanded PTFE materials used in coaxial cables offer low dielectric constant allowing for optimal signal transmission at high frequencies. ?

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VERSIV? Extruded PTFE Films are ideally suited for a range of high-performance applications in addition to aerospace wire and cable such as any application where extreme temperature resistance, flexibility and chemically resistant wire is needed. Most importantly these films meet safety standards not evident in alternative technologies.?

Aircraft Safety Pre-PTFE?

To understand the significant part played by PTFE in aircraft, consider the material it has replaced - polyimide. Several issues occurred with polyimide, and the US military, Boeing, as well as NASA, all grounded fleets equipped with the material, when safety red flags, (and high-profile fatal accidents) emerged.?

A key weakness turned out to be polyimide’s insulation properties. It tended to develop circumferential cracks easily, exposing the conductors within. It is also easily degraded by moisture, exacerbating the problem in humid environments or areas of an aircraft subject to moisture, like galleys and lavatories.?

Once the insulation is compromised, arcing can occur, which leads to charring of the polyimide. This changes the insulation’s dielectric properties, turning it into a conductor. In some cases, this led to overloaded circuits not detected by circuit breakers, since the insulation was carrying the excess current rather than the conductor. Other times, the circuit breaker would trip to protect the circuit, but when the crew reset the breaker, the charred insulation would catch fire and burn like a fuse, flames traveling along the wires far from the original arc.?

PTFE-coated films have several advantages over polyimide for use in aircraft applications.?

• Firstly, PTFE can withstand temperatures up to 260°C (500°F), while polyimide can only withstand temperatures up to 200°C (392°F). This makes PTFE more suitable for use in aircraft engines, where high temperatures are common.?
• PTFE is also more resistant to chemical corrosion than polyimide. It is not affected by most chemicals, including aviation fuels, hydraulic fluids, and lubricants. Polyimide, on the other hand, can be damaged by some chemicals commonly found in aircraft.?
• In addition, PTFE, such as found in VERSIV? Extruded Films has a lower coefficient of friction than polyimide, which can help reduce wear and tear on aircraft components. It is also more flexible and has better insulation properties, making it more versatile and easier to work with than polyimide.?