1-17
Extruded Polytetrafluoroethylene
Extruded polytetrafluoroethylene is a high-temperature insulation used extensively in aircraft and
equipment installations. It will not burn, but will vaporize when subjected to intense heat. Conductors for
high temperatures use a nickel coating rather than tin or silver to prevent oxidation. Nickel-coated wire is
more difficult to solder, but makes satisfactory connections with proper soldering techniques.
WARNING
Avoid breathing the vapors from extruded polytetrafluoroethylene insulation
when it is heated. Symptoms of overexposure are dizziness or headaches. These
symptoms disappear upon exposure to fresh air.
Q24.
What safety precaution should you take when working with extruded polytetrafluoroethylene
insulated wiring?
Fluorinated Ethylene Propylene (FEP)
FEP has properties similar to extruded polytetrafluoroethylene, but will melt at soldering
temperatures. It is rated at 200º C and is, therefore, considered a high-temperature insulation. There are no
known toxic vapors from FEP. Common-sense practice, however, requires that you provide adequate
ventilation during any soldering operation.
Asbestos
Asbestos insulation was used extensively in the past for high-temperature insulation. Today, it is
seldom used by the Navy. Many naval ships and aircraft, however, still contain asbestos-insulated wiring.
Aboard ship, this is particularly true in galley and laundry equipment. The reason for discontinuing the
use of asbestos as an insulator is that breathing asbestos fibers can produce severe lung damage. It can
render you disabled or cause fatal fibrosis of the lungs. Asbestos is also a factor in the development of
cancer in the gastrointestinal tract. Safety precautions concerning asbestos will be covered in more detail
at the end of chapter 3.
WARNING
Avoid inhalation of asbestos fibers. Asbestos fibers have been found to cause
severe lung damage (asbestosis) and cancer of the gastrointestinal tract. Follow
Navy safety precautions when working with all asbestos products.
One type of asbestos-covered wire is shown in figure 1-9. It consists of stranded copper conductors
covered with felted asbestos. The wire is, in turn, covered with asbestos braid. This type of wire is used in
motion-picture projectors, arc lamps, spotlights, heating element leads, and so forth.
Figure 1-9.—Asbestos Insulation.
