Kapton is a polyimide film developed by DuPont that remains stable across a wide range of temperatures, from −269 to +400 °C (−452 – 752 °F / 4 – 673 K). Kapton is used in, among other things, flexible printed circuits (flexible electronics) and thermal micrometeoroid garments (the outside layer of space suits).
The chemical name for Kapton K and HN is poly(4,4'-oxydiphenylene-pyromellitimide). It is produced from the condensation of pyromellitic dianhydride and 4,4'-oxydiphenylamine. Kapton synthesis is an example of the use of a dianhydride in step polymerization. The intermediate polymer, known as a "poly(amic acid)," is soluble because of strong hydrogen bonds to the polar solvents usually employed in the reaction. The ring closure is carried out at high temperatures (200–300 °C, 473–573 K).
The thermal conductivity of Kapton at temperatures from 0.5 to 5 kelvins is rather high for such low temperatures, κ = 4.638×10−3 T0.5678 W·m−1·K−1. This, together with its good dielectric qualities and its availability as thin sheets have made it a favorite material in cryogenics, as it provides electrical insulation at low thermal gradients. Kapton is regularly used as an insulator in ultra-high vacuum environments due to its low outgassing rate.
Kapton-insulated electrical wiring has been widely used in civil and military aircraft because it is lighter than other insulators and has good insulating and temperature characteristics. For these reasons, the sunshield of the James Webb Space Telescope will be made of it.
However, Kapton insulation ages poorly: an FAA study shows degradation in under 100 hours in a hot, humid environment. It was found to have very poor resistance to mechanical wear, mainly abrasion within cable harnesses due to aircraft movement. Many aircraft models have had to undergo extensive rewiring modifications--sometimes completely replacing all the Kapton-insulated wiring--because of short circuits caused by the faulty insulation.
The descent stage of the Apollo Lunar Module, and the bottom of the ascent stage surrounding the ascent engine, were covered in blankets of aluminized Kapton foil to provide thermal insulation. During the return journey from the Moon, Apollo 11 astronaut Neil Armstrong commented that during the launch of the Lunar Module ascent stage, he could see "Kapton and other parts on the LM staging scattering all around the area for great distances." 
According to a NASA internal report, space shuttle "wires were coated with an insulator known as Kapton that tended to break down over time, causing short circuits and, potentially, fires." The NASA Jet Propulsion Laboratory has considered Kapton as a good plastic support for solar sails because of its long duration in the space environment.
Kapton is also commonly used as a material for windows of all kinds at X-ray sources (synchrotron beam-lines and X-ray tubes) and X-ray detectors. Its high mechanical and thermal stability and high transmittance to X-rays make it the preferred material. It is also relatively insensitive to radiation damage. Another prominent material for these purposes is beryllium.
Because Kapton adheres so well to ABS and thereby prevents ABS parts from warping, it is commonly used in 3D printers for covering the surface of a heated build platform.
Kapton is a registered trademark of E. I. du Pont de Nemours And Company.
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