Everything about Kapton totally explained
Kapton is a
polyimide film developed by
DuPont which can remain stable in a wide range of temperatures, from -269 °C to +400 °C (4 K - 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 H and HN is poly(4,4'-oxydiphenylene-pyromellitimide). It is produced from a
diamine and
pyromellitic acid by a
condensation reaction producing water as byproduct. 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).
Kapton insulated wiring has been widely used in civil and military
avionics (electrical wiring for aircraft) because of its very light weight compared to other insulator types as well as good insulating and temperature characteristics. However it was soon 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.
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.
(External Link
)" 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 (J. L. Wright,
Space Sailing, Gordon and Breach, 1992).
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 as well as its high transmittance to x-rays make it the preferred material. It also doesn't suffer from
radiation damage. Another prominent material for these purposes is
beryllium.
The thermal conductivity of Kapton in temperatures from 0.5 to 5 Kelvins is rather high κ = 4.638×10
−3 T0.5678 W·m
-1·K.
This together with its good dielectric qualities and its availability as thin sheets have made it a favorite material in
cryogenics (devices working in temperatures down to
absolute zero, -273 °C or 0 K).
Kapton is also regularly used as an insulator in ultra-high vacuum environments as it has a low
outgassing rate.
Further Information
Get more info on 'Kapton'.
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