Self life of electrically charged film of electert condenser microphone

Instead of external phantom high voltage, modern small electret capsule use already charged film for the polarization. As it's electrostatic charge, in normal life we get many static charged objects due to the friction and it will lose after some conditions. What about the self life of these small electret condenser microphone? I am sure they will survive decades but do they lost their charge gradually and lost performance gradually too? (I have heard early electret mic used to stop working after few years because of charge lost.)

It should be virtually infinite.

An electret is created by subjecting a suitable type of molten plastic to a high voltage field and then cooling it so it solidifies, still the field.
The electric charge is "set in" to the material itself, rather than just being a surface effect that can dissipate, as with a static charge on normal objects.


edit- that should have said "so it solidifies, still in the field."

rjenkinsgb said:

It should be virtually infinite.

An electret is created by subjecting a suitable type of molten plastic to a high voltage field and then cooling it so it solidifies, still the field.
The electric charge is "set in" to the material itself, rather than just being a surface effect that can dissipate, as with a static charge on normal objects.

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Wut. I didn't know you could do that with a plastic. Crazy.

dknguyen said:

Wut. I didn't know you could do that with a plastic. Crazy.

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No more crazy than a permanent magnet.

gophert said:

No more crazy than a permanent magnet.

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That's steel though.

dknguyen said:

That's steel though.

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I'm sorry, I thought you were fascinated by a permanent electrostatic field, which in my mind is just a parallel to a permanent magnetic field.

Also, steel is magnetic but doesn't make a very good (strong/long lasting) permanent magnet.
See AlNiCo, Ferrites, NbFeB as better examples.