I'm working on building a high voltage capacitor. I have heard that PET has a very high voltage breakdown. I came across an excellent source of PETG (Polyethylene Terphthalate Glycol). How much will this affect the puncture resistance? I did a bench test that went alright for being in open air. I'm confident it will handle the voltage I need, but I'd still like some solid numbers. Couldn't find any with a google search.
Two vendors claim 16 kV/mm. Should be OK for DC and low frequency AC applications. May need to oil immerse to prevent corona damage especially around the capacitor plate boundaries.
Bert
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Some additional info: Other suppliers quote a lower value (410 V/mil or ~10.4 kV/mm) for Vivak PETG sheet:
So, YMMV.
Using two or more thinner sheets will have a much higher standoff voltage than a single sheet of the same total thickness.
There are so many variables that can affect this. Cleanliness, how oversize you make the dielectric, and the dress of the edges of the plates immediately springs to my mind; I'm sure there are many more that I'm not aware of.
I'd do a hipot test before I put anything into service, and I'd consider doing it regularly if it mattered.
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