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Re: silicone rubber as dielectric in caps
From: Jim Lux[SMTP:jimlux-at-earthlink-dot-net]
Sent: Sunday, November 30, 1997 3:38 PM
To: Tesla List
Subject: silicone rubber as dielectric in caps
> The newer flyback transformers are potted in some kind of silicon
> rubber. If a vacuum pump were available thin it might make a very nice
dry
> capacitor. Some of the plastics dealers sell silicon rubber in two part
> cans that cure upon mixing. If the mixture were poured over a flat plate
> capacitor and then pumped on to remove air bubbles the corona from the
> resulting capacitor should be very minimal. The unknown is whether
silicon
> rubber can conduct heat away sufficiently to prevent the capacitor from
> overheating. The cure time for thick molds is also a problem as the full
> dielectric strength is unavailable until fully cured. Anybody tried
this?
I've molded quite a few things with various urethanes and silicones and the
technique of pulling a vacuum on it to get the bubbles out is pretty
standard, particularly when you want a very clear casting, say of acrylic
or polyester. You should be able to get a very low viscosity 2 part
silicone with good electrical characteristics without too much trouble
(call your local GE rep or check the web, trade name is RTV). Cure times
for the ones with good electrical characteristics tends to be in the 24
hour range, which is also long enough to get the bubbles out.