Re: Suitable capacitor dialectrics

["Bert Hickman" <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Tesla list wrote:
> 
> Original poster: "Metlicka Marc" <mystuffs-at-orwell-dot-net>
> 
> hello bert,
> i was wondering what exactly happens to polystyrene in oil? i've had the
> cup cap soaking for some time now and checked it after your post, it
> doesn't seem mushy or anything?
> marc

Marc,

Well, my notes indicated that (supposedly!) polystyrene either degraded
or dissolved in mineral oil, and that it had poor chemical resistance.
Unfortunately, my notes do not indicate the original source of the
information, - I suspect it may have come out of one of the many books
on plastics I rented from the local library a couple of years back. 

However, after seeing your post, I did a bit more digging and found that
other (web-based) polymers references seem to indicate that polystyrene
suffers no damage after 30 days immersion and that it has excellent
resistance/no attack by mineral oils (as long as they have no aromatic
or alaphatic solvent content). However, polystyrene is significantly
more brittle than polyethylene or polypropylene, and may be more prone
to cracking under applied stress. 

Your mileage may vary, but if your cup caps seem to be working OK, go
for it! :^)

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-com
Web Site: http://www.teslamania-dot-com