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Re: Polyethylene Capacitors

Tesla List wrote:
> 
> > Subject: Polyethylene Capacitors
> 
> >From gowin-at-epic-1.nwscc.sea06.navy.milWed Sep 18 23:53:15 1996
> Date: Wed, 18 Sep 1996 12:54:10 -0500
> From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
> To: tesla-at-pupman-dot-com
> Subject: Re: Polyethylene Capacitors
> 
> Tesla List wrote:
> >
> > >From gowin-at-epic-1.nwscc.sea06.navy.milTue Sep 17 22:37:24 1996
> > Date: Tue, 17 Sep 1996 16:50:54 -0500
> > From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
> > To: tesla-at-pupman-dot-com
> > Subject: Polyethylene Capacitors
> >
> > All,
> >         I`m about to build my first set of Polyethylene/Oil
> > Capacitors. I've already downloaded the construction tips by
> > Richard Quick and I've found them to be very complete. I've
> > also purchased some 14"x50' aluminum flashing and 3-(6"x19") PVC
> > pipe with caps for containers. The one question I have is,
> > why should I special order some 30 mil polyethylene ( stacked
> > 3 sheets for 90 mil thickness)? When 15 sheets of 6 mil polyethylene
> > will do just the same. And is readily available at a department
> > store.
> >
> > Big Red, HV Capacitors. Burn Baby Burn.
> > ITS Member
> > D. Gowin
> 
> Gentlemen,
>         There has got to be a better alternative to using 30 mil or
> 60 mil LDPE. Even the HDPE is very expensive. I've just spent my
> lunch hour calling around to the local Indiana plastics suppliers.
> Bloomington, Indianapolis, Cincinatti and even someplace near St. Louis.
> The prices were very high. A single sheet of 48"x96" LDPE 30 mil
> averaged around $18 a sheet! The 60 mil averaged $34 a sheet. A
> sheet of HDPE 48"x96" 60 mil was $43.96.
> 
>         Please would somebody answer my question regarding 6 mil
> thickness LDPE stacked for 90 mil thickness. Will this work and
> are there any pitfalls?
> 
>         Stacked plates of plexiglass in large square plastic comforter
> boxes are looking better every day. According to my calculations,
> 16 - 14"x14" sheets of aluminum flashing using 17 - 16"x16" 3/16"
> thick plexiglass will yeild .01 uF. With a Tesla voltage rating of
> 32 KV. The mineral oil I've found was realitively inexpensive,
> $9 per gallon.
> 
> Any comments are more than welcome.
> 
> Big Red, HV Capacitors. Burn Baby Burn.
> ITS Member
> D. Gowin

Dan,

Certain plastics are attacked or weakenned by prolonged exposure to
mineral or transformer oil. LDPE, HDPE, Nylon, PVC, Delrin (Acetyl), PP
(Polyproylene) are all OK or show only slight swelling. Others will show
moderate attack and limited life: Polycarbonate (Lexan), PMMA
(Plexiglas), and polystyrene fall into this category. When I was looking
for a suitable container for my cap, I saw LOTS of potential containers
that, unfortunately, were polycarbonate and not compatable with
transformer/mineral oil.  Check for the recycling markings on the bottom
of the product first.  

For the same reason, Plexiglas plates may not have a long service life.
Although the dielectric constant is good (3.1), the dissipation factor
for PMMA is about 8 times higher than for Mylar (40x10-3 vs 5X10-3 at 1
MHz), and abot 200 times worse than LDPE. Stick with LDPE, HDPE, or PP
for your plates for longer operational life.

Safe (and non-leaky) coilin' to ya!  :^)


-- Bert --