Re: LDPE oil tolerance?

To: tesla-at-poodle.pupman-dot-com
Subject: Re: LDPE oil tolerance?
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 30 May 1997 08:57:00 -0500
Approved: tesla-at-stic-dot-net
Subject:      Re: LDPE oil tolerance?
       Date:  Fri, 30 May 1997 07:48:37 +1200
       From:  "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
         To: tesla-at-pupman-dot-com


Hi Steve,

>   From:  Steve Falco <sfalco-at-worldnet.att-dot-net>
>     To:  tesla-at-pupman-dot-com
> 
> 
> I recently repaired a dead neon by the usual freeze and chip techniques
> mentioned on this list.  The short was between the side of one secondary
> winding and the steel core.  I removed the mica/paper insulation, which
> was charred, and decided to embalm the unit in oil to provide new
> insulation.
> 
> I placed the unit in a Rubbermaid container which is made of
> polypropylene (PP) with an LDPE cover.  I then filled it with mineral
> oil.  After a week or two, the PP was fine, but the LDPE cover had
> warped and swelled badly.  I wound up discarding it.
> 
> I guess I am concluding that PP is more oil-tolerant than LDPE, yet we
> prefer LDPE for oil-filled capacitors for its dielectric properties.

Well I use LDPE simply because it is reasonably cheap and easily 
obtainable. I would *much* prefer to use PP if I knew where to get it.
LDPE swells by about 10% in most oils in my experience. 
 
Malcolm

> My first question is:  Any comments on long-term effects of oil on LDPE
> in capacitors?
> 
> My second question is:  Assuming I have my heart set on oil-filling my
> transformers, what would be a suitable container?  (I'd also like to
> build a bigger capacitor, and was thinking of the Rubbermaid trash
> pails, but now I am afraid they will not hold up to the oil.)
> 
> I suppose a metal box is a possibility, but that would be hard to
> fabricate.  Anyone tried a plastic picnic cooler?  Not sure what they
> are made of...
> 
>         Steve Falco
>         Morris Plains, NJ
>         sfalco-at-worldnet.att-dot-net
> 
>