Re: Polypropylene (fwd)

---------- Forwarded message ----------
Date: Thu, 23 Jul 1998 23:33:19 -0500
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Polypropylene (fwd)

Tesla List wrote:
> ---------- Forwarded message ----------
> Date: Thu, 23 Jul 1998 16:24:08 +-100
> From: "Gregory R. Hunter" <ghunter-at-enterprise-dot-net>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Polypropylene
> Can anybody give me data on polypropylene film?  I saw a flat plate cap at
> the UK Teslathon that appeared to be made of plastic document protectors &
> foil.  I found some pocket-style document protectors at work and examined
> them.  The recycling symbol says they are polypropylene.  I can't find any
> values as to dielectric strength, dielectric constant, etc., in my
> literature.
> Also, does anyone know the meanings of the various plastics recycling
> symbols?  For example, I know "HDPE 2" is polyethylene, but I'm wondering
> what the shorthand is for various other plastics.
> Cheers,
> Greg


For the most part polypropylene (PP) and polyethylene (PE) have very
similar properties. PP tends to be a bit "stiffer", which can be a
problem with rolled caps using thicker sheets. While the actual
dielectric constant is around 2.2 - 2.3, the "practical" value for
homemade capacitor calculations is about 2.0 due to unavoiable space
between the plates and the dielectric material. Dielectric strength is a
function of the thickness of the material - use multiple thicknesses of
thinner material for best results. 

Re: Shorthand Notation:

   Number  Shorthand        Material
     #1      PET    PolyEthylene Terephthalate
     #2     HDPE    High Density PolyEthylene 
     #3      PVC    PolyVinyl Chloride
     #4     LDPE    Low Density PolyEthylene
     #5      PP     PolyPropylene
     #6      PS     PolyStyrene
     #7             Other...

-- Bert --