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Re: Saran Wrap as a Dielectric
Tesla list wrote:
>
> Original poster: MaverickIce00-at-aol-dot-com
>
> List,
>
> I recently noticed that a roll of Saran Wrap I have is Polyethylene. It's
> probably only a few microns thick (can't find the caliper) but if I used
> enough layers, would it make a suitable dielectric for a capacitor? Would it
> be as good a dielectric as factory-manufactured LDPE? I checked it out, and
> it seems to be pretty clean, no chemicals or anything, but since this is not
> made for such a duty, would it be a bad idea to go ahead and make a cap with
> it? Thanks for your help.
>
> - Joshua
Joshua and all,
Common Dow Saran Wrap is not polyethylene, nor is it polyester. It's
actually polyvinylidene chloride (PVDC), or an alloy of PVDC and
Polyvinyl Chloride (PVC), and is a member of the PVC family of polymers.
Unfortunately, if you thought PVC was lossy, PVDC is even 5-10X lossier!
Don't bother using this stuff as a capacitor dielectric for RF use -
it'll act more like a resistor! Use plain old Low Density Polyethylene
dropcloth or polypropylene sheet protects instead... or make an MMC from
PP caps.
PVDC's electrical characteristics (along with many other useful
polymers) can be found at:
http://members.tm-dot-net/lapointe/Plastics.htm
LDPE PP PVC PVDC
==== == === ====
Dielectric Strength (V/mil):
0.001" Material 5000 8000 - -
0.005" Material 3000 2700 - -
Dielectric Constant:
1 kHz 2.2 2.2 3.0 3.9
1 MHz 2.2 2.2 2.7 3.0
Dissipation Factor:
1 kHz 0.0003 0.0003 0.009 0.052
1 MHz 0.0003 0.0003 0.006 0.050
Safe cappin' to you!
-- Bert --
--
Bert Hickman
Stoneridge Engineering
Email: bert.hickman-at-aquila-dot-com
Web Site: http://www.teslamania-dot-com