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Polystyrene and oil?
I have got 2 sheets 2 x 1 meters of Polystyrene (PS), 0.5mm (0.02") thick.
Dielectric constant: 2.5
Dissipation factor (-at- 1MHz): 0.0003
Dielectric strength (0.2 mm thickness): >40 kV/mm (i.e. >1016 kV/mil)
Water absorption: <0.1%
So I believed that was a feasible material for my capacitors until some of you
mentioned that it cannot stand oil. A call to the manufacturer confirmed it:
they
spoke about it standing 4 hours, maximum one week.
>From the web I found a table about PS were it was possible to see that PS
stands
SOME oils but not ALL oils. So I tested two samples of PS:
A - clear PS, 0.25 mm thick
B - white PS, 0.5 mm thick (the one for the capacitors)
I used olive (!) oil and motor oil (full synthetic). I haven't got yet
transformer oil!
Several days at 20C degrees didn't change a thing in the samples. Then I put
the samples
in motor oil to bake into my furnace for 5 hours at 75C degrees. The B
(white) sample
didn't show any visible change. The A (clear) sample lost its transparency,
became opaque.
With the aid of a microscope I saw on the B sample a lot of microscares:
still the sample is
as flexible as it was before, and the scares aren't deep.
I have read that silicon oil is used fro transformers and that it doesn't
attack most of
plactics.
Do you know what is the oil you use for your capacitors ?
Has anybody used PS in rolled capacitors ?
________________________________________________________________________
Marco Denicolai Vista Communication Instruments, Inc.
Hardware Development Manager www.vistacom.fi
marco-at-vistacom.fi Kaisaniemenkatu 13 A
fax: +358-9-622-5610 SF-00100 HELSINKI
phone: +358-9-622-623-15 Finland
Remember, Murphy was an optimist! I am not...
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