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Old 3rd March 2004, 07:58 AM   #1
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Exclamation Is plastic film capacitor same as polypropylene ?

Hi,

I was looking for polypropylene capacitors for audio but found only electrolytic , polyester and plastic film available here in Bangalore (India). I was wondering if plastic film is same as polypropylene capacitor.

Thanks in advance
Goldy
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Old 3rd March 2004, 08:14 AM   #2
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There are a number of different kinks of plastic films used in caps; polypropylene, polyester and mylar are a few of them. Where a project calls for plastic film you can use polypropylene.
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Old 3rd March 2004, 08:53 AM   #3
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Default Re: Is plastic film capacitor same as polypropylene ?

Quote:
Originally posted by goldyrathore
Hi,

I was looking for polypropylene capacitors for audio but found only electrolytic , polyester and plastic film available here in Bangalore (India). I was wondering if plastic film is same as polypropylene capacitor.

Thanks in advance
Goldy
No, plastic is just a generic term for any plastic. Most plastic capacitors you wiil be likely to see use a polyester dielectric, since it is the cheapest of the plastics for this purposel. Polypropylene is a specific plastic with excellent properties for audio work, but probably polyester will suffice.

You did not mention the application, but if stability of value were important such as in a radio tuner or a filter, I might suggest polystyrene instead. Teflon will tolerate very high temperatures such as you might find in a tube amp. Each plastic has good and bad properties that make it best for a particular application, but again for general purpose use, polyester will usually suffice.
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Old 3rd March 2004, 08:56 AM   #4
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The name "plastic film cap" is used in general for all caps with some kind of plastic as a dielelectric. You can imagine that various kinds of plastics with different properties can be used. Some of the films have better electrical properties than others and also price is an important factor. The better the film the higher the price. Some films can excel in one area whereas they can be less good than cheaper films in other areas.

Quality ( again: in general for audio ) is in ascending order:

MKT/MKS ( polyester ), MKC ( polycarbonate ), MKP/KP ( polypropylene ), KS ( Styroflex/polystyrene ). PTFE/Teflon is one of the best but hard to find and expensive. There are subvariants like FKP pulse caps which are a polypropylene variant.

MKP, MKC, KS and teflon are harder to find since not all manufacturers produce them. MKT can be found everywhere as it is the least expensive variant. Their specs nearly always surpass the specs of electrolytic caps. Unfortunately not all manufacturers print the series name and /or film type at the cap in question so it can be hard to find out what you can buy. Sometimes they use the MKT, MKP, MKC indication which is fine.

So the caps you can buy in Bangalore ( polyester ) are less good than the required polypropylene types. MKT is sonically not one of the best, polypropylene is better. Buying polypropylene caps does not automatically guarantee good results as different manufacturers produce different qualities/variants. Wima MKP 10 are good allrounders ( but certainly not the best ) and relatively cheap.

I suggest you visit their website for some explanation on dielectric films and their specs:

http://www.wima.de/navig/spotlight.htm

http://www.wima.de/navig/tech.htm
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Old 4th March 2004, 10:47 PM   #5
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Hi Goldi!
Well I think already the most important points have been listed.
Only... where to get in India? !
I know one promising manufacturer called DEKI.
I never tried their capacitors for Audio, but in general
DEKI can deliver polypropylene caps (MKP) in a good quality.
Try: www.dekielectronics.com

Cheers
Markus
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Old 4th March 2004, 11:06 PM   #6
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I use polyester caps in my active xover, and they sound great.
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Old 4th March 2004, 11:06 PM   #7
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AFAIK film means the the conductive layers are deposited on the
plastic dielectric as opposed to using seperate foil conductors.

Most capacitors are film nowadays, foils are bulkier by definition.

Also AFAIK an unspecified film capacitor is Mylar/Polyester.

sreten.
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Old 5th March 2004, 12:30 AM   #8
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polyethylene -- a long chain polymer based upon 2 hydrocarbons. comes in several different varieties, low density, linear low density and high density. your gas tank may be made of high density polyethylene. too bad poor Union Carbide didn't truely appreciate the value of their patent, else they wouldn't have been swallowed by Dow.

polypropylene -- 3 carbons -- replaces jute in carpet backing, makes candy wrappers crackle, excellent for closures etc. and other applications, a very, very handy polymer to have around.

polyethylene terephytalate -- aka polyester -- aka mylar (tm Dupont) -- they stuff they make double-knit suits out of, makes your cotton shirts a little easier to iron.

polycarbonate -- this molecule is based upon "phosgene" of WW-I fame (or infamy for all those correspondents in the Lowlands). GE held a patent for the longest time, trademark is Lexan.
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Old 5th March 2004, 06:42 AM   #9
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Quote:
Originally posted by 5th element
I use polyester caps in my active xover, and they sound great.
That's what you thought till you compared them with something like MKP.
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Old 5th March 2004, 09:50 AM   #10
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Well if you tell me where I can buy MKP's from here without having to go thru masses of farnell web site to find what i want then please do. I wanted to use pollyprops but couldnt find any or if I could they were X series filter caps for mains filtering.
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