Is plastic film capacitor same as polypropylene ?

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goldyrathore

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#1
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
 
#3
goldyrathore said:
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
Click to expand...

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.
 
#4
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
 
#7
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.
 
#8
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.
 
#10
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.
 
#11
5th element said:
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.
Click to expand...

JMO but I've read in several books polycarbonate should
be used for active filters. In audio circuits I've found them
to be better (slightly cleaner) than polyester and its not
difficult to source reasonable sized values.

For higher values I use a polycarbonate in parallel with a polyester.

🙂 sreten.
 
#13
5th element said:
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.
Click to expand...


How do you think I find them ? They don't come walking to me, it takes some effort. Try some websites of cap manufacturers like Wima and search for their MKP series and note down the name of that series. Now search on the Farnell website for that series or just the word MKP. The smartest method is using the manufacturers partnumber ( if available ) and search for that at Farnells. It will lead you directly to what you want.

Just the word MKP gives this result:

http://international1.farnell.com/Search/search4-frame.jhtml?_requestid=88189

They stock Teflon too etc. I see that the UK pages are a lot less helpful than the dutch version. Search for the numbers on the dutch pages and order in the UK I would say.
 
#14
OK so if I am to spend lots of time finding the right caps what exactly am I after?

I tried searching at farnell here for wima, which turned up about 150 results but no MKP parts, MKP got me 2 listed parts.

Clicking on the link provided turned up zero results to I researched for MKP and got a few results 15 I think of vishay MKP types, which has a couple of useful vaules but thats about it.

I tried to find a supplier for Wima here and got nothing good. All the places were wholesale companies and dont supply to the public, or alteast thats how it seems. When you click on the capacitors section of thier products and all it has it makes and links to the makes hmm anyway, I dont think its going to be easy.

Out of interest where do you buy all of your Wimas from Jean-Pual?
 
#17
You thought wrong then. Possibly some brands MKC might be better than another brands MKP's but in general MKP is the better one ( technically and sonically ). BTW MKC is harder to find, for me anyhow. It seems that MKT and MKP are the ones that stay around.

OK so if I am to spend lots of time finding the right caps what exactly am I after?
Click to expand...

MKP or polypropylene of some brand with a wellknown name/reputation and let your ears be the judge. Sorry for the link that does not work ( anymore ). It worked when I posted it. Just click on the dutch flag and do a search there. Farnell has MKP of Evox-Rifa and they're OK too. Found several useful values on the dutch site.
 
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