Polyester or Polypropyolene. Which is which?

Black Gate · 19th September 2009, 03:48 PM

I have a quantity of the caps shown in the photo below. Some are polyester and some are polypropylene but I cannot remember which is which.

Caps numbered 1, 4 and 5 look like polypropylenes, with the rest being polyester.

Can someone confirm this or correct me?

How does one differentiate the two types of caps?

Many thanks.

Black Gate · 20th September 2009, 11:58 PM

No answers? Was this a stupid question?

jackinnj · 21st September 2009, 01:15 AM

Quote:

Originally Posted by Black Gate

No answers? Was this a stupid question?

No, it isn't a stupid question. You'll need a really great impedance meter like an HP or Gen Rad to measure both the impedance and dissipation factor.

BrianDonegan · 21st September 2009, 01:52 AM

You can make some educated guesses...

Polyprop caps are generally larger for a given value. For example, the 2.2uF is definitely a polyester cap.

Black Gate · 21st September 2009, 07:49 AM

Oh well, thanks anyway guys. Cheers!

hasaudio.co.nz · 21st September 2009, 08:16 AM

Yea I dont think you can really tell from the outside. As Jack said you need a descent Impedence meter to determine that.

Damon Hill · 4th October 2009, 05:41 AM

The quick and dirty test I use for capacitors is to charge the unit to, say 10 volts, then short the terminals for several seconds, wait a minute and then measure the remaining voltage with a high-impedance voltmeter. Polypropylenes will have a significantly lower residual voltage, though measuring lower-capacitance units gets tricky.

analog_sa · 4th October 2009, 06:04 AM

Quote:

Originally Posted by Black Gate

No answers? Was this a stupid question?

This has been discussed before and is really fast and simple. Polyester has a positive tempco and polyprop negative. Use a hair dryer and capacitance meter and you'll have the answer in seconds.

SY · 4th October 2009, 12:16 PM

Quote:

Originally Posted by analog_sa

This has been discussed before and is really fast and simple. Polyester has a positive tempco and polyprop negative. Use a hair dryer and capacitance meter and you'll have the answer in seconds.

Nice trick, I didn't know that! My method, much less elegant, is to destroy one, unwind a bit, then ignite with a cigarette lighter. PP smells like a burning candle, PE smells slightly sweetish.

MJL21193 · 4th October 2009, 12:20 PM

My trick is to not worry about it.

21st September 2009, 08:16 AM	#6
hasaudio.co.nz diyAudio Member Join Date: Aug 2009	Yea I dont think you can really tell from the outside. As Jack said you need a descent Impedence meter to determine that. __________________ Hasaudio Speaker Components

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20th September 2009, 11:58 PM	#2
Black Gate diyAudio Member Join Date: Aug 2009 Location: Adelaide	No answers? Was this a stupid question?

21st September 2009, 01:52 AM	#4
BrianDonegan diyAudio Member Join Date: Dec 2004 Location: Rock Ridge	You can make some educated guesses... Polyprop caps are generally larger for a given value. For example, the 2.2uF is definitely a polyester cap.

21st September 2009, 07:49 AM	#5
Black Gate diyAudio Member Join Date: Aug 2009 Location: Adelaide	Oh well, thanks anyway guys. Cheers!

4th October 2009, 05:41 AM	#7
Damon Hill diyAudio Member Join Date: Mar 2001 Location: Auburn, WA (somewhere between Seattle and Tacoma) Blog Entries: 1	The quick and dirty test I use for capacitors is to charge the unit to, say 10 volts, then short the terminals for several seconds, wait a minute and then measure the remaining voltage with a high-impedance voltmeter. Polypropylenes will have a significantly lower residual voltage, though measuring lower-capacitance units gets tricky.

4th October 2009, 12:20 PM	#10
MJL21193 Account disabled at member's request Join Date: Mar 2007	My trick is to not worry about it.

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