Polyester or Polypropyolene. Which is which?

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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.
 

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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.
 
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.
 
Another”trick” is to visit the manufacturer’s website.
Thanks stinius. Last year I waited out bad traffic by harvesting dozens of what looks like the TS05N from a 20 year old Mitel SX200 switch destined for the trash. The size strongly suggested polyester but I always wondered if that 'nude' construction was still in use.
An interesting note about the spec sheets is DF appears to be more related to construction than dielectric. The TS05N exceeds the performance of at least two of the latter. Or the sheets are b0rked.
 
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