ID this plastic

rwm

rwm

Robert
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I have a piece of black plastic that I have labeled as ABS. It machines a lot like polypropylene and I suspect a mix up. How can I tell these materials apart? I plan to glue it to another piece of ABS so that will fail if it is polypropylene. Is there a burning test? Solvent test?
Robert
 
Since the plan it to glue it why not just give that a try. There are so many different plastics that I doubt you'll be able to accurately ID it and it really doesn't matter if it works for your application.

This of course assumes you're not building a critical part in which case it makes sense to just buy what you need with a traceable source.

JMHO,

John
 
Also, PP seems to melt and flow together while ABS will soften but doesn't really melt.

I would suggest building up a library of known plastics for comparisons to unknowns. Many of the plastic parts have recycle info on them. Others can be identified knowing the source.

There are literally thousands of polymer and copolymer formulations. It would be impossible to identify a plastic uniquely but it is usually good enough to know the plastic family.
 
Very helpful RJ.
So I doused both pieces with acetone and then tried burning them as you describe....
No really:
I wiped the surface with acetone with no effect at all. A known piece of ABS readily came off on the rag. This material is actually PP!
Now I need to have a long talk with the stock manager who labeled this.
Robert
 
rwm said:
Very helpful RJ.
So I doused both pieces with acetone and then tried burning them as you describe....
No really:
I wiped the surface with acetone with no effect at all. A known piece of ABS readily came off on the rag. This material is actually PP!
Now I need to have a long talk with the stock manager who labeled this.
Robert
Click to expand...
Acetal (Delrin) isn't attacked by acetone either. but it has an eye stinging smoke when hit with a flame or hot iron.
 
Good to know! It is definitely PP since I have only purchased PP and ABS sheet. I have some Acetal rod and that machines very differently.
Robert
 
I use the lick test. If it tastes like Cherry/Almond, it's PP. If it tastes like dog excrement, it's ABS.
Let me know when you've completed the test....
:p
 
GunsOfNavarone said:
I use the lick test. If it tastes like Cherry/Almond, it's PP. If it tastes like dog excrement, it's ABS.
Let me know when you've completed the test....
:p
Click to expand...
I could not tell if you were serious or kidding but I said, what the heck. German chemists used to taste all unknown chemicals and record the result. I chewed on a little piece of each one. The PP really had no perceptible taste. The ABS tastes a little "chemical"? Hard to describe, but I think you could tell them apart this way Especially if you were a sommelier...
Robert
 
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