How to Identify Different Plastics

This is a fun way I found to determine what type of polymer you're dealing with:

http://www.chymist.com/Polymer%20Identification.pdf

There are more professional ways to determine a structure based on it's properties such as FTIR (Fourier transform infrare spectroscopy), Raman (different type of spectroscopy) and NMR's (nuclear magnetic resonance). With these you can get an accurate definition about the chemical make up of the polymer, and from there, an accurate depiction of what the chemical looks like and is called can be derived.

Outside the lab, not much. Google flame test for plastics.

Due to the number of colors and additives that can be added to thermoplastics, it's impossible to identify them by sight.

Thermosets are more difficult even.

Some thermoplastics are soluble in solvents. Polystyrene, ABS and some types of acrylic are soluble in methyl ethyl ketone or acetone. Nylon is soluble in hexafluoroacetone sesquihydrate. Silicone is mildly soluble in toluene.

Not much help, I know. Others may have more to add.

Burn it the carbon monoxide produced smells like obnoxious.

Have a look at previous threads on CR4 such as the one below.

http://cr4.globalspec.com/thread/49059/How-to-Identify-a-Plastic

Did you have any specific plastics in mind, or was it more of a general, say "how to tell the difference between Nylon and PVC"?

Flame testing to see if you can determine what type of polymer that you have is dangerous and stupid. I know some people do this and take a quick whiff of the smoke and guess what they are smelling. There are so many additives in plastics from static inhibitors, colorants, to UV inhibitors to Fire retardants, anti-static and slipease etc.

It is a chemical soup and should not be ignited to create smoke to sniff. Experts may be able to determine what polymer family but without expensive analysis you may be out of luck.

It is not all bad news. Do some homework. Call resin suppliers and say that you need a suitable polymer to produce the object that you are trying to identify. If they can't help you ask for some recommendations of who could.

Better still try to determine the material by finding out what it is used for and what it will be exposed too. Use a site like Ides Prospector or Matweb to plug in some of the characteristics that you need and see what direction it takes you.

Good luck