So, different sorts of plastic usually have different marks on them (the resin identification code, like 1/PET for polyethylene terephthalate etc). However, sometimes one can encounter a piece of plastic (or film; it can be even non-plastic like cellophane) without identification code or whatever sign. What ways to distinguish plastic types can you propose?

It is desirable that these methods can be applied without lab hood and chemical hazard when applied to ordinary types of plastic (at least PET, HDPE, PVC, LDPE, PS, PP, cellophane) unless there's a simple way to eliminate some variants which would cause hazard (like "don't use this for white non-transparent plastics and that otherwise). Ideally this shouldn't require reagents which are hard to accuire but if you have some ideas, throw them anyway.

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    $\begingroup$ FT-IR spectroscopy would be the simplest choice, but probably not what you had in mind. You could make a chart with tests like "reaction to acetone" (crazes, dissolves, nothing), "flame test" (keeps burning, smoke, ...), "mechanical" (breaks, bends, ...). I think you should be able to distinguish most common polymers that way, but there'll certainly be others behaving the same. And many properties vary with processing, additives, etc, so i would not bet on any results from that. $\endgroup$ – Karl Apr 11 '16 at 0:10
  • $\begingroup$ Thanks for this @Karl, I can't "+1" you comment yet, but that's a start. Yeap, I'd prefer to avoid methods requiring set up available in labs only like FT-IR or NMR spectrometers. $\endgroup$ – YakovL Apr 11 '16 at 4:39

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