How can I identify the major chemical component in vintage hard plastic? Styrene, acetate, or butyrate?

Question

I collect and restore specific vintage plastic dolls from the late 1940's through the 1950's. I have determined that though they look alike they were produced using one of 3 different chemicals: styrene, acetate, or butyrate, at different times.

The plastic with the butyrate is breaking down causing an acidic reaction on some, I can identify it once it starts to break down from the "sour milk" odor. The acetate I believe, gives off a "vinegar" type odor as it breaks down. I don't know anything about the styrene.

Does anyone know of a way to identify the chemical in the plastic, preferably BEFORE it starts to break down? (I have determined that water seems to be the agent that starts the breakdown process in most cases.)

Any suggestions about how to identify the chemicals and possibly how to arrest the progress of the breakdown(and mask the odor) of the chemicals would be greatly appreciated! Resources to locate the information would also be helpful!

Thanks!

Answer 1

You can research the types a bit better to find out if you can tell easily.  If you took off a chip and ran an infrared spectrum, or did a reflectance IR spectrum, you could tell, but I have a feeling you want something easier than that.   Since they probably all have pigments it will be hard to tell by looking.  

But to prevent the breakdown is a more practical question.  The breakdown is from hydrolysis of the bonds in the polymer, regenerating monomers.  Keeping them cool will help a lot, slowing the reaction.  Also, keeping them in a low humidity environment.  That could be as easy as sealing them up, on a dry day, in plastic and including some of those little silica gel packets you find in some products (labeled "do not eat").  Those will work best if you let them sit in an oven on 'warm' (110-120C, 230-250F) to dry them out for a few hours before using them.   It could be as drastic as storing them under dry nitrogen that you can buy, and which would have the added advantage of limiting oxidation by oxygen in the air.