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Packing Peanuts
Name: Ben C.
Status: student
Age: 20s
Location: N/A
Country: N/A
Date: 2001 - 2002
Question:
This is a chemistry question. When I was a kid I went to
a chemistry camp and the teacher had us dip packing peanuts into
acetone. We dissolved as many as we could into a small cup. Now I am
not sure of the exact process after this, but I think the teacher added
some epoxy and then put two or three drops of another chemical. When
they reacted, the substance began foaming in a large column up out of the
cup. When the reaction was complete, there was a big piece of a
substance that was like Polystyrene foam only it was rock solid! Can anyone
tell me what was going on?
Replies:
Love these puzzler inquiries! This is only a guess based on the assumption
that what you described is complete.
The first step, dissolving the polystyrene in acetone is straight forward.
Polystyrene foam is very soluble in acetone.
Assuming that the only agents added were an epoxy pre-polymer and a few
drops of catalyst, what may have been happening is that the epoxy was a fast
curing type. Epoxy molding resins are available that "cure" in a matter of
minutes, even seconds, and the "few drops" were an appropriate catalyst for
the polymerization of the fast-curing epoxy.
What then happened, I think, is that the heat of the polymerization of the
fast-curing epoxy volatilized the acetone, providing the foaming agent for
the styrene/acetone/epoxy mixture. Because the cured epoxy would be rather
hard the final "product" was an expanded inter-polymer of polystyrene and
polymerized epoxy resin.
Vince Calder
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Update: February 2012
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