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[Seany]

OK.. Me has been naughty and I have just stuck a plastic pen (a normal biro pen) into a candle. It caught fire in about 5 seconds, as well as melting, and it gave off some white smoke. It caught a massive fire so I started shaking it around, and it gave off sparks and things.. Me got all worried and it started smelling bad. Eventually, I stopped the fire.. And I looked at the pen and it was black and blue (the plastic was black and blue) and it was all melted and it looked demented!

I then stuck the pen into a piece of paper and pulled it out.. And it stuck to the paper, but a loooooong thread of blue plastic thin thing kept stretching. Just like when you eat cheese on a pizza, it just keeps going and going and going. The pen did that as well! And the little thread of plastic was over 1.5m long!! It was hard though, like nylon. It was very interesting.

Anyway, I got alot of mess around the table with the plastic, so I got some tissue and rubbed it off (didn't have my parents permission!), but it smells a bit in the room.

What is that smell exactly, and is it harmful? Like carbon monoxide or something? I have heard that the fumes from plastic is bad, but why and what is it?

[Seany]

I really sometimes don't understand what you are saying..

[another_someone]

There are lots of different plastics, and they will give off lots of different vapours when they decompose.

It could be just a simple hydrocarbon, or it could contain cyanides, or PCB's, or lots of other substances.  Without knowing what the plastic was (including what additives might have been incorporated), it would be difficult to know what are the likely volatiles it would create.

It is unlikely that the small amount you have breathed in would have done you harm, but volatiles given off from plastics in house fires are a major cause of death.

[Seany]

There are lots of different plastics, and they will give off lots of different vapours when they decompose.

It could be just a simple hydrocarbon, or it could contain cyanides, or PCB's, or lots of other substances.  Without knowing what the plastic was (including what additives might have been incorporated), it would be difficult to know what are the likely volatiles it would create.

It is unlikely that the small amount you have breathed in would have done you harm, but volatiles given off from plastics in house fires are a major cause of death.

Hmm.. What made my see-through bit of the pen go black though? It rubbed off with a tissue, but there were black chalk like things around it

[eric l]

I remember that in my student days we had a "flame test" for identifying different plastics.  I can't find it back anywhere, and I remember only part of it. 
The whole idea was to cut off a small part of the plastic - I remember it said "the size of a fingernail clipping" - and hold it in the flame of a cigarette lighter.
Then we had to answer different questions like :

• does it burn or melt - or both or neither ? (neither would have been PTFE, PF or UF)
• does it go on burning out of the flame ?
• what is the smell like ?
• what is the smoke like ?
• can you pull a thread from the melting plastic ?

The test not only gave us a way to identify the plastic, it also taught us a lot about its properties and workability.

From your description I would think the plastic was polystyrene (I suppose it was a cheap pen).  Did it produce a sweet smell while burning/melting ?  (would be an indication of styrene).  If that is the case the smoke is toxic indeed.  (check wikipedia for styrene : http://en.wikipedia.org/wiki/Styrene - the article also gives a link to the safety data sheet (MSDS).

And next time, use a small piece of plastic, like the size of a fingernail clipping (or maybe try the same thing with a fingernail clipping and compare it to some plastics)