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Plastic sulphur

Recently a young lady started working for me as a PhD student, she is working on the radiation processing of waste plastic.

She recently started attending a class which is about polymers, which made me think of a polymer which is unlikely to be on a course on the subject of “useful plastics”. It is important to note that while polymers / plastics are used for lots of useful things in society which you can see such as dustbin sacks, pens, clothing, rope, electrical cables, footballs, floors etc etc there are some polymers which are normally never seen outside the lab.

One of these is plastic sulphur, the method of making it is quite simple and also quite complex at the same time. When sulphur is heated it melts to form a liquid of S8 rings, on heating more it darkens as the rings open. As it heats up the S8 rings form long chains and the mixture becomes very tar like and thick. If it is suddenly cooled by pouring boiling hot sulphur into cold water the chains of sulphur do not have a chance to convert back quickly into S8 rings. The resulting sulphur is soft and rubber like. But on standing it turns back to normal sulphur, the conversion of plastic sulphur back to normal sulphur starts within an hour at room temperature so plastic sulphur can not be used as a replacement for normal rubber.

I made some plastic sulphur a few days ago, a film of this is now on youtube.

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