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Asked by SilentSwiftwave to Laura on 7 Nov 2014. This question was also asked by Zoe, chris, ScienceMad123.
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Laura Schofield answered on 7 Nov 2014:
Excellent question! You are a scientist already! A true scientist will always ask questions if they don’t know the answer which is exactly what you’ve just done!
There is a chemical in fruit peel (mainly oranges, lemons and other citrus fruits) called citric acid. This has lots of carbon, oxygen and hydrogen on it and is quite a big molecule. But by breaking some bonds and removing carbon dioxide, we can get to methacrylic acid. Next I add on one more carbon (a methyl group) and hey presto I’ve got the building blocks for perspex (the most common plastic in the UK!)
In order to actually do that, I work with water at high temperatures (as lots of energy is needed to break bonds) and pressure (to make sure the water stays as a liquid and doesn’t boil) and look at my results using something called nuclear magnetic resonance spectroscopy (it is very complicated but tells you what bonds you have in your molecule).
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Comments
SilentSwiftwave commented on :
Wow that is very cool!
Would this method of making plastic be earth freindly meaning that the plastic could just decompose into the ground. If so thus method should be used to make every type of plastic + this would also cut down on our fossil fuels usage. This would be amazing and you would automatically win ny vote!
Laura commented on :
I like to think so too! Unfortunately at the moment it isn’t biodegradable but that is the next step that we want to look at. There are more and more people working on biodegradable plastics though and one of the top ones at the moment is made from cellulose that makes up cell walls in plants!
Joe commented on :
If the Perspex was biodegradable, would it still be Perspex?
Laura commented on :
Strictly speaking no it wouldn’t be. Perspex is a trade name for a specific plastic, poly(methyl methacrylate) to be precise! To make it biodegradable, we would have to alter the structure of it so it wouldn’t be poly(methyl methacrylate) any more but it means it could get a new, cooler name!
Joe commented on :
How efficient is this method? Is the Perspex the same quality as regular Perspex?
Laura commented on :
Hi Joe. It’s a pretty good process as it has a 50% yield (so for every 2 molecules of citric acid, you get one molecule of the precursor for the plastic). But any unreacted citric acid can be recycled and put back through the reactor.
I actually have a couple pieces of Perspex in my flat, one made by the normal process and one made by my process. I have to keep them in labelled bags because I cannot tell the difference otherwise! They are completely identical!