MadSci Network: Physics

Re: could you please help me with molecule and polymer?

Date: Tue Feb 9 07:49:45 1999
Posted By: Werner Sieber, Research Scientist, Pigment Division, Ciba Specialty Chemicals Corp.
Area of science: Physics
ID: 918143919.Ph

Dear Casey,
Common things like air, water or petrol consist of molecules: If you could 
look at these materials under a magnification of about 10 million times, 
you would see atoms - little balls - stuck together in groups of two, 
three or ten etc., depending on the stuff you look at. Now the molecules 
which make up a POLYMER, like rubber, are special in that they contain 
THOUSANDS of atoms, arranged normally in a linear chain- or thread-like 
configuration. So if you looked at them under a slightly weaker 
magnification, you would see a THICK TANGLE of wiggling spaghetti or a 
felt-like mat of fibres. Because the diameters of these fibres (AND THUS 
THE SPACES BETWEEN THEM) are still of the same order as that of air 
molecules, you can make fairly air-tight balloons from this "felt".
Why should a balloon pop when pricked with a needle? The needle itself only 
makes a tiny hole. Only if the tension in the balloon skin is so high as to 
PROPAGATE THE TEAR made by the needle, the balloon pops. If the needle is 
inserted in such a way as to DISPLACE some "spaghetti" sideways rather than 
to break them, the risk of popping the balloon is much reduced. The thread 
molecules then fit around the needle smugly and even prevent air from 
escaping. I never tried it, but if you take a very sharp needle, maybe 
lubrify it a bit and insert it very slowly into a balloon which is not too 
taut... a bicyle inner tube never pops when pricked with a needle.

Good luck
W. Sieber  

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