I tried to do a polymer physics demo with the super-absorbent polymer used in diapers, which should be the sodium salt of poly acrylic acid!?
However, the "Poly(acrylic acid sodium salt), average Mw ~5,100 by GPC, powder" that I ordered from Sigma (http://www.sigmaaldrich.com/catalog/product/aldrich/447013) does not seem to absorb water well.
What is the problem? Why does it not absorb nearly as much as the powder I took out of a diaper? Is it a matter of molecular weight, or physical form / cross linking / crystallinity?
Any help would be appreciated!
Thanks,
Jan
The linear homopolymer is probably not superabsorbent. I suspect you need a copolymer to reduce crystallinity and some crosslinking to product a gel.
https://en.wikipedia.org/wiki/Superabsorbent_polymer
In our company we use a super-absorbent polymer from DEFOTEC which is called DEFOSORB CA 50. We produce a special coating for our composite round profiles (endless fibre reinforced duroplastics) for strength elements in cables with "Super Water Blocking". The head of R&D at DEFOTEC is Dr. Richard Mertens, phone: +49 2151 1546027 E-Mail: [email protected] Website:
http://www.defotec.de/en/industries/cable-industry.html
You must be able to buy a suitable gel from gardening shops which will perform. These are cross linked at an appropriate density and swell but do not dissolve. They are also adjusted to pH 7.
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