Lab11 - How can we characterize the absorption capacity of...

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How can we characterize the “absorption capacity” of a superabsorbent polymer? Introduction Superabsorbent polymers are substances that can absorb and retain extremely large amounts of a liquid relative to their own mass. In particular, a class of polymers called crosslinked polyacrylates are excellent water absorbing products. They are extensively used in personal disposable hygiene products such as baby diapers and sanitary napkins. Other applications include horticultural water retention, control of spill and waste aqueous fluids, humidity control, blocking water penetration in underground power or communications cables, water-blocking tape, artificial snow for motion pictures, and even as fire retardants. Superabsorbent polyacrylate molecules are not simply linear. Their long chains are covalently tied together in many places by cross-links made from organic molecules known as alkenes . The strong covalent bonds of these cross-links are responsible for holding the molecule together when the polymer is placed in water. In the absorption process, water solvates or surrounds the three dimensional polymer. The resulting solution of positive and negative ions has some unique features. All of the negative charges remain attached to the polymer backbone. Attracted by these negative charges, the positively charged sodium ions (Na+) are trapped inside the polymer network as well. When the polymer is in contact with water, water molecules can travel in and out of the polymeric network. Given the higher concentration of water molecules in the exterior of the polymer, more of them are likely to go in than to come out until the internal pressure is large enough to establish equilibrium (equal number of particles going in an out of the polymeric network). Challenge
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This note was uploaded on 12/08/2009 for the course CHEM 151 taught by Professor Staff during the Fall '08 term at Arizona.

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Lab11 - How can we characterize the absorption capacity of...

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