Superabsorbent Polymer,
Sodium polyacrylate
• It is a polymer where the long
chains are cross-linked to one
another.
• It is a polymer that can absorb
water many times its volume
therefore earning the term
superabsorbent.
• After it absorbs the water it
forms a stiff gel.
Why sodium polyacrylate
absorbs water
• It is a long chained molecule with
many repeating units (a polymer).
• Each of the repeating units has a
portion that holds an electrical
charge.
• The electric charges on the
polymer attract water molecules
and bind them to the polymer.
• Each charge binds several water
molecules and each molecule of
polymer can bind a large volume
of water.
Procedure
• Remove cotton-like filling from
diaper
• tear filling into small pieces and
put in the plastic bag
• rub bag in hands to separate the
polyacrylate from the cotton
• put the polyacrylate in a dry
beaker removing any visible
cotton
• slowly add liquid into beaker
stopping to make sure it is
absorbed, continue adding liquid
until no more is being absorbed
• measure the volume of liquid
absorbed
Questions
• Why does something dissolved
in the water reduce the amount
of water absorbed by the
polymer?
• What are some uses of this
material?
Why the salt decreases the
amount of water absorbed
• Like the polymer the salt also
contains electrical charges
which attract water molecules.
• Furthermore, the charges in the
salt are attracted to the charged
parts of the polymer and
displace the molecules of water
from the polymer.
Other uses of sodium
polyacrylate
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filtering fuels
food packaging
potting soil
alkaline batteries
hair gels
fire retardants