Superabsorbent Polymer, Sodium polyacrylate

1
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.

2
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.

3
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

4
Questions

• Why does something dissolved in the water reduce
  the amount of water absorbed by the polymer?
• What are some uses of this material?

5
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.

6
Other uses of sodium polyacrylate

• filtering fuels
• food packaging
• potting soil
• alkaline batteries
• hair gels
• fire retardants