Polyurethane
Foam
Materials:
- Two flasks of liquid reagents
- Ring stand
and test tube clamp
- Test tubes
- Stirring rod
Procedure:
Equal amounts of the two liquid reagents should be added
to a test tube (both of the reagents together should fill
approximately 1/4 of the test tube). The mixture needs
to be stirred vigorously for 1 to 2 minutes. The mixture
should then begin to grow.
As this reaction proceeds, a fluorocarbon blowing agent is
activated. This blowing agent produces gas bubbles that become
suspended in the silicone surfactant. The bubbles (now trapped
in the polymer) cause the polymer to expand to about thirty
times its original volume. This process produces a very light
and durable solid polymer.
Helpful Hints:
- Be careful not to let the polyfoam drop onto the table
or desk you are working on, it can be very difficult to clean.
- It
may be helpful to compare the degree of cross linking to
the properties of each polymer (the polyfoam is more cross
linked than the slime and silly putty).
- Since the polyfoam
needs time to cure before it should be handled, a previously
prepared sample can be brought with you to pass among the
audience.
- Ask the students to make observations as the reaction
proceed. Ask them if they can imagine any practical
applications for these polymers (such as foam insulation
or sealing cracks.
- The polymer demos are best saved for last
since most students will play with the polymers for a while
after the demo is done.
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