Polyurethane Volcano
SCIENTIFIC
Introduction
Construct a model volcano using polyurethane foam.
Concepts
•Polymers
•Catalysis
Materials
Polyurethane Foam System (Part A, 20 mL and Part B, 20 mL)
Cups, disposable plastic, clear, 10-oz, 3
Clay
Demonstration tray
Food coloring, red, green and blue
Party hat, large (cone-shaped)
Aluminum foil, Al, 16″ × 16″
Scissors, heavy-duty or utility knife
Beaker, borosilicate, 300-mL
Wooden splint
Safety Precautions
Perform this reaction in a well-ventilated lab or an operating fume hood. Parts A and B of polyurethane foam system may contain skin
and body tissue irritants. Avoid breathing any vapors produced and avoid skin contact. Do not touch the polyurethane foam until it has
completely hardened. Wear chemical splash goggles, chemical-resistant gloves, and a chemical-resistant apron. Follow all laboratory
safety guidelines and wash hands thoroughly with soap and water before leaving the laboratory.
Procedure
1. Take a large, marble-sized piece of clay and roll it out into a thin rope.
2. Place the thin clay rope around the bottom edge of a 10-ounce plastic cup.
3. Place the cup upside down on the table and carefully press a 16″ × 16″ piece of aluminum foil on the bottom of the cup
with the clay. Make sure to center the foil (see Figure 1).
4. Invert the cup with the foil and place it into a wide, cone-shape mold, large enough to fit the cup. A party hat works
well. The opening of the cup should be level with opening of the large cone (see Figure 2).
5. Place the cone into a 300-mL beaker to hold the party hat steady.
6. Press the aluminum foil firmly against the walls of the hat (see Figure 2).
Clay
7. In a fume hood or well-ventilated area, pour approximately 20 mL of liquid
Part A into a disposable plastic cup. Note: The exact volume is not critical. Do
not use glassware! It is impossible to remove the hardened foam. Please use
only disposable materials for the handling and mixing of polyurethane foam.
8. Place approximately 20 mL of liquid Part B in a second disposable cup. Note:
The volume of Part B should be equal to that of Part A.
9. In the cup containing Part A, add 1 drop each of red, green and blue food
dye. Stir the mixture with a wooden splint until the color is uniform. The
color will be dark reddish brown.
Foil
Cup
Figure 1.
Foil
Pour
polyurethane
foam mixture
10. Pour the contents from cup B into Part A. Mix well—the liquids will
begin to react.
11. As the liquids react, pour the mixture between the plastic cup and the foil
of the cone-shaped mold. Carefully distribute the reacting polyurethane
foam around the cup to create a level volcano (see Figure 3).
12. Allow the polyurethane foam to completely react. It will become hot.
© 2016 Flinn Scientific, Inc. All Rights Reserved.
Party hat
(cone-shaped mold)
Figure 2.
Publication No. 11052
061616
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Polyurethane Volcano continued
Caution: Do not touch the foam until it hardens.
Cup bottom
13. Once the foam has fully reacted and has cooled down (approx. 10–15 minutes), remove the mold and the aluminum foil from the polyurethane foam
(see Figure 3).
Hardened
polyurethane
foam
14. If desired, remove the clay from the edge of the cup from the Procedure,
step 2.
Disposal
Opening for rubber tubing
Please consult your current Flinn Scientific Catalog/Reference Manual for general
Figure 3.
guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The disposable cups, aluminum foil and party hat may be thrown in the trash. Any leftover liquids should be mixed together, allowed to react, and then the solidified polymer may be disposed of in the trash according to Flinn Suggested Disposal Method #26a.
Connecting to the National Standards
This laboratory activity relates to the following National Science Education Standards (1996):
Unifying Concepts and Processes: Grades K–12
Evidence, models, and explanation
Constancy, change, and measurement
Content Standards: Grades 5–8
Content Standard B: Physical Science, properties and changes of properties in matter, motions and forces, transfer of
energy
Content Standards: Grades 9–12
Content Standard B: Physical Science, structure of atoms, structure and properties of matter, chemical reactions,
motions
and forces, conservation of energy and increase in disorder, interactions of energy and matter
Tips
• Acetone may be used to remove any hardened polymer on the table.
• You can construct a party hat out of construction paper.
• Do not touch the foam as it reacts. It will take about 15 minutes for the surface to firmly set and may contain unreacted material for up to 24 hours. Some people will have allergic reactions to unreacted monomers.
• The polymer foam “mountain” may be used as a prop for a foaming reaction, such as the decomposition of 6% hydrogen peroxide using yeast catalyst. Cut a hole in the bottom of the cup (top of the volcano) and place the mountain over an Erlenmeyer flask for the decomposition reaction.
Discussion
The mountain is constructed with polyurethane foam. There are many forms of polyurethane such as fibers, coatings, elastomers, flexible foams, and rigid foams. The foam in this system is a rigid foam that is used in furniture, insulation, flotation
devices, and many other items. The rigid polyurethane foam is produced by mixing equal parts of two liquids, called Part A and
Part B. This lightweight foam expands to about thirty times its original liquid volume and will become rigid in about five minutes.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.
Polyurethane Volcano continued
Part A is a viscous cream-colored liquid containing a polyether polyol, a silicone surfactant, and a catalyst. The polyether polyol
contains reactive hydroxyl (–OH) end groups. The silicone surfactant reduces the surface tension between the liquids. The catalyst is a tertiary amine which aids in speeding up the reaction without being chemically changed itself. Part B is a dark brown
viscous liquid containing diisocyanate and higher oligomers (dimers, trimers or tetramers).
When the polyether polyol (Part A) is mixed with the diisocyanate (Part B), an exothermic polymerization reaction occurs, producing polyurethane (see Equation 1).
H O
O H
Equation 1
HO R OH + O C N R′ N C O ➞ O R O C N R′ N C n
Polyether polyol
Diisocyanate
Polyurethane
During the course of the polymerization reaction, a small amount of water reacts with some of the diisocyanate. A decomposition reaction occurs and produces carbon dioxide gas, thus causing the solution to foam and expand in volume. Pores in the
mixture are created from the gas; these pores are visible when looking at the rigid substance. The multifunctionality of both
reactants leads to a high degree of crosslinking in the polymer, causing it to become rigid within minutes (see Equation 2).
H O
H
H
O H
O C N R′ N C O + H2O
H N R′ N H + CO2(g) Equation 2
HO C N R′ N C OH
Diisocyanate
Water
References
Rosato, D. V. Rosato’s Plastics Encyclopedia and Dictionary; Hanser: New York, 1993; pp 318–320, 572.
Shakhashiri, B. Z. Chemical Demonstrations: A Handbook for Teachers in Chemistry; University of Wisconsin: Madison; 1983; Vol.
1, p 77.
Materials for the Polyurethane Volcano are available from Flinn Scientific, Inc.
Catalog No.
C0335
A0009
V0003
Description
Polyurethane Foam System
Acetone
Vegetable Dyes (food coloring), Set/4
Consult your Flinn Scientific Catalog/Reference Manual for current prices.
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© 2016 Flinn Scientific, Inc. All Rights Reserved.