PolyurethaneFoam

=**__Polyurethane Foam__** =

//__ Materials: __//

 * Polyurethane foam system
 * o Liquid A (polyether polyol, silicone surfactant, catalyst)
 * o Liquid B (diisocyanate)
 * Disposable Cups
 * Stirring rods
 * Paper Towels
 * 20oz. Bottle (or similar)
 * Vegetable Dyes
 * Acetone (for removal)

//__Procedure:__//

 * 1) If desired, place several drops of food coloring to one of the cups and stir thoroughly to mix.
 * 2) Spread a paper towel or newspaper flat on the table and place one of the cups in the center of the paper towel.
 * 3) Pout the contents of the Second cup into the cup on the paper towel and stir thoroughly until you see the foam beginning to expand. Remove the stirring rod.
 * 4) Observe the foam as it expands to about 30 times its original volume. The cup will get warm, indicating an exothermic reaction. Do not touch the foam until it is completely hardened.


 * 1) In a fume hood or a well ventilated area, pour approx. 20mL of liquid part A into a disposable cup. //Note:// The exact volume is not critical. Add A few drops of food coloring, if desired, and stir.
 * 2) Place approximately 20mL of liquid part B into a second disposable cup. //Note:// The volume of Part B should be approx. equal to that of Part A.

Explanation:
Upon mixing, a polymerization reaction occurs in three directions leading to a large molecule that is rigidly held into a three-dimensional structure. At the same time, the small amount of water present causes a decomposition of some of the isocyanate and the evolution of carbon dioxide which results in the foaming. The freon, which boils at 23.7°C (75°F), is vaporized by the heat of the reaction and also contributes to the foaming. The carbon dioxide and Freon bubbles create pores in the viscous mixture as the foam sets into a rigid mass. The cell size and structure of the foam is controlled by the silicone surfactant.  __Freon: __ Liquid Refrigerant  __Isocyanate: __ any compound containing the univalent group –NCO  __Surfactant: __ any substance that when dissolved in water or an aqueous solution reduces its surface tension or the interfacial tension between it and another liquid.

Chemical Equations:
Polyether Polyol + Diisocyanate --> Polyurethane Diisocyanate + Water --> Compound + Carbon Dioxide Gas (Foaminess)

Common Uses:
· Low-density flexible foam used in upholstery, bedding, and automotive and truck seating · Low-density rigid foam used for thermal insulation and Resin Transfer Molding cores · Soft solid elastomers used for gel pads and print rollers · Low density elastomers used in footwear · Hard solid plastics used as electronic instrument bezels and structural parts · Flexible plastics used as straps and bands · Microcellular foam seals and gaskets · Durable elastomeric wheels and tires, automotive suspension bushings · Electrical potting compounds · High performance adhesives and sealants · Spandex fibers · Carpet underlay · Hard plastic parts (such as for electronic instruments) · Some surfboards are made with a rigid polyurethane core

Works Cited:

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 * Flinn Scientific Instruction Set