Formation of Polyurethane Foam

Demonstration Experiment on Video

Formation of Polyurethane Foam

Objective: Polyaddition

Peter Keusch

German version

Chemicals:

Desmodur (diisocyanate)

Desmophen (polyhydroxyester)

Glass wares:

beaker 600 mL

2 beakers 100 mL

glass stirring rod

Hazards and safety precautions:

Desmophen is harmful if swallowed.

Desmodur may be harmful by inhalation, ingestion or through skin contact.

Safety glasses and protective gloves must be worn. Good ventilation required.

Experimental procedure:

60 mL Desmodur (diisocyanate) and Desmophen (polyhydroxyester) are poured simultaneously into a beaker. The mixture needs to be stirred thoroughly for approximately two minutes with a glass stirring rod.

Result:

A foam is formed, which will expand to about thirty times its original liquid volume. The beaker will actually get warm - this indicates an exothermic reaction.

Video clip (Download RealPlayer .rm file)

Discussion:

Polyurethane is formed by a polyaddition of diisocyanates and diols. The alcohol component is a polyhydroxyester ·(1)· containing a blowing agent. The diisocyanate component is low molecular.

The blowing agent is solved in the liquid. As the foam hardens the gas is trapped in the cells and small bubbles will be formed throughout the polyurethane product. The finished material is therefore a rigid foam.

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