Avoid contact with the liquid and vapor of the chemicals in this demonstration.

Chemicals and Solutions: 

100 ml of polyurethane a (toluene diisocyanate plus extras)

136 ml of polyurethane b (gycerol plus extras)


large plastic beaker (2 L capacity)

stirring rod


Mix components a and b in the beaker. Stir until the mixture starts to foam.



The polyurethane forms when an isocyanate group (R-N=C=O) from toluene diisocyante reacts with a hydroxyl group from glycerol forming an ester-like bond.  The reaction can proceed in three directions since all three hydoxyl  groups of the triol can react and both isocyanate groups can react.This leads to a large molecule that is rigidly held into a three dimensional structure.


The foaming is caused by the small amount of water that is present. The water decomposes isocyanate:

R-N=C=O + H2O ---> RNH2 + CO2

To schedule a demonstration, please send an email to the demonstration lab.



Eric Camp

Lecture Demonstration Technician

Bagley Hall 171

(206) 543-1606



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