Toying Around with Chemistry
 
 

Polyurethane

Polyurethane is prepared by a reaction between a diol and a diisocyanate.  One major use of polyurethane is in the stretchable spandex fibers used for bathing suits and leotards.  These polyurethanes have a fairly low degree of cross-linking so that the resultant polymer is soft and elastic.  A second major use of polyurethanes is in the foams used for insulation and toys like the Nerf ball.  Foaming occurs when a small amount of water is added during polymerization, giving a carbamic acid intermediate that spontaneously loses bubbles of CO₂. 

Polyurethane foams are generally made using a polyalcohol rather than a diol as the monomer so that the polymer has a high amount of three-dimensional cross-linking.  The result is a rigid but very light foam suitable for use as thermal insulation in building construction and portable ice chests.