8/20/2019 Polyurethanes are a class of extremely versatile polymers that are made into flexible and rigid foams.doc

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Polyurethanes are a class of extremely versatile polymers that are made into flexible and rigid

foams, fibres, elastomers, and surface coatings. They are formed by reacting an isocyanate (a

compound having the functional group NCO) ith an alcohol (having the functional group O!).

Polyurethane molecules can adopt a linear or a netor" architecture. #inear polyurethanes are

formed by reacting a dialcohol ith a diisocyanate, hereas netor" polyurethanes are formed

from polyfunctional alcohols or isocyanates. $ialcohol monomers include ethylene glycol(!OC!%C!%O!)& diethylene glycol (!OC!%C!%OC!%C!%O!)& ',butanediol

(!OC!%C!%C!%C!%O!)& ',*hexanediol (!O+C!%*O!)& alcoholterminated polyethers

such as polyethylene oxide and polypropylene oxide (see -liphatic polyethers)& and flexible,

alcoholterminated polyesters such as poly',butylene adipate

The alcoholterminated polyethers and polyesters are "non as polyols.

/socyanates commonly used to prepare polyurethanes are toluene diisocyanate (T$/), methylene,0diphenyl diisocyanate (1$/), and a polymeric isocyanate (P1$/). These isocyanates have

the folloingstructures

$uring the late '234s Otto 5ayer, manager of the /6 7arben laboratories in #ever"usen, 6er.,

 prepared many polyurethanes by condensation reaction of dihydric alcohols such as ',

 butanediol ith difunctional diisocyanates. - ma8or brea"through in the commercial application

of polyurethane did not occur until '2', hen a trace of moisture reacted ith isocyanate to

 produce carbon dioxide. The production of this gas resulted in many small empty areas, or cells,

in the product (hich as subse9uently called :imitation ;iss cheese