Polyurethane, thermoplastic degradation products

An important group of polymers are classified as being thermosetting materials (165) (see Thermosets). The chemistry associated with their formation is often the same as that used for thermoplastic materials, except that in the case of these polymers the monomers used have more than two functions per monomer unit. It is therefore possible to have two materials that ostensibly look chemically similar, but one is a thermoplastic and the other a thermoset. This situation is to be found in Polyurethanes (qv) where, depending on the functionality of the isocyanate or soft block used, the resiJting material may be a thermoplastic or a thermoset. In most cases it is desirable to monitor the cure process to avoid either too slow a formation of the three-dimensional network, and hence poor production efficiency, or too quick a cure with the possibility of excessive exotherms and possible degradation of the material. The formation of a network for a material that has a Tg above... 

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