Commercial applications began later in 1952 and grew steadily as polyurethane foams became a viable choice for rigid foam buns and molding parts where the reaction occurred in the mold for the finished part. The advantages of polyurethane foam (PUF) helped grow many applications and uses. High heat resistance and long-term stability due to the polymer being a thermoset plastic led to the development of PUF adhesives in roofing applications.
Polyurethane is a reaction polymer, where isocyanates react with polyols and result in a thermosetting polymer. The main feature of thermosetting polymers is that they do not melt or breakdown with the application of heat. For example, when eggs and flour are combined and cooked, a pancake is made. The pancake cannot be returned to eggs and flour by heating it up. The opposite of thermoset polymers is thermoplastic polymers. Thermoplastic polymers will return to their original state if heated. As an example of this, an ice cube will become water if it is heated. However, if the water is returned to a freezer, it will become an ice cube again.
The other benefit of thermosetting polymers is the long-term stability of the polymer. However, the stability of polyurethane polymers is mainly susceptible to exposure of ultraviolet (UV) light. When PUF is exposed to sunlight, which contains UV light, there is a yellowing discoloration that occurs over time. The higher energy of UV light can also cause reactions that break-up the PUF and flake the exposed foam off as exposure time is prolonged. Read More.