Polyurethane was invented by Otto Bayer in 1936.

The product underwent considerable evolution. The first applications were in the field of fibres. This was followed by the successful experimentation of polyurethane foam, at first rigid and later also flexible. Elastomeric polyurethane, as the components developed, was used for the construction of technical articles, wheels, elastic elements of all kinds, scratch proof coating, etc. All these applications involved casting. The expanded forms began to be sprayed in the 1940s, and later the elastomers were also sprayed.

The casting systems use mainly a PREPOLYMER – “A” component (the isocyanate part) and a CURATIVE or REACTING – “B” component.

The various formulas contemplated different ratios between part A and part B. Some formulas have an A to B ratio of 1:1, which is the system used for spraying.

The isocyanate  can be AROMATIC or ALIPHATIC. The aromatic isocyanates are less expensive but they are sensitive to UV rays, and therefore the colours are not fast. The aliphatic isocyanates are stable to UV rays but they are decidedly more expensive.