What is a spray polyurethane/polyurea elastomer?

Spray polyurethane and polyurea elastomers are coatings that mimic the tough and flexible quality of natural rubber, but are, created by the reaction of liquid resins. These resins are kept separated until just before they are mixed and sprayed. Typically they react together quickly enough that they can be rapidly over-coated multiple times to build thicknesses of several millimeters (or even inches) on a vertical surface without sagging or dripping. Polyurethane elastomers are based on the reaction of poly-hydroxyl-containing resins with polyisocyanates. Polyurea elastomers are the reaction product of poly-amine resins with polyisocyanates. These resins can also be combined to form a hybrid technology in a way to optimize their individual advantages.

Spray applied elastomeric coating technology was established in the market in the late 1980s. They evolved from the adaptation of flexible amine crosslinkers for use with epoxy systems, when they were used to crosslink aromatic polyisocyanates. These were the first spray polyurea coatings. This combination of resins is very reactive, even curing while sprayed upon a block of ice. Many new methods of formulating these systems have been developed since then, but all are essentially based on aromatic polyisocyanates and hence not light stable. More recent systems use hydroxyl containing resins (polyols) in combination with amines to create polyurea/polyurethane hybrids. This modification now allows a wide variety of coating hardnesses, cure speeds, and chemical resistances to be obtained.