What Is Polyurethane Coating?

Wood and metal finishes are commonly coated with polyurethane.

Polyurethane was invented during World War II as an alternative to rubber. After the war, hundreds of applications for this material were developed for industrial uses and consumer products. Protective polyurethane coatings are one common example.

Composition

Polyurethane is made of highly elastic organic polymers, or chains of molecules that are primarily composed of carbon and hydrogen derived from fossil fuels. Once the polyurethane has set, it can be soft and rubbery or extremely hard and resilient. Although many polyurethane applications are sold ready to be applied, some are activated by a catalyst, such as an epoxy.

Applications

At the consumer level, polyurethane coatings are frequently used as a protective coating. A polyurethane coating forms a durable surface with an impermeable seal from the environment, protecting the substrate from physical damage or corrosion caused by oxidation or humidity. Polyurethane can be used to coat and protect many materials including wood, metal, and plastic. Typical examples include automotive paint finishes and furniture varnish.

Advantages

Polyurethane coatings are easy to apply because they do not require a primer, and they set between a few minutes or a few hours. They offer fantastic protection from normal wear and often improve a material's cosmetic appearance. Polyurethane coatings pose fewer risks than many alternatives because they do not release vapors that are harmful to humans or the environment.

References

• Engineer's Handbook: Surface Finishing Coatings
• Center for the Polyurethanes Industry: Learning Center -- Polyurethane