Manufactured through the reaction of glycol and an isocyanate, polyurethane is an organic compound with particularly good moisture- and corrosion-resistance characteristics. Polyurethane sealant is useful in both industrial and commercial applications. Additionally, polyurethane is often used as a heavy-duty adhesive, as well as a coating.

A polyurethane sealant may be pressed, layered, sprayed, or brushed onto joints, but the most common method of application is with a caulk gun. Most sealants are sold in 10-ounce (295.74 ml) tubes that will fit the common caulking gun.

As well as being resistant to moisture, chemicals, and corrosion, polyurethane sealant is noted for its flexibility. A common problem with joints is the expansion and contraction of the joint. Polyurethane, with its inherent resiliency, is particularly resistant to cracking due to movement of the joint materials.

These sealants are available as either one- or two-component compounds. Since the typical residential user is typically looking for one that is easy to use, the basic residential product has only one component. This means there is no need to mix ingredients before they can be used.

The typical polyurethane sealant is hydrocarbon-based. With the advances in water-based polyurethane technology, however, effective water-based, or latex, sealants and coatings are now available. These products are noted for their low-odor, low-variable organic compound (VOC) content, and ease of application and cleanup.

In addition to producing an excellent sealing compound, polyurethane is often used as a wood coating. The same factors that make it a good sealant contribute to its effectiveness as a coating. Polyurethane’s resistance to abrasion, its scuff resistance, makes the product a superior wood-floor coating.

A quality sealant will adhere to masonry, wood, concrete, steel, aluminum, vinyl, and most plastics. Its flexible, yet durable finish not only protects these vulnerable materials, but, when used as a coating, provides a gleaming, blemish-free finish, as well. Obviously, proper application methods must be used to achieve the desired results. Polyurethane coatings work especially well as an anti-corrosive on metal products. Some experts even recommend using it over powder coating for protecting metal, though a textured finish, which many people require, is difficult to achieve.