Polyurethane coatings for concrete: new developments offer VOC compliance, performance versatility.

POLYURETHANE COATINGS are widely used in nearly every application known to the coatings industry. They protect and beautify all types of structures and products, ranging from steel bridges and wooden furniture to metal and plastic automotive components. For some 30 years, these coatings have been synonymous with top-of-the-line technology for their ability to provide high-performance properties for diverse end uses.

Included among the wide range of suitable applications for polyurethane coatings are concrete surfaces. The versatility of polyurethane coatings chemistry results in the availability of aromatic and aliphatic polyisocyanates and other raw materials that allows polyurethane formulations to be virtually tailor-made for concrete.

Of critical importance due to current environmental considerations, polyurethane coatings for concrete are available in solvent-borne, water-borne and solvent-free formulations to meet both existing and proposed regulations for VOC emissions. In fact, polyurethane coatings are capable of achieving the ultimate goal for low VOCs: 0.0 pounds per gallon.

Protecting concrete

Concrete is a versatile construction material. It, however, has several shortcomings.

For example, concrete is an alkaline substance and, as such, it not only is highly susceptible to chemical attack, it is extremely sensitive to alkyd-based paints.

Concrete also is a porous substance, which means that potentially damaging agents can more readily penetrate it, increasing the likelihood and extent of damage. Finally, concrete has relatively poor abrasion resistance and cohesive strength.

These inadequacies can contribute to physical deterioration, cause cleaning to be difficult and, ultimately, lead to breakdown or failure of the material.

Of course, concrete can be protected. Its shortcomings can be reduced, and years can be added to its service life by protecting it with a suitable coating. There are many types of coatings available for concrete. None, however, are as versatile as polyurethane coating systems.

Chemistry: foundation of polyurethane versatility

To help formulators meet specific end-use requirements, it may be useful to review the fundamental details of polyurethane coatings chemistry and capabilities.

Polyurethane coatings can be …