Definition - What does Polyurethane Coating mean?
A polyurethane coating is a polyurethane layer applied to the surface of a substrate for the purpose of protecting it. These coatings help protect substrates from various types of defects such as corrosion, weathering, abrasion and other deteriorating processes.
Polyurethane itself is a type of polymer that is connected to a chemical compound group known as carbamates. This polymer material is also thermosetting in nature; in other words, it burns rather than melts when heated. Another characteristic of polyurethane coatings is its customizability. These coatings can be formulated to be glossy, muted, opaque or transparent.
While polyurethane coatings may appear to be visually similar to other coatings (e.g., epoxy), they possess several distinct properties that make them ideal for specific situations.
- While polyurethane coatings are relatively durable, they are softer and more elastic than their epoxy counterparts. This attribute makes polyurethane-coated floors ideal for moderate to heavy pedestrian traffic. The reduced stiffness gives polyurethane floors a slight springiness, allowing them to absorb sharp impact loading.
- This durability also makes them more resistant to abrasion and less prone to dents and scratches.
- Improved elasticity also means that polyurethane floors are able to maintain their shape and mechanical properties in temperatures lower than 30°F (-1°C).
Corrosionpedia explains Polyurethane Coating
The characteristics and properties of polyurethane floor coatings make them ideal for numerous applications, including airports, hospitals, car parks, freezing chambers, malls and other busy commercial areas. Specially formulated water-based polyurethane coatings are also non-flammable. This characteristic allows them to be used in environments where combustion is likely to occur.
Many polyurethane coatings require no additional processing to cure. They are simply applied and cure upon exposure to moisture in the air. They can be sprayed or rolled onto a base material.
Polyurethane coatings are used for many different applications, including wood floors, metals and on top of other coatings.
Comparing Polyurethane Coatings with Epoxy Coatings
One of the significant advantages of a polyurethane coating is its relatively fast cure time compared to an epoxy coating. Floors coated with polyurethane can be ready for operation in a little as 24 hours without any additional processing. Epoxy coatings, on the other hand, need a curing time of at least seven days before they are ready for use.
Epoxy coatings are more resistant to a wide range of aggressive chemicals such as sulfuric acid. However, polyurethane coatings exhibit superior resistance to lactic acids, making them ideal for floor coatings in industries that process dairy products.
Polyurethane coatings are also known for their ability to adhere well to a wide variety of substrates in a broad range of temperatures.
Some Shortcoming of Polyurethane Coatings
While polyurethane coatings are ideal for numerous applications, they are not a one-size-fits-all solution. One of the main shortcomings of this coating material is its sensitivity to moisture. When moisture attacks polyurethane-coated floors, bubbles can form, leaving unsightly stains and imperfections on the surface. Due to this weakness, polyurethane coatings are unsuitable for areas with high levels of moisture or humidity.
Polyurethane also has a limited pot life, i.e., the coating remains viscous for a limited time, after which it is no longer usable. As such, the mixed coating must be appropriately handled by well-trained and knowledgeable staff.
Ultraviolet light can also cause this coating material to break down and degrade. Therefore, care must be taken to limit its exposure to direct UV light sources.