Which is Best? Epoxy, Polyurea, or Polyurethane Floor Coatings?
Epoxy, polyurea, and polyurethane are great for protecting your floor. They are light reflective, easy to clean, and long lasting. They also have their own advantages depending on the application. So which one should you use and what is the difference?
Epoxy is a thermosetting polymer which is available in three different formulations as floor coating and sealer; water based, solvent based, and 100% solids. These formulations allow for varying degrees of thickness from 3 mils to over 20 mils for a single coating for a garage floor. They also allow for ease of application, special bonding characteristics, and VOC considerations. Epoxy bonds extremely well to properly prepared concrete and can sometimes be used as a resurfacing agent for old or worn concrete that needs a new surface.
The best epoxy formulations are 95-100% solids and provide for an extremely hard, thick, and impact resistant surface. This self-leveling thickness contributes to filling in the small hairline cracks and imperfections of the floor as well as providing protection. It also works well against hot tire pick up, scratching, and wear from abrasion. Epoxy will eventually show some yellowing or “ambering” as the industry calls it when exposed to sunlight for any length of time. A UV inhibitor can be added to slow the ambering process.
Polyurethane is a thermosetting polymer as well and is considered a high performance coating. It is commonly known as “urethane” for short, though that it is technically incorrect and there is actually a big difference between polyurethane and urethane.
Aliphatic polyurethane is the desired choice for most flooring applications. Though they are only approximately 60% to 70% solids depending on the manufacturer, a polyurethane coating is only about 2 to 3 mils in thickness and can’t be adjusted as with epoxy. Aliphatic polyurethane has more flexibility than epoxy and it is this flexibility that aids in absorbing impacts better. It is also much more abrasion resistant. In fact, some manufacturer’s claim that the wear resistance of polyurethane over epoxy is almost 3 to 1. The resistance to chemicals is better than epoxy as well and this includes resistance to solvents such as methylene chloride which is the primary ingredient in paint stripper.
Another advantage of polyurethane over epoxy is that it is U.V. stable. This means that it won’t yellow like epoxy does when exposed to small amounts of sunlight over a period of time. The surface of polyurethane is not as hard as epoxy but it is much more scratch resistant, can tolerate larger temperature swings, and handles humidity much better. It is also available in different finishes from satin to very glossy. Though polyurethane has several advantages over epoxy, it does not bond well to concrete and its thin dry film thickness will not work well as a self-leveling coating to fill in small cracks and divots in the surface. Another consideration is that most polyurethanes are solvent based, meaning they can have high VOC’s. There are good water based polyurethanes which have low VOC’s.
Without getting too technical, Polyurea is a subgroup of polyurethane. It is formed when isocyanates react with water or polyether amines to create a urea linkage. Like epoxy, it is a 2-part component that mixes resin with a catalyst to cause the curing reaction that makes the material hard.
It has low to no VOC’s and has an elongation rate that exceeds 300%, making it much more flexible than epoxy. It is commonly used for spray-on bed liners, interior pipe coating, liquid containment lining and many other industrial applications such as tunnel coatings and fillers for joints. It exhibits excellent wetting characteristics, allowing for good penetration into the concrete for a strong bond.
Polyurea is 100% U.V. stable and will never yellow. It has a crystal clear finish that won’t blush from moisture in the concrete, and has a high abrasion and scratch resistance similar to polyurethane. Polyurea has a high tolerance to heat, meaning hot tire pick up is a non-issue. It also has a high gloss finish with high stain and chemical resistance, and good flexibility for higher impact resistance.
So, which is better for your floor? Epoxy is best used for the base coat on your floor coating, with a polyurethane as a clear coat to protect it. It will help protect the epoxy from yellowing and it will provide for a longer wearing and more scratch resistant surface. Polyurea can also be used as a base coat and a clear coat, with many of the same advantages, but with an added advantage of much shortened installations. Depending on the service needs of your floor, the right chemistry can assure you of many years of durability and beauty.