Polyurea Coatings and Their Uses
Polyurea was developed by NASA as a replacement for the gel coatings applied to the inner sections of the space shuttles. These gels had to be thick enough to prevent heat damage and thick enough to allow for a strong seal. Unfortunately, these gels tended to deteriorate once they dried so NASA scientists experimented with polyurea to produce an extremely stiff but durable protective layer against heat, pressure and radiation. Polyurea can also be mixed with silicone so that it can replace the need for a thick and potentially damaging gel coat on the outer surface of the vehicle. The material proved to be ten times tougher than traditional gel coatings and it also had the added benefit of providing greater flexibility.
Polyurea has come on leaps and bounds since its inception. Gels and other sealing applications can degrade over time due to weathering, exposure to the sun, and the process of aging. Polyurea has an incredible ability to maintain its structural integrity and functionality as well as resist corrosion. It has the unique ability to quickly set under specific temperature and weather conditions so that the coating is able to remain rigid while providing moisture resistance. Polyurea can withstand extreme temperatures up to 500 degrees Fahrenheit so it is perfect for use in heat-sensitive electronics and tools.
Although polyurea is commonly used in manufacturing, it is also found in the automotive industry as well as in the aerospace and construction industries. Many manufacturers prefer polyurea over other alternatives because of its extreme physical properties which include high density, low tensile strength, low moisture resistance, and its ability to bond with almost any surface preparation including metal, ceramic, fiberglass, resins, and thermoset materials. Some manufacturers may use a combination of polyurea/silicone coatings as a method of achieving a high physical property and long lasting performance.
Polyurea is made through several distinct processes. The most common and efficient way of manufacture is by injection molding. Polyureas are molded as part of the molds using a hardening agent such as calcium hydroxide, silica, magnesium, or silicon. This hardening agent is added to the polyurea at a ratio based on the specific need and size of the mold cavity. The second method of manufacture is called flash drying. Heat is used to rapidly evaporate the moisture from the polyurea in the form of gas.
The third method of manufacture uses thermal roll forming. Polyurea coated metal surfaces are heated to approximately 1700 F and the coating is then applied. The heated coating is allowed to cool and harden so that the polyurea coating is applied as quickly as possible to the metal parts or assemblies that will be coated. The fourth method is called gas tumbling. A fine mist of nitrogen is sprayed onto the polyurea coating to harden it, and then the resulting material is applied to the metal parts or assemblies.
Polyurea coatings are available for a variety of purposes. For example, polyurea can be used in the automotive, transportation, and marine industries, for impact resistance, flame retardant properties, and as moisture barrier for various applications. These polyurea coatings can also be used in the plating process for vehicles. For this reason, polyurea coatings are becoming more popular for use in many new building constructions and renovation projects.
