Polyurea coatings have some unique benefits that have established them far above other types of protective coatings. In this article we are going to examine some of the most important questions that must be answered when considering using polyurea coatings.
What is Polyurea?
Polyurea is an elastomer material procured from step-growth polymerization, which involves combining synthetic resin and reactive isocyanate materials. Thus, the result of an isocyanate part with a resin blend part through the step-growth method of polymerization produces polyurea.
Various formulations of resins and isocyanates can produce the desired setting time, water resistance, pigmentation, flame hindering qualities, and other unique characteristics.
How does Aliphatic Polyurea Differ from Aromatic Polyurea?
Polyureas procured from aromatic diisocyanates are distinguished by ultraviolet (UV) light sensitivity. Sunlight exposure or synthetic UV light can cause degeneration of the polyurea's physical properties and color transformations such as darkening and chalking. Aromatic polyurea is a low-cost option but is not suitable as a top coat; it can be sufficient for a base coat treatment.
Polyureas procured from aliphatic diisocyanates can resist color change due to sunlight exposure and sustain their physical properties even under UV exposure conditions. They are favored for outdoor applications because they can enhance aesthetics with a glossy look and can be utilized at lower film thicknesses of around 30 mils. However, they are costly when compared to aromatic polyureas due to the complex processing required.
What are the Unique Traits of Polyurea?
No coating system can successfully replace polyurea in all regards, due to its novel physical properties and stability. However, it's surface preparation specifications are quite stringent.
Polyurea preserves wooden, concrete, and steel surfaces and structures from abrasion and corrosion damage. It can help preserve a deteriorating concrete structure and help rehabilitation and keep canals sound. It resists scratches, chemicals, oils, and salts in commercial and industrial floor applications. It can also protect boats and other vessels by protecting from cracking and deterioration.
Advantages of polyurea coatings include:
- Quick setting time
- Excellent abrasion and scratch resistance
- Very durable resistance to weather and environmental conditions
- Very beneficial elongation properties
- Can be applied in extreme temperature conditions
- Coating thickness can be finely regulated
- Very effective bonding on correctly prepared surfaces of wood, cement, concrete and metals
- Superior chemical resistance
- Feasibility of low viscosity
- Can be formulated for a very high tensile strength
How does Polyurea Compare to other Epoxies?
Compared to epoxy coatings, polyurea is significantly superior in moisture resistance, UV resistance (for aliphatic coatings), abrasion resistance, chemical resistance, temperature resistance, and durability. It also has a quicker cure time.
Compared to polyurethane, polyurea has superior durability, chemical endurance, and moisture resistance.
What Are Some Notable Applications for Polyurea Coatings?
There is numerous application that benefits from polyurea coatings, including the following:
Automotive industry and material administration
The auto industry has used polyurea coatings for more than thirty years. The coating is popular because of its impact resistance and other mechanical properties.
Polyurea provides abrasion protection in mining and construction equipment, and for lining dump that are used for abrasive materials such as coal and metallic ores. It protects conveyors and waves of conveyor systems that transport abrasive coal, stones, and metallic ores.
It rucis also utilized for bed liners and large commercial vehicles and material handling trucks.
Defense and security sectors
Due to their proven impact resistance, ability to absorb explosive energy, durability and quick setting features, polyurea coatings and linings easily find use in the defense and security sectors.
Polyurea's application in the ballistic missile system is well documented. As a military equipment coating, polyurea can adjust and expand with variations in ambient temperature and form a moisture tight seal. Coatings will be free of marks, dents and abrasion destruction, all while ensuring an attractive glossy appearance. A spray coating of polyurea on truck bed liners can decrease vibration and contribute to safety. Coating military buildings with polyurea can minimize damage due to bomb blasts.
Surfaces of steel and concrete bridges
Polyurea is used for the initial coating and as a repair/maintenance coating because of its fast curing capacity, impact resistance, and elongation and tensile strength. Polyurea’s structure (molecular chain) makes it an elastomer of high durability. This is the secret of its suitability in construction and other fields.
Polyurea coatings can prevent the collapse of concrete structures by effectively repairing a deteriorating portion of the concrete structure and by providing a protective seal around cracking and deteriorating concrete.
What are the Limitations Of Polyurea Coatings?
Polyurea coatings do have some limitations and special considerations.
Because the coating is highly reactive and quick-curing, the setting of the coating without sufficient wetting out time can produce poor adhesion to the substrate. Formulators must ensure total wetting out of the surface before the coating sets. It is a difficult situation.
Aromatic polyurea coatings may react to UV radiation, resulting in color changes and chalking. The aesthetics are negatively affected by UV transmission. For those applications that require a visual appeal, an aliphatic polyurea must be used.
Hot spray applications require specialized and sophisticated spray equipment that are able to produce high pressures and high temperatures. Technicians must be specifically trained for this task.
Formulation, primer selection, and rigorous surface preparation are all critical steps for success.