Under certain conditions, yes, polyurea can potentially crack. This is because polyurea is a thermoplastic material, like many other protective coatings and liners. It can become brittle and eventually crack when exposed to a sudden or excessive temperature change of more than 40°F (22°C). This cracking typically occurs in two ways – crazing or micro-fracturing.
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Crazing refers to the formation of small cracks in the surface of the coating due to shrinkage after application. Micro-fracturing involves deeper cracks caused by increased coating stress due to the expansion or contraction of substrate materials beneath it.
The best way to prevent polyurea coatings from cracking is to prepare them carefully before application and properly cure afterward. For example, make sure that all surfaces are clear from dirt, dust, grease, oil stains, etc., before applying the coating, as these can cause adhesion failure, which could lead to cracking down the line. Also, be aware that some substrates are prone to absorption when wetted: if dampness has occurred from snow melt or rainfall, for example, then additional time should be taken for adequate drying before application so as not to risk shrinkage during cure time later on, which could again result in craze cracking over time. Finally, ensure that you follow your manufacturer’s instructions and adhere strictly to their recommended drying times for optimal performance; any deviations here will also strain your polyurea.
Polyurea is an incredibly versatile coating material with numerous commercial, industrial, and residential applications. It is best known for its exceptional waterproofing capabilities, extreme durability and flexibility, and fast drying time.
But as with any roof coating technology, polyurea has its share of drawbacks. When determining the suitability of a polyurea-based coating system, it is essential to know its strengths as well as its weaknesses.
In this guide, we take an in-depth look at this remarkable and multifaceted coating material.
Polyurea is an elastomer consisting of isocyanate (A-component) and synthetic resin (B-component). This type of “reaction” product is created via a process known as step-growth polymerization.
The isocyanate and resin components can be formulated to improve specific physical properties, such as dry time, moisture resistance, flame retardants, pigmentation, and other qualities.
Polyurea was introduced in the late s, so it is a relatively newer roof coating technology. Early material formulations were especially hard, offering little to no elongation or elasticity. Over time, its elongation was improved, thus opening the door to numerous other applications (more on this below).
Recommended reading: For an in-depth look at the various types of roof coating chemistries, click here.
Polyurea is available in two varieties: aliphatic and aromatic.
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Aliphatic polyurea is best suited for top-coat applications as it offers superior UV resistance and color stability. It costs more than the aromatic variety (nearly twice as much) but requires less material to achieve the desired film thickness during application.
Aromatic polyurea is primarily used as a base coat due to its lack of UV stability. It will gradually break down, discolor, and chalk if exposed to the sun’s UV rays; therefore, it must be top coated to ensure performance.
The material cost for a polyurea roof coating system ranges from $1.25 to $1.75 per sq. ft. Overall costs (including installation) will vary based on the size/complexity of the roof, condition of the existing substrate, material thickness, choice of top coat, building location, warranty requirements, etc.
Polyurea is slightly more expensive than some alternative roof coating systems (see chart below).
Most polyurea roofing systems are warranted to last anywhere from 10 to 15 years. However, they can easily last up to 25 years or more with proper installation and routine maintenance.
Moreover, a polyurea roofing system’s elastomeric top coat (typically silicone or acrylic) can be recoated numerous times throughout its lifespan to help increase longevity and ensure performance.
Polyurea is spray-applied on surfaces using highly-specialized, plural-component spray equipment.
The isocyanate and resin components that makeup polyurea are shipped to job sites in 55-gallon drums. The materials are transferred into separate tanks within a spray rig apparatus and heated to an appropriate temperature. The unit then pressurizes and pumps each component through heated hoses to a spray gun at a specific ratio (usually 1:1).
As the isocyanate and resin are dispersed, they react to produce the polyurea membrane, which is typically formulated to set within seconds to minutes of application.
Proper surface preparation is vital to the performance of a polyurea coating system. In most cases, abrasive sandblasting or primer applications may be necessary to remove any foreign contaminants and ensure adequate adhesion.
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