Issue 10: Understanding Polyurea Hybrid Coatings; What is the mix

Issue 10: Polyurea Hybrid Coatings: Understand the Differences

Sometimes a customer is told that a supplier has a polyurea hybrid and that a hybrid will outperform polyurethane because of the polyurea component of the formula. However, all polyurea hybrid coatings are not created equal.

UV Stable Polyurea School Staircase; Get the Correct Coatings

Most customers take what they are told at face value, without a more in-depth understanding of the issues involved. Customers should ask questions. If the polyurea component is the determining factor that boosts the physical properties, exactly how much of the hybrid product is polyurea coating and how much is polyurethane? One supplier could offer an 80% polyurea coating/20% polyurethane mix to get one level of performance; a second could have a 50%/50% ratio to have a perfectly balanced blend, according to its claims; and a third could use a 99% polyurethane/1% polyurea coating system. While each supplier would be correct in calling their product a Polyurea Hybrid, the customers of each would be purchasing a coating with drastically different performance characteristics.

It’s extremely important to know what you’re buying. Too many coating specifiers are unaware of the subtle differences in these coatings and their properties. Every contractor should either seek out specifiers that understand the key differences between polyurea hybrid coatings or be willing to train the specifiers with whom they work.

Issue: 9 Safer is Always Better

Safer is Always Better

Many safety issues surround polyurea coating handling and application. Appropriate personal protective equipment (PPE) should always be used according to the polyurea coating system and the application equipment used. The safety of applicators, observers, and unknowing passersby is critical, as underscored by OSHA regulations.

The use of PPE cannot, and should not, be the only way to stay safe. The real risk to the polyurea coating spray applicator stems from the actual chemistry itself. These materials are reactive. Even though they can be touted as environmentally friendly once cured, they must be respected and handled with caution during application. Safer formulations should be available to applicators choosing to limit risk exposure while handling and applying the coating.

Methylene Diphenyl Diisocyanate (MDI) adds another facet to the safety issue.  While MDI has a variety of forms, it’s well known that exposure to vapor or small particle MDI can cause sensitization, health-related problems, and death. To date, there have been at least four deaths attributable to MDI overexposure. The federal government issued a report after the causes of the deaths had been investigated. Tragically, the investigation was limited to exploring the circumstances surrounding these deaths and the PPE that should be used in their light, not what can be done to mitigate and reduce these risks from an equipment or application method viewpoint.

Alternative application methods and/or techniques, along with different equipment options, could greatly reduce risks arising from spraying polyurea-type coatings. However, large equipment manufacturers have no incentive to bring attention to such possibilities, since employing safer spraying parameters would include not purchasing or using the equipment they presently offer.

Common sense safety precautions include covering the skin, wearing eye protection, and using a National Institute for Occupational Safety and Health (NIOSH)-approved respirator. When spraying isocyanate-based (MDI or other) material, wear a respirator at all times; and, if spraying in a confined space, a supplied air respirator.

But don’t only consider respiratory protection in assessing the equipment necessary to manage the health risks posed by spraying polyurea types of coating systems. The increased risk of skin contact from spray mist when spraying polyureas, polyurethanes, and polyurea hybrid materials using high pressure spray equipment is also a considerable concern.

Anyone having experienced high pressure spraying, hot spray, is familiar with the mist cloud that forms around the spray area and moves with any air movement. This mist contains reacted, reacting, and unreacted particles of isocyanates, amines, polyols, or other additives included in the original formulation. Therefore, it’s recommended that not only the skin surfaces of the body be fully covered, but also that a full-face respirator be used to protect the eyes and facial skin from the coating mist moving around the sides of protective eye wear or face shields and being deposited onto the skin. A hooded suit, or head sock, may also be worn to protect the heads of those within the spray area.

The link between particle size and potential health risks is not generally discussed in trade publications.  In fact, there is a direct relationship between smaller particle size and a higher likelihood that the particle could pass through, or around, safety equipment and/or be deposited on something that is touched later when the user is not wearing gloves. Exposure to the chemicals can result before, during, or after actual spraying. It’s imperative to consider personal protection during the entire process: arrival, taping or masking out, equipment setup, substrate preparation, test spraying, actual job spraying, unmasking or untaping, clean up, and use.

Since smaller particle sizes are suspended in the air more easily, and are more easily passed through or around safety equipment, larger particle size application equipment should be considered a safer alternative—that is, cold spray and warm spray low-pressure equipment.

Issue 8: UV stable coatings or “what are Aromatic vs. Aliphatic coatings?”

The Importance of Aliphatic Coatings and UV-Stability

In theory, UV-stable products should have very little loss of gloss or color fade over time, even when exposed to sunlight. On the other hand, non-UV-stable products will first lose gloss when exposed to sunlight, then fade and/or yellow, and, eventually, experience polymer breakdown and coating failure. By definition, aliphatic polyurea coating systems are UV-stable, while aromatic polyurea coating systems are not. What seems pure and simple, is neither pure or simple.

Labels of aliphatic coating products can be deceptive. Although a number of aliphatic systems are truly 100% aliphatic, there are too many aliphatic products out there that are, in fact, blends of aliphatic and aromatic. Some producers will make a blend that is only 51% aliphatic and 49% aromatic and still claim it is an aliphatic product. While there is some argument for this being true, is the customer educated during the purchasing process?

Educate yourself. When purchasing an aliphatic system, ask the producer about the percent of aliphatic materials in their product. Read the product’s Material Safety Data Sheet (MSDS). An aliphatic polyurea coating will contain only IPDI and/or HDI isocyanate (Side A) component. An aromatic polyurea coating uses MDI or TDI isocyanate. Since MDI and TDI are not UV-stable, you should not find either of these components in a truly aliphatic product.

Aromatic Vs Aliphatic Coatings in UV Testing


Issue 7: One Size Fits all Fallacy

The One-Size-Fits-Fallacy

Polyurea coatings and polyurea hybrid coatings are generally both high performing and weather tolerant in ambient application conditions of both high and low temperature. Polyurea coating tends to be highly flexible and waterproof–a good, tough, all-around coating. However, substrate (surface) and application conditions, product usage, application options, chemical and atmospheric exposure considerations, and other factors must be considered when selecting both a coating system supplier and a coating system.

Industrial Coatings requirements are different from Residential and Commercial floor coatings

Many suppliers or marketers of polyurea-based systems take a “one-size-fits-all” approach. They offer a strong, waterproof, durable, product you can use for your roof, your fish ponds, your truck bed liner, your deck, your garage floor, or wherever you have a need. While you could use it that way, don’t assume that a specific polyurea coating system is either the best, or even the safest, product for every application.

Exterior Weather and Wear is different from an interior Store Floor

It’s vital to determine the different exposures (how it will be attacked) and service conditions that the coating will experience before selecting a coating system for a job. Depending on its application, some polyurea coating formulas may work well, whereas others may be inappropriate. For example, a fish pond polyurea hybrid coating can be waterproof, durable, tough, and seamless; but, if the formulator does not use a catalyst that either becomes part of the polymer matrix or is benign to fish, the catalyst will leach out of the coating system and kill the fish!
Unfortunately, the polyurea coating market is being overtaken by short-sighted salesmen wanting to make money quickly. The industry is, in large part, lacking the customer service specialists whose primary interests are to match the end-customers’ needs with the best solutions. Look for coating systems specialists that understand that only by solving each customer’s specific need will they create a customer for life.

Food Processing Work Area Coating

Issue 6: 100% Resin Vs Fillers

Resin Versus Fillers

3d Molecular structure  illustration










Many producers of protective coatings claim that the product they are trying to sell a customer is 100% Solids, suggesting that it contains no solvents. However, they may not be forthright about the amount of non-resin components that have been added to it to reduce cost and increase profit. These additives decrease performance, because resins build a coating’s physical properties, while fillers typically only build volume.

In conversations with sales or technical representatives of companies marketing protective coatings, ask them about the use of resin components versus fillers in product formulations.

WB SEALER SYSTEMS, LLC  uses only materials with no fillers

Contact us at 603-353-0432;


Issue 4: Significance of Cross-link Density

The Significance of Cross-Link Density    

Cross-link density refers to the way polymer threads are woven together and the density or packing of those threads. The higher the cross-link density, the better the barrier-type properties of a coating system.

An example illustrating the cross-link densities of two different polyurea coating system formulas is chain link fence vs. chain mail armor. Both are made of metal, are woven together, and offer a certain level of protection. If a circus performer were to throw an ax at you, you could feel equally confident of your safety by standing behind either a section of chain link fence or a section of chain mail armor. In both cases, the molecule size of the ax cannot penetrate the cross-link density of your formula. However, if that same circus performer were to throw a razor-sharp 7” balanced knife at you, you would probably not feel the same level of confidence standing behind the fence as you would the armor. Why? Because the cross-link density of the armor doesn’t allow the small molecule knife to pass through. Which would you choose for protection, the chain mail or the chain link fence?

In comparing Polyurea coating systems, cross-link densities are not all the same. Although similar, the end results, and the level of protection offered, can be very different from one formula to another. By design, coatings with no solvents or volatile organic compounds (VOCs) of any kind (listed, exempt, or other) have the capacity of exhibiting the highest cross-link density.

Don’t be deceived or misled. The use of any solvent in a coating system is both a performance and safety concern. Look for materials which are designed for the specific needs of your project

Issue 1 Open Time

Open Time

Open time (or working time) in the chemistry of two-component coatings is the elapsed time between when the two coating components are mixed together and when they have sufficiently reacted that they are no longer workable.  Gel time in high performance coatings is the elapsed time from when a coating is placed onto a surface until that coating can no longer be moved around.

Typically, pure polyurea coatings react very quickly.  Historically, they’ve been applied using high heat and high pressure spray equipment, with gel times typically in the three- to seven-second range.  The application equipment has a spray gun, the direct impingement gun, bringing the two components of the coating system together under very high pressure, forcing them to react with each other.  Frequently referred to as hot spray, it’s widely used in polyurethane spray foams and two-component coating systems like polyurea and polyurethane coatings.

However, the latest formulation techniques available today allow specific raw materials to be blended together, providing a much greater open time.  The longer open time enables the polyurea or polyurethane coating, or polyurethane spray foam, to be sprayed through a relatively inexpensive gun that contains a static mixer spray nozzle rather than a high-cost impingement spray gun.  This equipment is frequently referred to as cold spray.

The crucial point about open time is that the faster the coating gels, or sets up, the less able it is to flow into, and conform to, the landscape of the surface being coated (known as surface profile or anchor profile).

In discussions of coatings, you may hear references to the wet out properties of a coating product.  The property of wet out, or wetting out, of a coating is its ability to conform to all the surface profile—that is, fill in all the little valleys and crevices so that a good mechanical bond is obtained.  The graphic below demonstrates this point.

Everyone wants a fast cure product; but, if it cures too fast to conform to the surface profile, the risk is catastrophic adhesion failure.

WB Sealer Systems, LLC uses formations which have open times up to 20 minutes for successful application and installation. This provides efficient installation with superior properties in the finished coating.