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The Differences between Epoxies, Polyurea and Polyaspartic Coatings

Owners have several options to choose from when selecting the appropriate resinous flooring system for their project. Whether it be for a commercial application or a residential garage floor, the materials used will have a significant impact on the long-term performance.

These days there is quite a bit of information out there regarding various coating options and how they compare to one another. As a material manufacturer, Resinwerks produces a variety of products for different applications, and it is important that owners and specifiers have a comprehensive understanding of each. Some of these materials are used as primers and base coats for various reasons while others are best suited as topcoats.

Points to consider when comparing different coating materials:

  1. Chemistry
  2. Long Term Performance
  3. Cost

Chemical Makeup:

Epoxies:

Epoxy floor coatings are created by reacting an epoxy resin with a hardener. Epoxies encompass a large group of polymer formulations that are spread across many groups. Engineered for use in a variety of applications, epoxies contain numerous purity grades, viscosities and performance attributes that can be tailored to specific applications. Epoxy resins are quite stable at room temperature and gain their ultimate performance characteristics only when reacting with curing agents like polyamines, aminoamides and phenolic compounds. They can be used in applications requiring high chemical resistance and offer superior adhesion to a variety of substrates including concrete. In general, properly formulated 100% solids and water-based epoxies will provide for superior long-term adhesion to concrete.

Polyureas:

Polyureas were originally developed as water-resistant coating for steel and have been widely adopted due to their fast gel times and elastomeric properties. They have been used for years on applications such as truck-bed linings, pipe coatings and tank linings. While polyurea was never developed or intended to be used as a concrete coating, it is used today as a direct to concrete primer – often as a base-coat for flake broadcast systems. Conventional polyurea polymers are created using aromatic methylene diisocyanate (MDI) and amines. Aromatic based two-component polyurea systems have been the workhorse of the two component polyurea technology. Aromatic compounds like conventional polyureas are susceptible to UV degradation for a host of reasons and will yellow/degrade under UV exposure.

Urethane Cement:

Also commonly referred to as Urethane Mortar or Polyurethane Concrete, Urethane Cement is created by combining a high-performance polyol emulsion and MDI with cement compounds & aggregate. This matrix generates a mortar that when cured is highly resistant to thermal shock and impact. It is also highly chemical resistant, making Urethane Cement an ideal choice for food & beverage applications. Urethane cement provides for high moisture vapor tolerance and is also suitable for slabs with higher soluble salt contents. Like Polyureas however, they are aromatic and will discolor over time.

Polyaspartic Coatings:

Technically referred to as Polyaspartic Aliphatic Polyurea, polyaspartic coatings were first introduced in the early 1990s. Polyaspartics are based on the reaction of an aliphatic polyisocyanate and a polyaspartic ester, which is an aliphatic diamine. Some industry representatives will advance that polyaspartics are a form of polyurea. This is only partly accurate. In addition to using more refined resin components, Polyaspartic coatings are catalyzed by way of an aliphatic (UV stable) Hexamethylene Di-Isocyanate hardener. In addition to non-yellowing attributes, Polyaspartics exhibit a host of other superior performance capabilities. They provide for very good flexibility and superior concrete wetting abilities, making them excellent primers for direct to concrete applications. Polyaspartics also provide for superior abrasion & chemical resistance, which helps to prevent against degradation from caustic soluble solutions that may present over time within existing concrete slabs.

Key Factors Impacting Long-Term Performance:

Adhesion:

When properly formulated and applied to properly prepared substrates, most materials will provide for adequate adhesion to concrete at the time of installation. Adhesion is measured by use of a pull test as per ASTM D4541. In using this method, pull tests will fracture the concrete at or above 400-500 PSI. In some cases, epoxies (especially water-based and vapor-barrier epoxies) or polyaspartics will provide for superior concrete wetting abilities, providing for greater bond strength in commercial & Industrial settings with higher PSI concrete. Urethane cement systems are applied over heavily profiled floors designed to provide an anchor for the thicker mortar.

Impact Resistance

In addition to pull tests, owners may consider how impact resistance will influence the longevity of their floor. Generally speaking, polyaspartics and polyureas will provide for an element of flexibility that may enhance impact resistance. Many epoxy primers however are also formulated with additives to augment flexibility and increase impact resistance. In fact, flexibe epoxy membranes are widely used in commercial & industrial settings as crack suppression membrane underlayments as well as elastic joint fillers for a host of commercial flooring applications. For applications in residential settings, epoxies provide for optimal adhesion and are more than adequate from an impact resistance perspective.

Moisture & Chemical Resistance:

The leading cause of resinous flooring failures for properly prepared concrete substrates is elevated moisture vapor emission rates. All slabs contain soluble salts as well as some level of moisture. When moisture levels are elevated, water mixes with the soluble salts within the slab to produce a corrosive solution that attacks the bond point of coatings, adhesives, etc. Along with a high PH,

Certain types of Epoxies, usually referred to as Vapor Barrier or Moisture Mitigation Epoxies are engineered to be highly chemical resistant and will hold up against this corrosive solution. These types of epoxies are effective in areas experiencing high levels of humidity/moisture as well as older concrete slabs that may not have a plastic membrane under the concrete slab.

Lacking adequate chemical resistance, polyurea coatings and standard epoxies will not have the same level of long-term protection against moisture in concrete slabs as Vapor Barrier Epoxies. Polyaspartic coatings will provide for an added level of chemical resistance, however they are not specifically formulated for concrete slabs with high moisture vapor transmission rates. Urethane cement systems generally have very good resistance to moisture vapor emissions.

UV Stability:

Polyaspartic coatings are “aliphatic” UV stable materials. They will not degrade or yellow if exposed to sunlight or UV rays. Polyureas and Urethane Cement materials use “aromatic” hardener formulations. These materials will tend to discolor when exposed to UV. This is one of the reasons why polyureas are pigmented and not used as top coats. Epoxies have varying degrees of UV stability. Some epoxies exhibit very good weathering abilities and are resistant to ambering over the long term. These materials utilize a refined resin matrix that is catalyzed with a water-clear cycloaliphatic hardener.

Product Cost:

Epoxy coatings cover a wide spectrum in both quality and formulation. Costs of epoxies will also range significantly. Cheap epoxies such as those available at the big box stores are not the same as high-performance coatings or epoxies built to tolerate high vapor emission slabs.

One of the significant benefits to Polyurea coatings is that they are very inexpensive to make. They provide installers and owners with a cheaper option when compared to polyaspartics and most epoxies. The cheap cost of Polyureas has led many manufacturers and franchise networks to aggressively promote polyureas.

Polyaspartic coatings incorporate highly refined resins and hardeners. As such, performance characteristics and associated costs of polyaspartics are generally higher when compared to polyureas and generic epoxies. Urethane Cement systems will also tend to be more expensive from a material cost per square foot standpoint.  

Summary:

As a manufacturer, Resinwerks has extensive experience in developing and manufacturing several types of high-performance resinous flooring products. Selecting the right material for your project largely depends on balancing the benefits between performance and cost. There is no single product that is best for all projects, and it is important to rely on your installer and manufacturer for expertise on what system is best suited for your application.

Remain cautious when hearing claims such as “our product is 5x stronger than epoxy”. The scope of resinous flooring products available today is far too complex for these types of generalities. DIY epoxy available for purchase at a big-box store is going to be far less capable than an epoxy supplied by a high-performance coatings manufacturer. Many epoxies will in fact offer superior chemical resistance and adhesion when compared to polyureas.

Moisture is a measure in time and place. Moisture Vapor Emissions in a concrete slab may look completely different after a seasonally wet period (as most of the US has seen in 2022-2023). Polyureas provide for a low-cost option, however they may not provide the same level of long-term performance as other types of materials – especially when it comes to adhesion.

Polyaspartic chemistry incorporates advanced formulas and curing agents that provide for superior chemical resistance, UV stability and impact resistance. Polyaspartic make both excellent topcoats as well as primer and intermediate coats. Epoxies are excellent primers and certain Vapor Barrier Epoxies are engineered to help to protect against long-term moisture failures in concrete.

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