Epoxies:

Epoxies were commercialized in the 1950s and are resin-based polymers utilized for their unmatched adhesion strength and durability. These attributes are achieved via epoxy's inherent chemistry, which makes it cure slower and penetrate further into concrete substrates, creating a superior bond for the coating system as a whole.

Epoxy can be applied at a much thicker mil rate than other polymers (from 15 to 50 mils). The added thickness improves the appearance and structural integrity of older concrete floors, which can often be wavy and in disrepair, and also provides increased durability, strength, and impact resistance. Epoxy also has a significantly greater tolerance for being applied to concrete that has higher moisture levels.

Industrial-strength epoxy (not the product sold in kits at retail stores) is the industry standardand is used by the majority of industrial and commercial coatings companies. These companies install polymer concrete coatings in the most demanding locations, including large factories, distribution centers, warehouses, and airplane hangars. They have become so well known, that many use the term "epoxy" as a universal term for any type of polymer coating.

Advantages of Epoxy Coatings:

• Slow curing time / longer Pot Life (allows for deeper penetration into substrate)
• Exceptional substrate adhesion (ASTM-7234 Pull Off Adhesion Strength)
• Exceptionally strong impact resistance - 10,000+ PSI pushing on surface (Compressive Strength)
• Higher tolerance to permanently bond to wet concrete with high MVER (Moisture Vapor Emissions) from 3 lbs. to 20 lbs.

Disadvantages of Epoxy Coatings:

• Require extensive surface abrasion (CSP2 or CSP3) to allow for 3-6 mils of penetration into substrate
• Longer back-to-service time
• Less chemical resistance than other polymers
• Lower uV Resistance - May amber, fade, or yellow over time

Polyureas:

Polyureas are considered the new kids on the block when it comes to polymer coatings. However, they have been around for more than 20 years. Because of their chemical resistance, polyureas were initially developed for corrosion protection in metal pipelines, water towers, and liquid storage tanks. Historically, they have been applied through specialized spray guns, due to their thinner viscosity and extremely fast (almost immediate) curing times. This makes polyureas ideal for coating vertical and rounded surfaces.

Over the years, large chemical companies have reformulated polyureas to allow for easier use by extending their working times, which has enabled them to be used in other industries, such as concrete flooring. Eventually, using a molecular alteration, manufacturers recently created a different type of polyurea known as polyaspartic.

Both products, regardless of the nomenclature, have nearly identical attributes, including fast curing and exceptional elongation rates. Polyaspartics generally contain higher solid content than polyureas and, as previously mentioned, are widely accepted as the premier, protective top coat in many industrial coating systems (because of their increased chemical-resistance, abrasion resistance and uV stability).

Additionally, polyureas have an extremely low tolerance for any moisture (as you might recall their roots were designed for applying to metal - not concrete). This can make polyureas more vulnerable to delamination or adhesion failures when applied to concrete, when compared to industrial-strength epoxy.

Advantages of Polyurea (Polyaspartic) Coatings:

• Chemical resistance superior to other polymers
• uV Stable - less likely to amber, stain, or discolor
• Shorter back-to-service time
• Excellent abrasion resistance and flexibility

Disadvantages of Polyurea (Polyaspartic) Coatings:

• Fast curing time (allows for minimal penetration into the substrate)
• Vulnerable to delamination & low tolerance for any substrate moisture if utilizing as base coat
• Must be applied thin, not allowing for maximum system build when broadcasting a flake into it
• Generally higher VOCs and odor due to containing more solvents than industrial-strength epoxies

One-Day vs. Two-Day System Claims:

Anyone considering a full broadcast system for their garage floor will likely encounter many claims regarding all the aforementioned products. Below, we summarize and clarify many of those claims to assist you in making an educated decision, based on factual and accurate information.

Industrial epoxy is indeed an older coatings technology, making it tried and true. Though they may appear to be casual environments, residential garages are some of the most abusive environments around and require coatings that can withstand the weight of vehicles and resist delamination from contact with hot tires, which can reach temperatures as low as 30 degrees in the winter and over 150 degrees in the summer.

Industrial-strength epoxy, while older than some of the other polymers, remains the preferred product to connect a coating system directly to concrete. Industrial epoxy's ability to cure slowly and wick into the prepared concrete surface allows it to integrate into the concrete (3-6 mils) and create a tenacious and permanent bond.

Quicker-curing polyurea base coats are renowned for not bonding as well to bare concrete and also lacking moisture tolerance, both of which could make them susceptible to delamination over time. Regardless of the recent technology improvements made with polyureas, the time-tested effectiveness of utilizing high-solids, industrial epoxies as the base coat are proven and trusted by the coatings industry. This is why industrial epoxies continue to be the product of choice by coating manufacturers, industrial-coating supply houses, and commercial coating contractors alike.

The bottom line is that there is no one-size-fits-all approach to coatings. So, when selecting the correct coating system for a specific application, the decision should be driven by which products will deliver the highest-quality system to the consumer and not what is easiest or fastest for the installation company.

There are undisputed attributes of polyaspartics and polyureas that are superior to industrial epoxies, as discussed above. Some of these attributes include abrasion resistance, chemical resistance, uV resistance, and back-to-service times.

However, none of these polyurea benefits pertain to what remains the lowest-common-denominator in coating systems: The durability and longevity achieved through permanent adhesion to the concrete. Without a permanent bond, all of the other ancillary benefits of the garage floor coating system are negated.

Polyureas were not originally engineered for bonding strength to concrete. They were developed to be applied at a thin mil to achieve a quick bond to non-porous metals, with a focus on their superior chemical resistance and uV stability. More recently, One-Day installers have touted polyurea's greater elasticity. While this may be true when laboratory tested independent of other products, most manufacturers agree that a polyurea having greater flexibility is more of marketing point and not an important product characteristic when coating concrete in a residential garage.

In contrast, industrial epoxies have been proven for decades to be the best polymer for bonding directly to concrete and remains as the best option for experienced, commercial coatings installation companies to use as the base coat in garage-floor coating systems.

The reality is that systems using a polyurea base coat are easier and less time-consuming to install, as they only require one day for installation. One-Day garage floor companies often state that they provide warranties ranging from 15 years up to limited lifetime warranties. How are such warranty and longevity claims substantiated, when the products used for One-Day garage floor coating systems are new to the market and untested for such extensive longevity claims.

Countless companies that install One-Day garage floor systems publish claims that their systems using polyurea base coats are up to 20 times stronger than systems using epoxy base coats, while presenting no factual data to support their statements. These claims are misleading, as there are many variables in play when comparing the strength of any polymer's bond to concrete.

The Bonding Strength, which is the measurement of how well a polymer bonds to the substrate, is considered the most important "strength" attribute. No other strength-related traits have any merit if the coating's bond to the substrate is not permanent. For example, if the bond strength of the polymer is greater than the tensile strength of concrete itself, then the strength limitations will cause the concrete to fail prior to any polymer failing, be it polyurea or epoxy. This is measured by the ASTM D-7234 test, which is the Standard Test Method for Pull-Off Adhesion Strength of Coatings using an Elcometer as demonstrated below.

Many of the One-Day garage floor companies state that their total system build is equal to that of the Two-Day garage floor systems, and others conveniently omit this system characteristic. The thickness of a garage floor coating system is extremely important. If a coating is too thin, it will not provide sufficient protection during the day-to-day rigors of garage use. In contrast, if a coating is too thick, it will become too brittle. So, utilizing the correct product at the correct thickness in each stage of the process is vitally important for durability and longevity.

Polyureas can be prone to outgassing if applied too thick and are normally installed at 250-375 square feet per gallon (4-6 mils per coat). This creates an extremely thin base coat, in comparison to industrial epoxy base coats that are typically applied at 100-160 square feet per gallon (10-16 mils). Potential issues of a base coat being too thin are:

• Inconsistent coverage: Without enough base coat material to receive the broadcast medium (flakes), the base coat may be visible following the application.
• Reduced impact resistance: If less broadcast medium adheres to the base coat, it results in less of the protective top-coat material being applied to encapsulate the flakes.
• Less long-term durability: Using thinner polyurea base coats can lead to the overall system thickness being up to 50% less than a hybrid system utilizing an industrial epoxy base coat.

One-Day systems that use a polyurea base coat may allow for a full return to service within 24 hours, due to their faster curing times and thinner application. Two-Day systems using a hybrid approach allow for a next-day return to limited service (foot traffic & personal items), with vehicles allowed a few days later.

For this reason, One-Day systems can be the right option in settings that require as little downtime as possible (retail/commercial businesses) and that have little or no vehicular traffic. So, if being displaced from your residential garage for only one day is a higher priority than the longevity and durability offered by a hybrid, Two-Day coating system (using an industrial epoxy base coat and polyaspartic top coat), then a One-Day installation might be a good fit for your needs. This begs the question: if One-Day systems were actually better overall concrete coatings products, why would most industrial coatings contractors not use them as their standard base coat application?