High-performance coatings are formulated to react predictably if application temperature expectations are met. Made by a combination of reactive components, these products are formulated to use the surrounding air so that a liquid converts to a solid in a relatively short period of time. Why does this matter to an installer?
A high-performance coating, once mixed, has a fixed amount of time to be placed, react, and harden, otherwise known as form, cross-link, and cure. It’s during this chain of events that product, slab, and air temperatures are assumed to be within the range specified by the product manufacturer. If the temperature is outside the product’s specified range, then the placement, reaction, and final strength will be affected. The purpose of this article is to impress upon the reader the importance of understanding site temperature conditions and how they can affect common coating types, particularly epoxies.
Temperature-influenced placement issues arise when the product, slab, or air is outside the product’s specified range. Epoxies, polyaspartics, and urethanes are fluid-applied products. Similar to maple syrup, these resins will be thinner (aka lower viscosity) as they are warmed and thicker (aka higher viscosity) when they are cooled.
To help the installer, information about recommended temperatures for a specific product can be found in any technical data sheet (TDS). The TDS will state the temperature at which the product has been tested for its formulated viscosity. Some documents may actually provide a product’s centipoise (cP) to quantify the liquid resin’s fluidity. To keep it simple for the product user, the manufacturer provides an easy-to-verify site condition that is important and should be considered.
Resin flow rates aside, the temperature’s role in how a resin will react is equally as important. The reaction that converts a fluid to a solid requires heat and/or moisture to get the job done. Product, surface, and air temperatures are all going to affect the reaction’s efficient use of the required heat or moisture. In short, the faster a resin heats or cools in an environment will affect its final performance. Hardness, chemical resistance, and even attachment to the slab can be negatively impacted by temperatures outside the manufacturer’s specified range. This important information, again, will be stated in a product’s TDS.
Chemistry of Epoxy
Most epoxies are created by combining an epoxy resin (Part A) and a hardener (Part B). These components react with one another in a process known as cross-linking. This is best explained as a mixture of compounds that attach to one another to form a dense matrix. The more complete the cross-linking process, the closer the compounds are locked together. It’s important to note that this reaction is exothermic, meaning heat is created by this process, and ambient temperature at the time of the reaction influences how complete the reaction will be. If the epoxy’s reactive elements are above or below the manufacturer’s stated temperature range, then the creation, management, and consumption of heat will be altered — resulting in an epoxy that doesn’t cure properly.
Two common epoxy terms that most installers will eventually hear are:
1. amine blush (too cold), and
2. flashing (too hot).
An amine blush is the result of Part B hardener not reacting fully with the Part A. This can also happen when formulas are thinned by solvent, measured incorrectly, or incompletely mixed. For the purpose of this discussion, it’s assumed the product has been mixed according to the manufacturer’s instructions (TDS). Why, then, is a cool environment likely to cause an amine blush? Remember that these products require heat (generated by the chemical reaction) that can be used before the environment absorbs it. If the product, slab, or air temperatures are low, some heat will be stolen before it can complete the reaction. While an amine blush is disappointing to see, there are several fixes that may help to avoid removing the coating completely. However, prevention of an amine blush should be the goal of any pour.
Similar to epoxies, polyaspartic coatings utilize a two component formula: Parts A and B are mixed according to the product’s TDS, and the chemical reaction begins. Unlike epoxies, though, polyaspartics rely upon moisture, in the way of humidity, to react. This means the environment is very important to completing the reaction. While a lower temperature may slow this resin’s time to cure, unlike an epoxy, it will still complete the reaction.
As for limitations caused by the environment, a polyaspartic’s designed use of air to cure means high temperatures and/or humidity can cause the product to trap bubbles. The polyaspartic formula creates CO2 during the reaction process, which is called off-gassing. This CO2 must be expelled before the resin’s rising viscosity traps the gas. If the gas is not released, then bubbles are likely to form in the hardened coating. This may show up in a clear polyaspartic with a white cast, or excessive contouring.
While coating thickness can play a part in this problem, temperature and humidity have more influence than any other factor. The best way to prevent polyaspartic failures is to fully follow the product’s TDS with respect to application temperatures. One additional note to prevent excess temperature and humidity from fouling a batch: The mixing procedure stated in the TDS should be followed. Air is brought in to the resin as the two components are mixed. Excess air introduced by aggressive mixing will speed the polyaspartic’s reaction time, too.
Urethane coatings are traditionally used as topcoats, because they exhibit excellent chemical and abrasion resistance. Though also used as an industrial body coat by way of urethane cement, urethane coatings in this discussion pertains to their use as a coating system’s traffic layer.
Sometimes made of two components and other times of a single component, urethane coatings cure the same way as polyaspartics. The challenge with urethane topcoats, as relates to temperature, is the importance of the material’s viscosity to installation ease. The urethane acts as a traffic and chemical-resistant coating, but the final installed thickness is usually 5 mils (127.0 microns) or fewer. If the air temperature is outside the specified installation temperature per the TDS, the installer may have trouble applying the product without leaving behind roller marks or having the ability to control the application thickness. In addition to temperature causing installation difficulty, product cure rates will be affected. In the case of the temperatures being lower than specified, the product will require more time to be traffic ready and chemically resistant.
While this article has only focused on one aspect of coatings’ chemical technology — temperature — hopefully it serves as a reminder to verify all specified limitations. The coating technologies that exists today are more advanced than they have ever been. Unfortunately, even manufacturers have yet to engineer products that can ignore mother nature’s influence.
About the Author
Josh Jones has been working in the industries of surface preparation and polishing for 29 years. He works for Substrate Technology Inc. (STI) as their technical trainer and company president. Besides being active helping STI customers, he also utilizes social media to provide video demonstrations of surface preparation best practices. For more information, contact: Josh Jones, firstname.lastname@example.org, https://substratetechnology.com