Breakthrough Waterborne Technology Brings Alkyd Back to the Road

By Jamie Dziczkowski

According to National Association of Clean Air Agencies (NACAA), pavement-marking or traffic paint is defined as a coating labeled and formulated for marking and striping streets, highways, or other traffic surfaces including, but not limited to, curbs, crosswalks, driveways, parking lots, side-walks, and airport runways. These coatings are an essential safety feature of modern infrastructure. They provide visibility to pedestrians and drivers through specific colors and incorporation of retroreflective elements, such as glass beads. Key performance attributes are the ability to adhere to and retain the retroreflective elements to maintain good nighttime visibility, adhesion to the surface for sustained durability, and ease of application. Generally, this market is driven by low cost coupled with high performance, although there are a wide variety of pavement-marking systems available depending on budgetary needs and performance requirements.

Historically, solvent-based products, mainly alkyd paints, were heavily used in this industry due to their low cost and wide range of application conditions, especially their reasonable dry times in colder temperatures and high humidity. This is mainly attributed to the hydrophobic nature of solvent-based paints, in which the drying mechanism is mostly independent of water vapor in the air. However, as a result of stricter environmental regulations, technology changes have altered the distribution of traffic paint, favoring waterborne systems. Starting in the late 1980s, waterborne traffic paint use began to climb and now has the majority of the volume in this market.

The latest acrylic waterborne technology utilizes a pH-triggered mechanism that provides a quick set of the binder through adjustment to high pH with a volatile base, such as ammonium hydroxide. The high volatility of the ammonia lowers the pH of the film quickly and allows the film to rapidly build and hold integrity. However, the paint is very odorous, and stability issues can arise if the pH of the paint falls below a certain level before application to the surface. There are other niche coatings used on the roadways which consist of high performance epoxy, modified epoxy, MMA (methyl methacrylate), and polyureas, but they are used at much lower volumes. Figure 1 shows the market allocation shift, by volume, of the traffic paint industry in 1985 versus 2011.