By Mike Diebold and Grant C. Bleier, The Chemours Company
Maximizing a coating’s durability is a complex equation that must account for multiple factors.1 Making matters even more challenging is the fact that formulators have been missing a critical piece of information about how titanium dioxide (TiO2) can influence durability—until now.
Today’s paint producers and formulators are under heightened pressure to create highly durable coatings for exterior architectural and industrial applications capable of standing up against harsh UV rays, rising temperatures, and severe weather events. At the same time, many applications also demand greater efficiency via longer-lasting coatings that increase the length of service before recoating and reduce material and labor costs.
TiO2, a critical component of high-quality, highly protective coatings, is known to have several effects on paint durability that formulators must consider.2-10 As a strong UV light absorber, TiO2 protects underlying resin from direct interactions with the UV component of sunlight. However, TiO2 can convert some of the UV light energy into chemical energy in the form of radicals, which can then attack the binder or react with other molecules at the surface that can lead to further paint degradation. In addition to the inherent photoactivity of the TiO2 pigment, the degree of TiO2 dispersion also plays an important role in determining a paint’s durability.
It is logical for formulators to assume that by decreasing the photoactivity they can create a more durable coating. However, a more nuanced approach shows that TiO2 grade can affect paint durability beyond simple TiO2 photoactivity.
Closing a Crucial Information Gap
It has been previously established that initial paint gloss—a paint characteristic that is highly representative of pigment dispersion—has an effect on gloss retention independent of TiO2 photocatalytic activity.11 However, the effect of degree of dispersion on color stability (fade) of paints has not been studied in the same way. This is because the durability of paints with poor TiO2 dispersion is seldom measured. Durability testing is expensive and time-consuming, whereas TiO2 opacity testing—which is also related to degree of dispersion—can be used to identify and reject poorly dispersed paints quickly and for little cost.
As such, there is limited information available that separates the effect of TiO2 dispersion on paint durability from the effect of TiO2 photocatalytic activity. This information gap has made creating coatings that maximize paint durability challenging for formulators.
To create high-quality paints that provide a high level of protection from the elements, formulators must fully understand the relative importance of photoactivity and TiO2 dispersion on paint durability. At Chemours, we wanted to measure and quantify this relationship to help formulators make the highest-quality products possible. To do so, we conducted an experiment to shine a light on this process and uncover exactly how the degree of TiO2 dispersion can affect color stability, a critical aspect of a coating’s durability.
Continue reading in the July-August digital issue of CoatingsTech.