Maximizing dirt-pickup resistance (DPUR) is a key requirement for many exterior coatings. For example, in roof coatings, in addition to aesthetic considerations, maintaining a dirt-free coating can result in significant savings on energy costs, since a white coating will not absorb as much solar energy versus a coating that is soiled.
While it is generally known that higher glass transition temperature (Tg) resins impart improved DPUR due to a harder film that is formed, stricter VOC regulations have resulted in the use of lower Tg resins in traditional exterior architectural coatings. This has limited the extent to which high-Tg resins can be used, as formulators generally desire a single national formula that conforms to the widest range of regulations from various jurisdictions.