Development of Low-VOC 2K Waterborne Polyurethane Anti-Graffiti Coatings

By Xiaodong Wu , Richard P. Rosen

Whether it is viewed as art or awful, graffiti has been targeted by the growing arsenal of technology. It is estimated that the cost of graffiti abate­ment programs runs in excess of $12 billion annually in the U.S. alone. It has been reported that fluorinated polymers are the best candidates to give a coating surface with low surface free energy, to render hydrophobic and oleophobic characteristics. In addition, fluorinated polymers excel in dura­bility and weatherability in comparison with other materials.

The development of coatings having anti-graffiti performance has been ongoing for many years in the coatings industry. Coatings based on urethane chemistry remain the preferred technology for permanent anti-graffiti coat­ings due to the overall film properties, including mechanical properties, durability, and light stability. The most common approach is to make a coat­ing with a very low surface free energy by incorporating fluoro-, perfluoro, or silicone component in the formulation.

However, the resulting non-stick surface would lead to the problem of recoatability. After its service life, the coating has to be stripped before a new coating is applied.