A new hardener from Bayer MaterialScience makes possible graffiti-resistant waterborne coatings

Wiping out graffiti

Every year Germany spends up to 500 million euros to remove graffiti. In the future, these costs can be reduced by using waterborne two-component polyurethane paints formulated with raw materials developed by Bayer MaterialScience. The new product must first “show its true colors” in laboratory tests. For this purpose, a commercial spray paint is applied to a panel that has previously been treated with the anti-graffiti coating.

Graffiti: To some people it’s a form of popular modern art; to others it’s nothing more than the defacement of public property. It’s a phenomenon that is closely linked to the hip-hop scene, about which opinions have differed for more than two decades. The reason is that graffiti “artists” get the kick they are after only when their “pieces” are painted illegally. The removal of the “uncommissioned spray-can art” in Germany costs about 500 million euros every year. A good ten per cent of that cost is borne by Deutsche Bahn alone, whose cars and locomotives have always been a favorite target of these nocturnal spray paint attacks.

When the paint is dry, it is cleaned with a standard cleaner.

~~Is it art?~~
“Whether or not it’s art,” says Dr. Martin Melchiors, who is responsible for transportation coatings at the Bayer MaterialScience Coatings, Adhesives and Sealants Business Unit, “is a discussion which fortunately doesn’t really concern us. As a manufacturer of raw materials for modern coating systems – including graffiti-resistant coatings if required – the most important thing is to come up with innovative market solutions that meet the customer’s requirements. And because Deutsche Bahn isn’t the only company that wants to decide for itself what its vehicles should look like, we have done additional development work on our line of coating raw materials suitable for such applications.” As a result, graffiti doesn’t stand a chance with Bayhydur XP 2487/1, an innovative hardener for environmentally friendly, waterborne, two-component polyurethane coatings. Graffiti can now be removed from defaced surfaces faster, more easily and more effectively than from surfaces covered with conventional industrial coatings.

Test passed with flying colors! The spray paint can be wiped off easily. The new Bayhydur XP 2487/1 hardener from Bayer MaterialScience prevented the spray paint from penetrating into the underlying coating.

~~Reining in spray paint~~
The “trick” to this anti-graffiti coating is that the new hardener delays the penetration of the spray paint into the underlying coating. The deeper the spray paint can penetrate, the greater the ultimate damage. With waterborne coatings using new raw materials from Bayer MaterialScience, the penetrating action of graffiti colors or aggressive chemicals is slowed to the point that they can be easily wiped away. All this is achieved without the use of additives containing silicones or fluorine, ingredients in conventional coatings that have only temporary effects and are generally quite expensive. Standardized tests in the Bayer MaterialScience Coatings, Adhesives and Sealants laboratories have provided impressive proof of this.

~~A partner for the hardener~~
“In the light of the new European laws on the reduction of organic solvent emissions, with such special applications we are making a further contribution to the widespread use of environmentally friendly and high-performance coating systems,” says coatings expert Melchiors. And there’s more. With the polyol Bayhydrol XP 2470, Bayer MaterialScience has accompanied its innovative hardener with a powerful binder for waterborne, two-component polyurethane paints. This resin achieves an optimal crosslinking density and also guarantees high product quality even under extreme stresses. It also has a long-lasting shine. That is important because even with impressive environmental compatibility and durability, the overall performance of a coating system remains a decisive market criterion. The new anti-graffiti coatings naturally meet all these requirements.

Even marker pens don’t stand a chance against this solvent-free anti-graffiti coating. The “wipe test” proves it. On the other hand, the paint cannot be completely removed from solventborne two-component polyurethane coatings (right side).

~~Minimize cleaning costs~~
“First of all, of course, it is a question of minimizing the time and effort our customers have to spend removing graffiti, thus reducing the related costs,” says Melchiors. And then he adds with a wink, “Some graffiti spray paints even contain organic solvents, i.e. solvents that are not exactly environmentally friendly. Our graffiti-fighting products are therefore more environmentally friendly than many of the “works of art.” The cleaning crew, which previously had a tough time scrubbing graffiti off cars and underpasses, should now be at least equal to the task. And they are guaranteed to have fewer sore muscles in their arms.”