Anti-Graffiti Coating
The following report appeared in The State newspaper March 04, 2018.
For the second week in a row, vandals have struck churches with vulgar graffiti about the late Billy Graham. Sunday, it was discovered that the Upward Baptist Church in Henderson County, N.C. was the latest target of vandalism.
Church members at the congregation in Flat Rock arrived Sunday morning to find vulgar and offensive language spray painted on the church building, according to multiple reports.”
It’s a real problem – graffiti.
We are not talking about the messages themselves. That is another subject.
We are chemists. What we are talking about is the unwanted and often unlawful painting, writing and generally defiling surfaces owned by someone else.
In modern times, paint (particularly spray paint) and marker pens have become the most commonly used graffiti materials.
In most countries, marking or painting property without the property owner’s permission is considered defacement and vandalism, which is a punishable crime.
And graffiti-based vandalism is on the rise in the United States, costing an estimated $112 billion in annual cleanup expenses. Although urban areas face the most issues, graffiti is found in all areas of the country.
When it gets down to chemistry and physics, graffiti is simply this; one coating applied to another coating. Because paints and inks are designed to stick to the underlying surface, graffiti becomes permanent once the paint dries.
It then becomes very difficult and costly to remove. Harsh chemicals and pressure washing is often used to remove graffiti but can damage the underlying paint. In addition, it is extremely labor intensive.
To combat the problem, anti-graffiti coatings have been developed.
There are two different categories. The first, sacrificial coatings that form a clear coat barrier over the wall or surface being protected. If the surface is vandalized the coating can be removed (sacrificed) using a high-pressure washer taking the graffiti with it. The coating must then be reapplied. Materials used to make sacrificial coatings are usually inexpensive optically clear polymers such as acrylates, biopolymers, and waxes. These polymers form weak bonds with the substrate to allow for easy removal. But they need to be reapplied.
The second type is the permanent coatings. These are often more expensive than sacrificial coatings, but if used appropriately they only have to be applied once. These work by creating a protective surface that spray paint cannot bond to. After the surface has been vandalized, solvents or manufacturer-supplied cleaners are used to remove the graffiti. The underlying surface and the protective coating should remain undamaged. Some of the types of permanent coatings include those based on polyurethanes, nano-particles, fluorinated hydrocarbons, or siloxanes.
NanoSlic
NanoSlic is in the category of permanent anti-graffiti coatings. It uses a primary binder polymer that is ceramic, and largely composed of silica. As the coating cures, highly non-polar molecules align themselves in such a way to form the coating’s surface. Unlike other anti-graffiti coatings, the surface is both hydrophobic and oleophobic, similar to polytetrafluoroethylene (Teflon) and is completely resistant to all types of paints and inks. Any paint that does remain is easily washed away.
Below this layer, the bulk of the coating polymerizes into an inert silica-based structure. At the substrate surface, the polymer chemically bonds to hydroxyl groups on the substrate. The advantage of this approach is that a high degree of adhesion and abrasion resistance is achieved to almost any surface.
The resulting coating is highly resistant to all types of graffiti materials. In addition, NanoSlic anti-graffiti coatings are capable of maintaining properties under adverse conditions such as sunlight, humidity, chemicals, and abrasion. It can be viewed as an ultra-protective topcoat, offering a graffiti-proof surface. Clear gloss or matte versions enhance or maintain the underlying coating’s aesthetics.