Anti-graffiti powder coating: "Invisible protective clothing" for urban public facilities

At a time when urbanization is accelerating, the cleaning and maintenance of urban public facilities has become an important issue. Graffiti not only destroys the beauty of the public environment, but also increases the cost of cleaning. In this context, anti-graffiti powder coating, as an innovative functional coating, has become a key technical means to solve the problem of urban graffiti with its unique performance advantages.

The core principle of anti-graffiti powder coating is to construct a hydrophobic and oleophobic microstructure by reducing the surface free energy. This coating is based on a polyester-polyurethane composite system, and a special process is used to form a micro-nano rough structure similar to a lotus leaf on the surface of the coating. When the liquid contacts the coating, due to the difference in surface energy, the liquid cannot infiltrate the surface of the coating, but forms spherical droplets that roll and slide, thereby taking away the stains attached to the surface. This physical mechanism makes it difficult for graffiti ink to adhere effectively. Even if a small amount of residue is formed, it can be easily removed by ordinary detergents or solvents without damaging the coating.

From the perspective of material formulation, the technological breakthrough of anti-graffiti powder coating is reflected in the innovative design of the resin system. Although pure polyester coatings have good mechanical properties, they are not resistant to stains; while polyurethane coatings have stain resistance, they are costly and have poor toughness. By compounding high hydroxyl polyester with blocked isocyanate in a specific ratio, the chemical resistance and hardness advantages of polyurethane are retained, and the toughness and adhesion of the coating film are improved by polyester. This synergistic effect allows the coating to have good weather resistance and mechanical properties while maintaining anti-graffiti performance.

The microstructure of the coating is a key factor in determining the anti-graffiti performance. Studies have shown that when the surface roughness of the coating reaches a certain threshold, the increase in the solid-liquid contact area will enhance the liquid-repellent effect. This seemingly contradictory phenomenon stems from the dynamic balance of surface energy - the rough structure increases the energy threshold required for liquid infiltration, so that the surface energy of the coating is always lower than the critical value required for liquid infiltration. This design concept is highly consistent with the self-cleaning effect of lotus leaves in nature. By simulating the microscopic morphology of biological surfaces, the super-liquid-repellent performance of artificial coatings is achieved.

In terms of application performance, anti-graffiti powder coatings show significant advantages. The hardness of the coating can reach more than 2H pencil hardness, and the impact resistance has passed the GB/T 1732 standard test, showing resistance to mechanical damage. The chemical resistance test shows that the coating has no change after being immersed in a 5% hydrochloric acid solution for 168 hours, and the surface is not damaged after being wiped with acetone 10 times. These performance indicators ensure the long-term stability of the coating in the outdoor environment, and can effectively resist the influence of natural factors such as ultraviolet radiation and acid rain erosion.

The optimization of the construction process is an important link to ensure the performance of the coating. The coating adopts electrostatic spraying technology, the construction temperature range is 130-200℃, and the curing time is 20 minutes. The following points should be noted during construction: the oil stain on the surface of the substrate must be thoroughly cleaned before spraying; the spraying thickness must be controlled within the range of 60-80μm; the trace gas generated during the curing process must be collected through the exhaust gas treatment system. The precise control of these process parameters is directly related to the density and surface quality of the coating.

Anti-graffiti powder coatings have a wide range of applications, covering municipal facilities, public transportation, education and medical care and other fields. After coating the surface of outdoor benches, bus stops, lamp posts and other facilities, the frequency of cleaning and maintenance can be significantly reduced; when used in hospital furniture, laboratory equipment and other scenarios, its chemical resistance can effectively resist disinfectant erosion; in the coating of electronic equipment shells, it can provide long-lasting anti-fouling protection. This multifunctional property makes it an indispensable protective material in modern urban construction.