Performance Evaluation of a Multifunctional Road Marking Coating for Tunnels Based on Nano SiO 2 and TiO 2 Modifications.

Multifunctional road marking coatings with the functions of high-temperature stability, degradation of exhaust gas, and self-cleaning are of great significance for the safe operation and environmental protection of tunnels. This article uses active acrylic resin and an organosilicon hydrophobic agent as the base material, selects expanded vermiculite and glass microspheres as insulation fillers, and uses ammonium polyphosphate, pentaerythritol, melamine, and aluminum hydroxide as high-thermal-stability systems to prepare a two-component road marking coating base material. Then, nano SiO₂ and modified nano TiO₂ are added as modifiers to prepare a multifunctional road marking coating for tunnels. The physical and chemical properties of multifunctional road marking coatings are evaluating based on laboratory tests including thermogravimetry and derivative thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, exhaust degradation, and contact angle tests. The results indicate that the developed multifunctional road marking coating effectively reduces the thermal conductivity of the carbon layer through physical changes in the flame retardant system and the heat resistance formed by the high breaking bond energy of nano SiO₂ during the combustion process. It forms a ceramic-like structure of titanium pyrophosphate with nano TiO₂ that is beneficial for improving flame retardancy without generating harmful volatile gases and has good flame retardant properties. N–V co-doping reduces the bandgap of TiO₂, broadens the absorption range of visible light by nano TiO₂, improves the catalytic efficiency of visible light, and achieves the degradation efficiency of the four harmful components NO_x, HC, CO, and CO₂ in automotive exhaust by 23.4%, 8.3%, 2.5%, and 2.9%, respectively. The solid–liquid phase separation in the multifunctional road marking coating in the tunnel causes the formation and accumulation of nano SiO₂ and TiO₂ particles on the coating surface, resulting in a microstructure similar to the "micro–nano micro-convex" on the lotus leaf surface and making a water droplet contact angle of 134.2° on the coating surface. [ABSTRACT FROM AUTHOR]