The glass beads will be spread on the paint soon after applying the paint. The road marking glass beads with a larger diameter can be seen on the surface, while the glass beads with a smaller diameter will be embedded in the paint. The add of road marking glass beads is essential for obtaining road paints with high retro reflectivity. If the glass beads cannot flow freely, it is impossible to disperse the glass beads in the paint. Due to the hydrophilic -OH groups on the glass surface, the moisture may cause small glass beads to agglomerate. The agglomeration can be prevented by modifying the surface of the glass beads with a hydrophobic coating. However, the adhesion between the coating on the glass surface and the paint should be strong. Otherwise, due to the friction, the glass beads can be easily removed in traffic. Therefore, when the road marking glass beads are coated with a hydrophobic material, the retro reflectivity will decrease. To overcome this problem, adhesives will be used in some cases. However, the adhesive will create a thick coating on the glass surface and the retro reflectivity will reduce again. In addition, the adhesive will cause agglomeration due to its hydrophilicity.
In the early stage when adding the paint and road marking beads, since the large glass beads can be easily seen on the paint surface, the retro reflectivity can be high. After the wheels roll over the paint, the paint and road marking glass beads begin to wear, which can result in a decrease in reflectivity. When the road marking glass beads are removed from the painted surface, the gap will be filled with dust. The result of this situation is that the paint will begin to darken and the visibility will decrease during the day and night. If the surface of the glass beads is not modified, the adhesion between the glass and the paint will become weak, and the glass beads will be easily removed from the paint surface. The state of the glass beads in the container is a group of colorless loose spherical particles. It is clean and free of debris, and should not have any agglomerate that do not fall apart after a light impact. Appearance requirements: Observed according to the method specified in this standard, the glass beads should be colorless and transparent spheres, smooth and round, no obvious bubbles or impurities in the glass beads.
The Use and Function of Glass Beads