The traditional solvent-based crack paint has three principles: reducing the amount of binder, increasing the amount of pigment and filler, and improving the volatility of solvent. The crack paint made by these principles has greater shrinkage and lower flexibility, and the tensile strength is higher due to internal stress, forming uniform cracks and exposing the color of primer at the cracks. The crack paint formed by this principle does not need special requirements for the matching background paint, but only needs to meet the general matching principle of solvent-based paint. However, this traditional solvent-based crack paint is not only fragile, but also has poor adhesion. The surface of crack paint must be coated with a layer of varnish to prevent it from falling off.
In addition to performance defects, solvent-based crack paint also uses a lot of organic solvents, which not only pollutes the environment, but also causes fire and explosion hazards and harms the health of operators. Therefore, many countries have been studying water-based crack paints recently. Japan has developed a kind of asbestos board crack paint, with organic paint as primer and inorganic phosphate paint as crack topcoat after drying. Cracks are formed by high shrinkage caused by the surface tension difference of inorganic phosphate coating on organic coating. The surface of this crack paint is bright and hard, which has the vision and feel of ceramic tiles, and can overcome the defect that the phosphate coating of asbestos board turns white when it meets water.