The paint can change its viscosity with the change of temperature. For example, when the ambient temperature is around 30°C, the viscosity of the paint will decrease compared with that at normal temperature. When it exceeds 35°C, there will be another change, because the temperature is too high. The solvent in the paint volatilizes faster, which will thicken the paint, especially the paint containing a lot of low-boiling solvents. Because the solvent volatilizes too fast, the surface of the film layer is dried too fast during construction, and severe orange peel, pinholes, Dry grains and so on are considered diseases. When the temperature is lower than 5°C, the paint will be falsely thickened, misleading the construction, and the thinner will cause sag or the dry film is too thin. When the temperature is lower than 0°C, the water-based method will freeze and be scrapped. The oil-water separator in the tank also affects the construction due to freezing. In order to ensure smooth construction and coating quality, the environment temperature of 15~25°C is the best condition.
Relative humidity is also directly related to construction and film quality. For coating construction, a good relative humidity should be 45%~65%. When the relative humidity exceeds 65%, the solid surface of the material will adhere to a thickness of about The water film of 0.001-0.01µm, the humidity increases, the water film thickens, some data show that solids have adsorption force to gas, the adsorption force is different for different materials, because the capillary diameter of general materials is 0.01-0.0001µn, and the water vapor The particles are smaller, so moisture is easily absorbed. Liquids can wet solids. During the wetting process, the attraction between solid molecules and liquid molecules is stronger than the attraction between liquid molecules itself, which means the surface water and water permeability of solids.
The water vapor attached to the solid surface plays the role of separating it from the film layer. For coatings, not only is there solid-to-gas adsorption, but also because it contains solvents, especially solvents with low coating points. The volatilization of the solvent will absorb the heat on the surface of the solid body, so that the temperature of the solid surface will drop. When the relative humidity exceeds 80%, the water vapor will condense on the solid surface to form "hoarfrost", which will seriously damage the quality of the film layer. When the relative humidity is lower than 45%, the climate is too dry, and because of the electrostatic effect caused by the rapid spraying of the material and the impact with the workpiece during spraying, the surface of the film layer absorbs dust. The consequences of these dust are not only the film layer The appearance is not beautiful, and it is an important factor that accelerates the pulverization and damage of the film layer.
