Explanation

Also known as paint film. The ability of paint film to cover the color or color difference on the substrate. Represented in two ways: the minimum amount of paint required to cover a unit area, expressed in g/m2; Or the minimum paint film thickness required to cover the bottom surface,; The difference between the reflection coefficient of pigment and paint determines the covering power. The size of pigment particles and their dispersion in the paint are also important factors. There are several common test methods: ① unit area weight method, use a paint brush to evenly and quickly brush coatings on the glass plate with black and white spacing until the black and white grids can not be seen. Weigh the used coatings to get g/m2. The endpoint of this method is sometimes difficult to observe, and the flatness and brush marks of the product have an impact on its results. However, it is still widely used due to its simple operation and easy availability of equipment The minimum paint film thickness method is to use two black and white porcelain plates, with grooves and scales engraved on them, and a transparent glass slide plate covered to form a wedge-shaped space, so that the paint sample can move back and forth between them until the dividing line of the grooves on the porcelain plate can not be seen through the slide plate and the paint layer, and then the minimum paint film thickness can be calculated. This method uses less paint and has a fast testing speed, making it suitable for modern production control applications, but still mainly relies on visual inspection The contrast ratio measurement method is mainly applicable to white and light colored paints. It involves coating the sample with different thicknesses on a transparent polyester film, drying it, and placing it on a black and white glass plate. The reflectance is measured using an instrument to obtain the contrast ratio. When CR=0.98, it is considered fully covered and can be calculated based on the thickness of the paint film. This method accurately determines the endpoint, but the operation is more complicated.

Classification