National standard methods include: GB/T1726-79 "Determination of Coating Hiding Power", and factory practical analysis methods include: brushing method.
method points
The minimum amount of paint used to evenly paint the paint on the surface of the object so that the base color no longer appears, expressed in g/m2.
Instruments and materials
①Width of the paintbrush is 25~35mm, ②The weight of the balance is 0.01g.
③ Black and white grid glass plate Cover one end of the 100mmX250mm glass plate by 100mmx50mm (reserved for hand holding during the test), and then spray a layer of black nitro paint on the remaining 100mmX200mm area. After drying, use a knife to cut out 25mmx25mm squares at intervals, then soak the glass plate in water for a while, take it out to dry, peel off the square paint film at intervals, and then spray a layer of white nitro paint to form a 32-square shape. Black and white spaced glass plates, and then paste a piece of smooth kraft paper, scrape a layer of epoxy glue (to prevent the solvent from penetrating and destroying the black and white grid paint film), that is, a strong black and white grid board is made.
④ Wooden dark box 600mmX500mmX400mm, inside the black box is divided into upper and lower parts with 3mm thick frosted glass, and the ground surface is downward to make the light source uniform. Two 15W fluorescent lamps are evenly installed in parallel on the upper part of the dark box, a light baffle is installed in the front, the front of the lower part is open for inspection, and the inner wall is painted with matte black paint.
Analysis steps
According to the viscosity specified in the product standard, weigh the total mass of the cup and paintbrush containing the paint on a balance with a sensitivity of 0.0 lg.
Use a paint brush to evenly paint the paint on the black and white grid glass plate. In the dark box, 15~20cm away from the frosted glass sheet, the end with the black and white grid is inclined at an angle of 30°~45° to the plane, and observe under the fluorescent lamp. End with the black and white squares just out of sight, and paint quickly and evenly, and the paint brush should not be placed on the edge of the board.
Weigh the cup and paintbrush filled with remaining paint to find the quality of the paint on the black and white grid. (Related instrument: Opacity plate)
calculate
In the formula, X is the hiding power of the paint in the sample, g/m2;
m1—the total mass of the cup and paintbrush filled with paint before painting, g;
m1—the total mass of the cup and paintbrush filled with remaining paint after painting, g;
S—painted area of black self-grid panel, cm2, take the arithmetic mean of the results of two parallel tests as the measurement result.
measurement error
The difference between the results of two parallel tests shall not be greater than 5% of the arithmetic mean.
