The sagging performance of paint is an important index for measuring thick build (thick film) paint. Due to the improper flow of the paint applied on the vertical surface, the uneven streaks and flow marks of the coating film are the sag phenomenon, which is reflected in the construction. The anti-sag performance is the maximum wet film thickness that the paint can make at one time. .
The national standard GB9264-88 stipulates the method for measuring the relative sagging performance of colored paints. The instrument used is composed of three multi-groove scrapers (test ranges are 50~275μm, 250 ~475μm, 450~675μm ) and a base. Each scraper can scrape the color paint to be tested into 10 parallel wet films of different thicknesses, the width of each wet film is 6mm, the distance between the strips is 1.5mm, and the thickness difference between adjacent strips The value is 25 μm.
There are the following steps and precautions during the test.
1. Put the glass plate on the appropriate position of the base.
2. Place the scraper on the top of the test panel, with the scale facing the operator.
3. Pour a sufficient amount of well-stirred sample evenly on the opening in front of the scraper applicator. Note that the two-component coating should be stirred evenly and have a certain potency and service life. The single-component coating should not allow the solvent to volatilize excessively.
4. Hold the two ends of the scraper applicator with both hands, make it scrape smoothly and continuously from top to bottom, and keep it straight without ups and downs, and complete this operation within 2~3s.
5. Place the test panel after scraping the coating film vertically immediately. Note that when placing the film, the film should be placed horizontally and "thin at the top and thick at the bottom", that is, the film with a horizontal direction and a small scale on the test plate should be placed on the upper end. When observing the reading, check the sagging situation. If the thickness of the film does not flow into the next thickness film, that is, when the dividing line is clear, the thickness of this film is the thickness of the wet film without sagging, in microns. Due to scraping, the area within 20mm at both ends of the coating film is not counted, and the dividing line in the middle of the film is observed.
The measurement of anti-sag performance can determine the dry film thickness and dosage of a film-forming coating. Generally, the anti-sag performance of thick-film coatings should be above 400 μm wet film, which can ensure the dry film thickness required for anti-corrosion. For some special types of primary film-forming coatings, its wet film can reach 1200 microns in one spray or squeeze, and its anti-sag test result is more than 1200 microns, and the scraper for judging the anti-sag performance of more than 600 microns needs to be customized to the manufacturer.
