Coating sagging and Leveling

Leveling

Leveling refers to the ability of the coating film to flow from an irregular and uneven surface to a flat and smooth surface after the coating is applied. The national standard GB1750 79 (88) "Measurement Method for Leveling of Coatings" stipulates that there are two methods for measuring leveling property: brushing method and spraying method. Expressed in points.

The determination method of the brush coating method is to adjust the sample to the construction viscosity according to the provisions in the "General Preparation Method of Paint Film", brush it on the tin plate to make it smooth and even, and then use a brush to wipe the middle part of the coating film longitudinally. Once brush marks, observe how long it takes for the brush marks to disappear and the coating film to return to a smooth surface. Whether it is qualified or not is regulated by the product standard. Generally, a coating film with good leveling property can be leveled within 10 minutes. Spraying method Observe the time for the painted surface to be uniform, smooth, wrinkle-free and orange-peel free, and evaluate whether it is qualified according to product standards.

The US ASTMD2801-69 (81) method for testing the leveling property of coatings stipulates that the leveling test scraper with several gaps of different depths be used to scrape the coating into parallel strip coatings with different thicknesses, and observe the complete and partial flow to The number of shape coats, compared with the standard graphics, is represented by 0~10 grades, 10 grades represent complete leveling, 0 grades represent the worst leveling, suitable for thousands of white and light-colored paints.

Sagginess

When the liquid paint is painted on the vertical surface, affected by the gravity, the surface of the wet film will flow down, resulting in the phenomenon that the upper part of the paint film becomes thinner and the lower part becomes thicker, and in severe cases, it forms a spherical or corrugated shape. There are three reasons for the paint film to sag: the flow characteristics of the paint are not suitable; the coating is too thick, exceeding the limit of the possible thickness of the paint; the coating environment and construction conditions are not suitable.

my country's national standard GB9264 88 "Determination of Sag Properties of Paints" stipulates that the sag properties of paints are measured by a Sag Tester. Apply a certain thickness of coating film on the test plate, place the test plate vertically, observe the flow and fall of the wet film, record it, and check whether it meets the product standard.