As a commonly used coating additive, leveling agent can promote the formation of a flat, smooth, and uniform coating film during the drying and film-forming process of the coating. There are also many types of leveling agents, how to realize their value for different types of leveling agents? This still needs to be tested. Next, the editor of Jianyi Chemical will introduce the experimental method of leveling agents to everyone!
Leveling agents are usually added to finished coatings because they only work in the liquid phase. The optimal dosage must be determined through a series of experiments using at least three different dosages to avoid producing undesirable side effects.
When completing a set of experiments, the solid content proposed by the manufacturer must be verified to ensure comparable results are obtained. The simulation of on-site construction conditions (brush coating, roller coating, and spray coating) and the substrate materials that will be used afterwards are recommended to ensure reliable data is obtained. In many cases, scraping two samples on the substrate involved, one thin and one thick, is enough to indicate the trend of surface defects in the coating.
A simple and applicable method is to pour the evenly mixed coating that meets the construction viscosity onto a flat plate tilted at 45 degrees, which is composed of a 100 micron thick polyester film laid on a glass plate. The flowing paint will form a wedge-shaped film.
In order to compare the effectiveness of different types of leveling agents, the surface defects of the coating can be visually inspected, such as sagging, cracks, streaks, orientation of the matting agent, bubbles, etc.
The surface tension can be measured using a drag ring method and a dyneimeter. Organosilicon leveling agents may have an impact on the formation of layered structures. A long layered structure always means that there will be no shrinkage due to contamination.
By using a syringe to drop different liquids onto a solid surface, the surface tension characteristics of the solid can be evaluated. The electroplating industry also uses such tests to test the level or degree of oil removal.
The recoating property (in the sense of rewetting) can be tested as follows: the first coat of paint (applied to a new substrate) is cured into a film in a temperature partitioned oven, with a temperature range 30-40 degrees Celsius higher than the standard curing temperature of the coating, and then a second coat of different thickness is sprayed. During the baking process, pinholes, shrinkage, and creep begin to appear, which is the critical temperature and limiting point of the coating thickness. Cross drawing and adhesive tape peeling tests can also be performed on these samples.
The above are several test methods for leveling agents, which should be added according to the current situation of the coating in practical applications.
