Coating Drying time for painting mass evaluation

The paint drying time measurement method is divided into the surface drying event and the actual drying time. There are several methods for measuring the drying time:

Determination of Surface Drying Time

Method A (blowing cotton ball method) Gently put a cotton ball on the surface of the paint film, and blow the cotton ball along the horizontal direction with your mouth 10-15cm away from the cotton ball. If it can be blown away and there is no cotton thread left on the membrane surface, it is considered to be dry on the surface.

Method B (finger touch method) lightly touch the surface of the paint film with your fingers, if you feel a little sticky, but no paint sticks to your fingers, the surface is considered to be dry.

Actual Drying Time Determination

Method A (press filter paper method) put a piece of (15mmX15mm) qualitative filter paper (smooth surface in contact with the paint film) on the paint mold, gently place the dry Tester (weight 200g, bottom area lcm²) on the filter paper, start the stopwatch at the same time, after 30s, Take away the drying Tester, turn the sample over, the filter paper can fall freely, or tap a few times on the back with your fingers, the filter paper can fall freely and no paper fibers remain on the paint film, which is the actual drying.

Method B (cotton ball pressing method) put a degreased cotton ball on the paint film, gently put a drying Tester on the cotton ball, and start the stopwatch at the same time, after 30 seconds, remove the drying Tester and cotton ball, and the sample rotates After 5 minutes, observe that there are no traces of cotton balls on the paint film and the phenomenon of loss of light. If there are 1-2 cotton threads left on the paint film, which can be picked up and flicked off with a cotton ball, it is considered that the paint film is actually dry.

Regarding the division and test methods of the drying process, there are great differences in national standards. Such as ASTMD1640-95. The drying process is divided into 8 stages; ISol517 uses the 125-250μm glass bead falling ball method to measure the surface dryness. No imprint on operation, test with 1000g weight (GB/T9273-88).

To observe the entire drying process continuously, an automatic drying time Tester can be used . The instrument uses the motor to drive the gear through the reduction box, and walks linearly on the paint film at a slow speed of 30mm/h. The whole process takes 24 hours. As the paint film gradually dries, the gear track gradually changes from deep to shallow until it disappears. .Recently, the uniform movement of the stylus is used to make a stylus track on the paint film, and the drying process is evaluated according to the change of the track (as shown in the figure)