Adhesion determination (circling method)

At present, the test methods for measuring the adhesion of the coating film include the circle method, the grid method, the cupping method (see the cupping test), etc. The circle method is introduced as follows.

The circle method is to evaluate the fastness or adhesion of the coating film to the substrate according to the integrity of the coating film within the scratch range of the circular rolling line, expressed in grades.

equipment

Specifications of relevant parts of the adhesion Tester:

The screw pitch of the test bench is 1.5mm, and its rotation is synchronous with the rotating needle. The 35 brand stylus is used, and weights can be placed on the load plate. The weight is 100, 200, 500, 1000g. Radius value is 5.25mm, 4x magnifying glass .

experiment procedure

Test under the test conditions of 23±2°C and relative humidity of 50±5%.

Check the needle of the adhesion Tester before the measurement, and replace it if it is not sharp. When measuring, make the tip of the rotating needle touch the coating film, shake the handle clockwise evenly, the rotation speed is within the range of 80∽100 rpm, and the length of the circular rolling line scratch pattern is 7.5±0.5mm. If the scratches do not expose the bottom plate, add weights as appropriate until the bottom plate is exposed. Scratches were inspected and graded with a 4x loupe .

result

Take the upper surface of the sample scratch as the inspection target, and mark seven parts such as 1, 2, 3, 4, 5, 6, and 7 in turn. Correspondingly divided into seven levels. Check the completeness of the coating film of each part in order. If more than 70% of the grids of a certain part are intact, the be intact, otherwise it should be considered damaged. For example, if the coating film of part 1 is intact, the adhesion is very good, which is rated as the first grade; if the coating film of part 1 is damaged and the part 2 is intact, the adhesion is next, which is rated as the second grade, and so on, and the seventh grade is the worst adhesion .

The results are subject to the same level of at least two samples.