Film Appearance performance test film Hardness

Hardness is an important property of the mechanical strength of the coating film, and its physical meaning can be understood as the resistance of the coating film to another object with higher hardness acting on it. Test methods include pendulum damping hardness test method, Swart hardness method, Kleeman hardness method, pencil hardness method and Buckholz hardness method. From the perspective of the test method, a certain load is applied on a small contact area to measure the ability of the coating film to resist deformation. Therefore, the hardness of the coating film directly affects the scratch resistance and abrasion resistance of the coating. ability of light.

1. Determination of pendulum hardness

The principle of pendulum hardness measurement is that when the pendulum in contact with the coating swings at a certain period, the softer the coating is, the faster the swing of the pendulum attenuates. For method A in GB/Tl730-93, there are two types of adapters: Konig pendulum and Persoz pendulum. Before the Koenig pendulum is tested, the damping time of the pendulum from 6° to 3° should be corrected to (250±10)s on a standard glass plate. The Perthalz pendulum should be placed on a standard glass plate first, and the damping time of the connecting rod from 12° to 4° should be adjusted to at least 420s. Method B of GB/T 1730-93 uses double pendulums, and the swing time from 5° to 2° should be corrected to (440±6)s before the test, and the result is expressed as the ratio of the damping time on the coating surface to the damping time on the glass surface .

2. Determination of pencil hardness (GB/T6739-86)

Pencil hardness is measured by using a set of sharp edges on the end face of the pencil core with known hardness, and scratching the coating film at an angle of 45° to the coating film. It is expressed by the hardest pencil hardness that cannot scratch the coating film. There is a big difference in the difference between them, which can be tested with a special pencil Hardness Tester. When the pencil scratches the film, there are both pressure and shear force, which are different from the damping effect of the pendulum rod. There is no US conversion.

3. Other hardness testing methods

Swart hardness is measured by the number of times the metal ring swings back and forth on the paint film. The sensitivity is poor, but the test is faster than the joystick damping method. It is generally used for rough determination of the paint film. ), to see whether the coating film is scratched under a certain load, or expressed by the minimum load at which the coating film is scratched. There are manual and automatic Testers, and the arbitration test requires automatic testing (GB/T9279-88).

Buckholz hardness is an indentation test, which is only effective for hard coatings.

Hardness is usually determined by the pendulum method and the pencil hardness method. Pencil hardness is widely used because of its fast and convenient testing.