Drawing method test principle [with schematic diagram]

There are two specific methods for testing adhesion, and the procedure for loosening the bond between the paint film and the substrate is fairly similar (Figure 6.6). In one approach, film separation is achieved with a sharp knife, pushed along the interface with precisely measured force.

While this seems like a simple test method, the peeling process is actually complex, involving shear stress and tensile stress, which eventually lead to the disintegration of the film. In addition, a leverage effect plays a role in the detachment of the coating, and the strength of this effect can be characterized by the angle at which the force acts on the film.

Figure 6.6 Adhesion measurement setup based on the layering procedure.

Figure 6.7 Effect of Mechanical Paint Film Properties on Knife Cut Test Results

In knife cutting, the principle of removing paint film is similar to machining metal on a lathe. A specific power system becomes effective here. It consists of the rake angle of the knife, the thickness of the coating, the friction between the knife and the coating and the substrate, the energy stored elastically in the film and the energy loss caused by plastic deformation, the fracture energy that occurs during the decomposition process in the film, and other secondary factors. desired impact.

To obtain meaningful results, all of these parameters should be tightly controlled, or at least their impact estimated as accurately as possible. In many cases, however, the details of the separation process show.