Film - Determination of impact strength (impact tension and impact Hardness)

Impact strength is meaningful for the identification of paint films subjected to mechanical impact during use. All paint films for automobiles, railways, urban transportation, and paint films for lathes and machines belong to this type of paint film. However, the evaluation of the impact strength of the coating film is also of great significance for all other coating films, because we are describing the problem related to the impact load, that is, the significant increase of the applied load; The general test under static load is different.

It is well known that increasing the speed of the applied load, that is to say of the deformation, can lead to a situation different from that which occurs to the material under static loading.

For example, materials (metals, plastics, etc.) that undergo plastic failure under static tests may show brittle failure upon impact (impact brittleness). Such materials are often referred to as impact brittle to distinguish them from brittle materials which tear without significant residual deformation in a static test (at elongation). During the impact test, there is often a tendency for the brittleness of the material to increase. (Related instrument: impact Tester)

The deformation of polymer materials, especially paint films, not only depends on the tension, but also depends on the action time. When the deformation is slow, the paint film can relax, and the degree of deformation will be great.

When the deformation speed increases, the paint film has no time to relax, and its degree of deformation decreases, and when the speed (impact) is very large, the elastic paint film may become rigid and brittle under static load. As pointed out earlier, these relaxation phenomena play a large role in the behavior of high rings, so they need to be taken into account when testing any mechanical properties of the coating film. Paint films can be applied on substrates (metal, wood, etc.) that bend or do not bend at impact. In the former case, the impact tension of the paint film is tested according to the dynamic tension of the metal; in this case, the destruction of the paint film depends on its elasticity and its adhesion to the substrate. In the latter case, when bending of the metal is not visible, the impact hardness of the paint film should be observed, which depends on its elasticity, adhesion and its static hardness.

Measuring the impact tension and impact hardness of the paint coating (related instruments: Hardness Tester), in addition to measuring other mechanical properties, can also obtain a fairly complete technical identification of its mechanical strength.