Determination of automotive coating hardness

The hardness of the coating is one of the important properties that characterize the mechanical strength of the coating. At present, pendulum hardness test methods are commonly used to determine the hardness of automotive coatings. The pendulum hardness can be divided into two types: single pendulum type and double pendulum type. The former measurement value is expressed in seconds, and the latter is expressed as a percentage of glass hardness.

The single pendulum is also known as Koenig and Pessaz pendulum hardness. Most foreign large-scale automotive paint manufacturers use these two hardness testers. The hardness indexes of their automotive coatings, especially topcoats, are often expressed in terms of these two hardnesses, such as Mascus, Storac, and Akzo. The working principle of several pendulum damping tests is basically the same, that is, if the pendulum rod contacting the coating surface oscillates at a certain period, the softer the surface, the faster the attenuation of the pendulum rod attenuates, whereas the slower the attenuation. In general, the Kony Road hardness value is about half of the value of the P. Because the structure, weight, size, swing period and amplitude of various pendulum rods are not the same, the interaction between the pendulum rod and the coating also depends on the elasticity and viscoelasticity of the coating itself. The result of the measurement cannot be established in relation to each other. Therefore, when the pendulum hardness value of the coating is listed in the product standard, the type of the pendulum instrument used must be specified at the same time.

Double swing pendulum hardness tester is commonly used in China. Its result is expressed as the ratio of the damping time of the swing attenuation within the specified swing range to the damping time of the swing attenuation within the same swing angle range on the glass plate. The glass pendulum must be calibrated before the double pendulum hardness tester.