In the coating industry, the hardness of the coating film is a key performance parameter, which directly affects the performance of the coating in different applications. The pendulum rod hardness test is a static measurement method used to measure the hardness of the film. This paper will introduce the principle and method of pendulum rod hardness test and its importance in coating industry.

principle
The pendulum rod hardness test is a test method based on the principle of viscoelasticity. Its core concept is to measure the hardness values of the film at different temperatures, but these values cannot be directly compared. In the hardness test of the pendulum rod, the swing attenuation of the pendulum rod is mainly affected by the absorption of mechanical energy by the film, which is called the loss modulus. The loss modulus is relatively low in both the glass region and the rubber region, and reaches its highest value at Tg (glass transfer temperature). The hardness of the pendulum rod is closely related to the thickness of the film, and the thin film may be affected by the substrate. This test method has the advantage that it does not destroy the film and is therefore suitable for quality control and research areas.

Coating hardness evaluation method: pendulum rod hardness test

instrument
In pendulum rod hardness testing, commonly used instruments include Konig pendulum (K pendulum) and Persoz pendulum (P pendulum). These two test instruments have been adopted by China’s national standard GB 1730 “Pendulum rod damping test for the determination of paint film hardness”.

K-pendulum: The test range of K-pendulum is from 6° to 3°. In the K-pendulum test, two steel balls are embedded under the cross bar of the pendulum rod, and these two steel balls are in contact with the coated template. By swinging the pendulum bar, applying pressure to the film, and then measuring the time required to swing from a larger Angle to a smaller Angle.

P-pendulum: The test range of P-pendulum is from 12° to 4°. The principle of the P pendulum is similar to that of the K pendulum, which evaluates the hardness of the film by measuring the time of the swing from a larger Angle to a smaller Angle.

Both test instruments are equipped with an optically controlled counting device that automatically records the damping time of the swing.

Coating hardness evaluation method: pendulum rod hardness test

Apply
Pendulum rod hardness testing has a wide range of applications in the coating industry:

Quality control: Manufacturers can use the pendulum hardness test to ensure that the hardness of the coating meets product standards and customer requirements, thereby providing high-quality coating products.

Performance evaluation: The pendulum rod hardness test helps to evaluate the wear resistance, scratch resistance, and other performance characteristics of the film, such as adhesion.

Coating selection: Manufacturers can choose the appropriate coating type and formulation according to the needs of different applications.

Coating durability: Knowing the hardness of the coating helps to predict its durability and life in actual use.

The result of the pendulum hardness test is affected by the test environment, film thickness and substrate material. Therefore, when testing, it should be carried out under controlled temperature and humidity conditions to ensure the accuracy of the test results.

Coating hardness evaluation method: pendulum rod hardness test

Sum up
Pendulum rod hardness test is an important test method used to evaluate the hardness of the film. It is widely used in the coatings industry to help manufacturers ensure product quality, evaluate film performance, and select suitable coatings for different applications. The principle of pendulum rod hardness test is simple, easy to operate, is one of the indispensable tools in coating engineering.