When using a Shore A hardness tester to test the hardness of silicone, the minimum thickness of the sample pressing sheet must be 6mm. If the sample thickness is less than 6mm, the test requirements can be met by stacking films of the same material to a total thickness of ≥6mm (no more than 3 layers and the films must be tightly fitted).
The reasons are analyzed as follows:
Standard requirements: According to the Shore hardness test standard, when using a Shore A hardness tester to measure hardness, the sample thickness should be at least 6mm. This requirement is intended to ensure that the pressure needle can be fully pressed into the sample during the test to avoid the support (such as the test bench) from generating a reaction force on the pressure needle due to the thin sample, thereby affecting the accuracy of the test results.
Test principle: The Shore hardness test reflects the material hardness by the depth of the pressure needle pressing into the sample surface. If the sample is too thin, the pressure needle may penetrate the sample or touch the support, causing the test value to deviate from the true value. Therefore, the minimum thickness of 6mm is the key to ensuring the reliability of the test results.
Thin sample processing: For silicone samples with a thickness of less than 6mm, the test can be performed by stacking films of the same material to a total thickness of ≥6mm. However, please note:
The number of stacked layers should not exceed 3 to avoid the gap between layers affecting the test results.
The films should fit tightly together to ensure that the pressure needle presses into a single material layer rather than the interface between layers during the test.
Test conditions: In addition to the thickness requirements, the test environment (such as temperature and humidity) and the surface condition of the sample (such as flatness, no bubbles, no mechanical damage) will also affect the test results. Therefore, before testing, it is necessary to ensure that the sample is placed in a standard environment (such as a temperature of 18-28°C) for a sufficient time to eliminate the influence of environmental factors on hardness.