The hardness of liquid silicone can be judged by the following methods:
1. Hardness test method
Shore hardness test method:
Shore hardness test method is a commonly used hardness test method for soft materials. During the test, the indenter is pressed on the liquid silicone sample with a certain pressure to measure the depth of the indentation. According to the indentation depth, the formula "Shore hardness = 100-E" can be used to calculate the hardness value, where E is the indentation depth. The higher the Shore hardness value, the higher the hardness of the liquid silicone.
ASTM D2240-00 standard hardness test method:
ASTM D2240-00 standard hardness test method is suitable for hardness measurement of hard materials. This method can be used when the hardness of liquid silicone is high. During the test, a standard indenter is used to press vertically on the surface of the sample to be tested under specified conditions, and the time taken for the indenter to recover from being pressed is measured as the hardness measurement value.
2. Selection of hardness tester
Shore hardness tester:
The hardness of liquid silicone is usually measured using a Shore hardness tester, especially a Shore A hardness tester. The Shore durometer is easy to operate and has accurate measurement characteristics, and is suitable for measuring the hardness of most liquid silicones.
Special durometer:
For liquid silicones with extremely low hardness (lower than Shore A0) or extremely high hardness (higher than Shore A90), a special durometer is required for measurement. For example, liquid silicones with a hardness lower than Shore A0 need to be measured using a Shore C durometer, while silicones with a hardness higher than Shore A90 use a Shore D durometer.
3. Precautions for hardness measurement
Sample preparation:
Before measurement, it is necessary to ensure that the liquid silicone sample has been fully cured. The hardness of incompletely cured silicone samples may not reach the expected level. At the same time, the thickness of the sample should not be less than 6mm to ensure the accuracy of the measurement. If the sample thickness is insufficient, no more than 3 layers of film can be stacked for measurement.
Measurement environment:
When measuring, it is necessary to carry out under standard environmental conditions to ensure the accuracy of the measurement results. Standard environmental conditions usually include a certain temperature and humidity range.
Operation specification:
When using a durometer for measurement, it is necessary to follow the correct operating method. For example, the pressure applied by the indenter and the measurement position of the indentation need to be strictly followed.
Instrument calibration:
The hardness tester needs to be calibrated regularly to ensure the accuracy of its measurement results. Calibration can be performed using a standard hardness block.
Result comparison:
It should be noted that the measurement results of hardness testers of different brands and models may differ. Therefore, when performing hardness measurement, it is necessary to clarify the model and brand of the hardness tester used, and communicate with customers or suppliers when necessary to ensure the accuracy of the measurement results.
In summary, judging the hardness of liquid silicone requires selecting appropriate hardness test methods and hardness testers, and following correct operating specifications and precautions. Through accurate hardness measurement, the physical properties and application characteristics of liquid silicone can be understood, providing strong support for product design and production.