For tear strength values, tensile testing machines are generally used for testing. What are the techniques for measuring tear strength values using tensile testing machines?

Continuously stretch rubber products with or without cuts at a specified speed until the rubber product is torn, in order to obtain the tear strength value. The tear strength value is generally related to the shape of the specimen, tensile speed, and test temperature.
1、 Select crescent shaped specimens:
The crescent shaped specimen is cut in advance to determine the force required for its expansion and tearing. The cutting, measurement, and testing of the specimen should be carried out continuously. If continuous testing is not possible, the specimen should be stored at the specified temperature for testing according to the specific situation. The interval between cutting and testing should not exceed 24 hours, and when conducting aging tests, cutting and testing should be done after aging.

2、 Select a right angled specimen without a cut:
The uncut rectangular specimen is a combination of tear initiation and tear propagation. The stress at the right angle point rises enough to cause initial tearing, and then the stress further increases until the specimen tears. However, only the total force required to destroy the specimen can be determined. Therefore, the measured force cannot be decomposed into two components that initiate tearing and propagate tearing.

3、 Select a right angled specimen with a cut:
A right angled specimen with a cut is made by pre cutting the specimen and measuring the force required for its expansion and tearing. However, it should be noted that the direction of the tearing cut should be consistent with the rolling direction, as the expansion speed of the spring testing machine is not directly related to the stretching speed, but is related to the cutting method and rolling direction of the specimen.

4、 Select pants shaped samples:
The use of pants shaped specimens is insensitive to the length of the incision, while strict control is required for the incision of the other two specimens. In addition, the obtained results are more likely to be related to the basic tearing ability of the material, and are less affected by tensile stress (generally ignored), and the tear propagation speed of the pressure testing machine is directly related to the tensile speed of the gripper.