The test of rubber tear strength is carried out by tear test, and the test specimens of tear test are trouser, Delft, crescent and right angle. The preparation of the specimens is similar to that of the tensile specimens, with the following points being noted.
(1) When cutting the sample, the direction of the bisector of the tear angle of the cutter (tear direction) is consistent with the rolling direction.
(2) The number of samples shall not be less than 5.
(3) Use a thickness gauge with an accuracy of 0.01mm to measure the thickness of no less than 3 points in the test area of the sample, and take the median value as the thickness of the sample. The thickness value shall not deviate from 2% of the value taken. When comparing multiple groups of samples, the average thickness of each group of samples must be within 7.5% of the average thickness of each group of samples.
The steps for testing tear strength are as follows:
(1) Check equipment and instruments, prepare equipment and instruments, related tools, and clean up the environment;
(2) Start the machine and set relevant parameters (such as speed, mode, etc.);
(3) Clamp the sample to a certain depth in the upper and lower grippers and make it fully and evenly clamped in a parallel position. When carrying out the test of right-angle or crescent-shaped specimens, align the longitudinal axis of the specimen with the tensile direction and clamp it into the upper and lower grippers to a certain depth, so as to ensure sufficient and even clamping in the parallel position;
(4) After placing the sample on the clamping of the tensile testing machine, adjust the tensile machine (such as using a computer tensile machine, start the software to select the test method, set the parameter input size, etc.), start the testing machine, and adjust the test at the specified speed. The specimen is stretched until the specimen tears, and the maximum value is recorded.
Calculation of tear strength: T(SZ)=F/d; in the formula, "F" is the force when the sample is torn (the force value should be calculated according to the provisions in GB/T12833, take the median, unit: N) , "d" is the thickness of the sample (mm or cm), T is the tear strength (N/MM or N/cm).
At least 5 samples are required for each test sample, and the test results are expressed by the median, maximum and minimum values of the samples in each direction, and the data is accurate to the whole number. The single value and average value of each sample shall not be greater than 15%, and the number of samples shall not be less than 3 after selection.
