The tear strength of thermoset rubbers, thermoplastic elastomers, and silicones can be measured according to specification ASTM D624. The test measures the strength required to initiate a tear in a material. D624 describes multiple different types of sample shapes that can be tested in a standard universal testing machine (tensile testing machine). Usually materials that are tested to D624 are also tested according to specification ASTM D412 to measure the tensile strength and elongation. If you are going to perform this test, you should read the entire specification from ASTM. This is a quick summary to decide if this test is right for you, and to point out what equipment you need to perform the test.
This video shows how to perform a tear strength test:
Cut or injection mold your material into one of the tear shapes shown in the specification. Specimen B and C are the most common.
Measure the width of the specimen
Load the specimen into tensile grips.
Begin the test by separating the tensile grips at a speed of 20 inches per minute
End the test after sample break (rupture)
Tear Strength – lb/in unit. (Peak load observed during test / thickness of material)
Equipment required (same as ASTM D412 machines):
1. Universal testing machine (tensile testing machine) with these minimum specifications:
Servo-controlled to keep a constant rate of speed during the test of at least 20in/min (+/- 2 inches/min)
At least 30 inches of crosshead travel or more for high elongation materials
Most small and common 1kN (225 pound) are fine for this test (see ADMET eXpert 7601).
2. Software or suitable electronics are required to operate the machine and to take the measurements. Basic systems will provide the raw data, and stress-strain charts. Using these sources of data, you can calculate tear strength yourself (peak load / material thickness). However, fully PC based systems have the capability to calculate all of these automatically such as our MTESTQuattro testing software which has built in support for ASTM D624. Using this system would provide you with the tear strength immediately after performing the test.
3. Tensile grips hold your specimen during the test as it is being pulled apart. Rubbers and elastomers usually lend themselves to being easily held in a variety of grip designs such as manual vise grips, pneumatic grips, wedge grips, or eccentric roller designs.
Click here if you are also interested in ASTM D412 tensile strength and elongation testing.