Tear Strength Testing

Tear strength is an important mechanical measure of tear resistance, expressed as force divided by thickness, F/t. Product structure, loading method, and pull angle affect the measured value. It is a key physical property of rubber.

DIN ISO 34-1 addresses the mechanical properties, specifically tear strength, of vulcanized and thermoplastic rubber.

The standard specifies three methods for testing tear strength:

A. Trouser test specimen
B. Angle test specimen, with or without a notch
C. Notched crescent test specimen

Method A, the trouser tear test, is commonly used. The two legs of a slit strip specimen are pulled apart in a tensile tester. The maximum force required to tear the specimen is divided by its thickness, giving tear strength in kN/m.

The trouser specimen is preferred because the result is less sensitive to cut length. The other methods require careful control of the notch. Trouser-test results also relate more directly to fundamental tear behavior and are less affected by specimen length. Tear propagation rate is directly related to grip separation rate. Some rubbers, particularly natural rubber, exhibit irregular tear propagation that makes analysis difficult.

Tear strength depends on specimen shape, thickness, calendering direction, notch depth, test temperature, and tear speed.