Plastic films are used in many applications, including packaging, consumer goods, construction, transportation, and medical. Tear resistance is one of the properties that makes plastic films strong. It turns out that the durability of the material is crucial if it is subjected to a tear event. When testing the tensile strength of a film, tensile modulus and tear resistance are often used in combination to provide comprehensive information about its strength.

ASTM D1004 Test: 

The force to initiate tearing across a specific geometry of a film or sheeting specimen is measured using a constant rate of grip separation universal test machine, such as those listed below. The force necessary to initiate a tear is calculated from the resulting load-time or load-displacement data.

Tear resistance of plastic film or sheeting is a complex function of its ultimate resistance to rupture. The specimen geometry and speed of testing in this test method are controlled to produce tearing in a small area of stress concentration at rates far below those usually encountered in service. The test has its best utility and reliability for materials that do not have brittle failure or do not elongate greater than two hundred percent during testing.

Data from this test method are comparable only from specimens that vary no more than +/-10% from the nominal or average thickness of all specimens tested. And so the tearing resistance is expressed in maximum N (lbf) of force to tear the specimen.