Tear strength is simply the force it takes to rip a plastic film. Tear strength is commonly used for testing stretch film and other plastics. An Elmendorf tear test is commonly used to find the tear strength. One end of the sample stretch film is held in a fixed clamp and the other end is attached to a pendulum. A small cut is made in the edge of the stretch film. The pendulum is then released and the force required to continue the tear is measured.
Tear strength is commonly measured in grams per mil of gauge (.002 in.). Most stretch films have a high elongation and therefore have better tear resistance. Tear resistance is important because it helps to measure protective values of the stretch film, as well as strength required to open the stretch film when torn open.