ASTM D1004_{Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting}

Test summary

This standard is designed to measure the force to initiate tearing in plastic films generally having a thickness less than 0.25 mm. Specimens are cut to a closely defined shape, ideally using a die cutter. The specimen geometry has been chosen to produce a stress concentration in a small area of the specimen. The cut specimens are put under tension in a test stand set at a constant rate of movement while the resultant tensile force is recorded. The maximum force in newtons and amount of elongation in mm are reported

Test apparatus

Die cutter

Micrometer reading to 0.0025 mm

Force testing stand

Suitable range loadcell compatible with the force testing stand

Preparation

Where conditioning is required, test specimens are stored at 23 ± 2° C, 50 ± 5 % RH for 40 hours.

Test method

If required, pre-condition the samples at 23 ± 2° C, 50 ± 5 % RH for 40 hours.

At least five samples are required. They may be cut perpendicular to the machine direction, or transvers to the machine direction of the sample material.

Specimens are cut, ideally using a die cutter, which is kept in good condition to ensure the cut specimens do not deviate by more than 0.5 % from the dimensions specified.

The thickness of the specimen is accurately measured in several points in the notched area and an average value calculated.

Specimens are clamped between the fixed (usually lower) grip, and the moving (usually upper) grip of the force testing stand.

The test stand is set in motion at a fixed crosshead speed of 51 mm/min.

After complete rupture of the specimen the maximum tensile load is measured, together with the maximum extension.

Calculate the mean maximum load and extension for all valid specimens tested in each principle direction of orientation.

Report

The test report shall contain:

All the information necessary for the complete identification of the sample

The average thickness of each specimen, and the average thickness of all test specimens

The average value of tear resistance calculated in newtons, and the maximum extension in mm, plus standard deviations of these averaged values