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Test summary
The test can be used to compare the propagation resistance of various plastic films and sheeting of comparable thickness. Standard sized specimens are separated by a slit of half the length of the sample resulting in two “legs” which are torn apart at a constant speed while the tensile force is measured
Test apparatus
Die cutter or cutting apparatus.
Micrometer reading to 0.0025 mm
Force testing stand
Suitable range loadcell compatible with the force testing stan
Test method
1. If required, pre-condition the samples as specified in ISO 291.
2. At least five samples are required.
3. Specimens are cut, ideally using a die cutter. Sample may be cut in the longitudinal or transverse direction of the sample
4. The thickness of the specimen is accurately measured in mm in several points, and an average value (d) calculated.
5. Specimens are clamped with one “leg” in each of the grips of the force testing stand which are initially set 75 mm apart.
6. The test stand is set in motion at a fixed crosshead speed of 200 or 250 mm/min.
7. Continue the test until the tear has propagated through the entire length of the entire unslit length of the sample.
8. Measure the mean load (Ft) over a 50 mm interval of the tear disregarding the first 20 mm and final 5mm portions of the force/distance curve.
9. Calculate the Tear resistance from the formula
Tear resistance = Ft/d - report as newtons/mm
Report
The test report shall contain:
All the information necessary for the complete identification of the sample including direction if appropriate and standards atmosphere used for pre-conditioning if appropriate.
The test speed used
The average thickness of each specimen.
Report the arithmetic mean of at least five samples from each set of test specimens, in newtons/mm